GMI PSS1250-HS-7-48-D Instruction Manual

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
SIL 3 Power Supply System PSS1250(-HS)-7-48-D
48 Vdc - 50 A,
19’’ Rack with 4 power modules PSM1250
and diagnostic module PSO1250
PSS1250-HS-7-48-D, PSS1250-7-48-D
INSTRUCTION & SAFETY MANUAL
G.M. International s.r.l.
20852 Villasanta MB Italy

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
2
Index
SIL 3 Power Supply System PSS1250(-HS)-7-48-D 48 Vdc - 50 A
19’’ Rack with 4 power modules PSM1250 and diagnostic module PSO1250
General Characteristics .............................................................................................................................................................................3
Technical Data...........................................................................................................................................................................................3
PSO1250 supply information .....................................................................................................................................................................3
Features.....................................................................................................................................................................................................4
Ordering Information..................................................................................................................................................................................4
Hot Swapping capability.............................................................................................................................................................................5
Active Ideal Diode-OR circuit.....................................................................................................................................................................6
Output voltage setting, Fault indications, Diagnostic information ..............................................................................................................6
Warning......................................................................................................................................................................................................6
Storage ......................................................................................................................................................................................................6
Disposal .....................................................................................................................................................................................................6
Functional Diagram for PSS1250-HS-7-48-D or PSS1250-7-48-D............................................................................................................7
Functional Safety Manual and Applications (for models with HS) .............................................................................................................8
Functional Safety Manual and Applications (for models without HS) ......................................................................................................10
Testing procedure at T-Proof...................................................................................................................................................................12
System Composition................................................................................................................................................................................12
Installation Procedure - 1st step - Back Panel installation for PSS1250-xx-7-48-D-W (wall mounting into a cabinet) ............................12
Installation Procedure - 2nd step - Wiring of AC input lines, faults, modbus terminal blocks on Back Panel PCB (PSS1250-xx-7-48-D)13
Installation Procedure - 3rd step - Rack unit installation on Back Plane for PSS1250-xx-7-48-D-W (wall mounting into a cabinet).......14
- Installation of PSS1250-xx-7-48-D-F (frontal rack mounting into a cabinet) ......................................15
Installation Procedure - 4th step (for models with HS) - Section A : HS setup ........................................................................................16
- Section B : Installation & start up of PSO1250.................................................17
- Section C : HSC red LED signalling test..........................................................17
- Section D : Installation and pre-start up of PSM1250 ......................................18
- Section E : Wiring of 1st&2nd PSM1250 negative DC out lines ......................19
- Section F : Wiring of 5th&6th PSM1250 positive DC out lines & PSS start-up 20
Installation Procedure - 4th step (for models without HS) - Section A: Installation & start up of PSO1250.............................................21
- Section B: Installation and pre-start up of PSM1250.......................................22
- Section C: Wiring of 1st&2nd PSM1250 negative DC out lines ......................23
- Section D: Wiring of 5th&6th PSM1250 positive DC out lines & PSS start-up 24
Shutdown and Disconnecting Procedure of PSM1250 power module from the Rack unit: - for models with HS ....................................25
- for models without HS................................25
Replacement Procedure of PSM1250 power module from the Rack unit (for models with or without HS)..............................................25
PSO1250 Diagnostic Module: features and set up..................................................................................................................................26
Supported Modbus parameters: functions and details.............................................................................................................................31

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 AG.M. International ISM0528-1 3
General Description:
The Power Supply System type PSS1250(-HS)-7-48-D is an
anodized aluminum 19” Rack unit (4U high) suitable for 4 plug-in Power Supply Modules type PSM1250 and 1 Overview module type PSO1250 for diagnostic functions.
Four PSM1250 are divided in two groups and each group is composed by 2 PSM1250 with paralleled outputs and with load sharing circuits which distribute current load equally to each
PSM1250 to increase reliability and reduce internal power dissipation. Therefore, each group provides 24Vdc and 50 A output with redundancy. Two groups have their outputs connected
in series by internal copper bar, therefore PSS1250(-HS)-7-48-D system provides 48Vdc and 50 A output with redundancy. The system accepts up to two independent AC power sources
with nominal voltage range 110 to 240 Vac (±10%). Four configurations of 19” Rack Units are available with or without Hot Swapping: two for wall mounting and two for frontal rack mount-
ing, always into a cabinet. For more information about different configurations see page 4.
Hot Swap Plug-ins:
When using rack PSS1250-HS-7-48-D, each PSM1250 power supply module can be placed without disturbing Power Supply operations.
Diagnostic:
Rack PSS1250(-HS)-7-48-D, accept a plugin module (PSO1250) dedicated to monitoring all diagnostic functions of each power supply, via a front panel touch screen LCD color display
which indicates Input/Output Voltage, Current and Power; Input Line Frequency; Output current sharing percentage related to each group; Internal Temperature; alarm status. RS485
Modbus output provides full diagnostic and status conditions. PSO1250 presence or fault does not affect PSS1250 operation and functional safety application.
Overvoltage protection:
Each PSM1250 module has got 3 independent overvoltage protections: 1 voltage limiting loop at 30 Vdc and 1+1 crowbars at 30 Vdc.
Therefore, PSS1250(-HS)-7-48-D system has 60 Vdc upper limit as maximum overvoltage protection value, considering series connection between overvoltage protections of both
PSM1250 module groups.
EMC:
Fully compliant with CE marking applicable requirements.
High load fuses breaking capability:
In case of short circuit on the load, the Power supply system delivers a very high peak current (about 800 Amp) for a duration of 0.5 ms.
This characteristic ensures the instant breakage of the protective fuse or circuit breaker. Because of the very short peak current duration, other equipment connected to the load are not
affected by the failure event and continue to operate without interruption.
Functional Safety Management Certification:
G.M. International is certified by TUV to conform to IEC61508:2010 part 1 clauses 5-6 for safety related systems up to and included SIL3.
Technical Data
General characteristics
Supply:
AC Input voltage: nominal 110 to 240 Vac (±10%), with frequency range 48 to 62 Hz.
Power Factor Correction (full load): 0.95 typ.@230Vac, 0.99 typ.@115Vac, 4 PSMs ; 0.98 typ.@230Vac, 0.995 typ.@115Vac, only 2 PSMs: 1st & 5th OR 2nd & 6th.
Efficiency @48Vdc out (full load): ≥85 % @ 230 Vac , ≥82.5% @ 115 Vac, 4 PSMs ; ≥89 % @ 230 Vac , ≥86% @ 115 Vac, only 2 PSMs: 1st & 5th OR 2nd & 6th.
Max. internal power dissipation @48Vdc out (full load): 425 W @ 230 Vac , 505 W @ 115 Vac, 4 PSMs ;
305 W @ 230 Vac , 395 W @ 115 Vac, only 2 PSMs: 1st & 5th OR 2nd & 6th.
AC input current (sinusoidal at full load) @48Vdc out: 30 A @100Vac, 25.7 A @115 Vac, 13 A @230 Vac, 4 PSMs ;
28.4A @100Vac, 24.4 A @115 Vac, 12.1 A @230 Vac, only 2 PSMs:1st & 5th OR 2nd & 6th.
Inrush current (each PSM): 37Apk @ 264Vac; 32Apk @ 230Vac; 16Apk @ 115Vac.
AC input connection: screw terminal blocks suitable for 4mm2wires on back panel pcb.
Isolation (Test Voltage):
Input to Output isolation: 2500 Vrms (routine test).
Input to Earth-Ground isolation: 1500 Vrms (routine test).
Earth-Ground to Output isolation: 500 Vrms (routine test).
Output or Earth-Ground to Fault contact isolation: 500 Vrms (routine test)
Output:
Output voltage: 48 Vdc (adjustable from 42 to 56 Vdc) for whole system. Each PSM1250 output is 24 Vdc (adjustable from 21 to 28 Vdc).
Regulation: 0.4 % for a 100 % load change.
Stability: 0.01 % for a 20 % line voltage change.
Ripple: ≤250 mVpp.
Output current: 50 A nominal (@48Vdc out).
Output power: up to 2400 W nominal (@48Vdc out), max 2600 W nominal (@56Vdc out).
Output Rise Time: 2.5 s.
Dynamic Response: 2 ms for 0-100% load change (overshoot ±1.5% of Vout setting).
Connection: M6 screw terminals on copper bars suitable for lug (at least 6.5 mm hole diameter) with 16mm2wire on back panel pcb.
Hold-up time (AC in) at full load: 40ms (4 PSMs), 20ms (only 2 PSMs:1st & 5th OR 2nd & 6th).
Over voltage protection: each PSM1250 output is limited to 30 Vdc plus two redundant crowbars for over voltage protection at 30 Vdc.
Therefore, PSS1250(-HS)-7-48-D output is upper limited to 60 Vdc maximum value.
Power good signaling:
Output good: 19.5 V ≤Vout ≤29.5 V (see page 6 for more information).
Indication: via LCD touch screen on PSO1250 and Modbus RTU RS-485 protocol.
Signaling: voltage free SPST normally energized relay (contact closed), de-energize in over/under voltage conditions (contact open).
Contact Rating: 2 A 50 Vac 100 VA, 2 A 24 Vdc 48 W (resistive load).
Connection: screw terminal blocks suitable for 1.5 mm2 wires on back panel pcb.
Compatibility:
CE mark compliant, conforms to Directive: 2014/30/EU EMC, 2014/35/EU LVD, 2011/65/EU RoHS.
Environmental conditions:
Operating temperature limits: -40 to +70°C de-rated linearly 65-70% load above 50°C (see on next page the Power Output vs. Ambient Operating Temperature diagram).
Relative humidity limits: 95 %, up to 55 °C.
Transport, storage temperature limits: - 45 to + 85 °C. Max altitude: 2000 m a.s.l.
Approvals:
SIL 3 / SIL 2 conform to IEC 61508:2010 Ed. 2.
SIL 3 Functional Safety TÜV Certificate conforms to IEC61508:2010 Ed.2, for Management of Functional Safety.
Mechanical:
Mounting: 19” Rack unit for wall mounting or for frontal rack mounting, into a cabinet.
Weight: 19” fully equipped about 20 Kg, with 4 PSM1250 and 1 PSO1250 module.
Location: installation in Safe Area/Non Hazardous Locations.
Protection class: IP 20, Open Type.
Dimensions: see drawings on pages 12, 14 and 15.
PSO1250 supply information
Supply:
AC Input voltage (each AC terminal block): nominal 110 to 240 Vac (±10%), with frequency range 48 to 62 Hz.
AC input current (sinusoidal): 45 mA @ 100 Vac input voltage, 40 mA @ 115 Vac input voltage, 15 mA @ 230 Vac input voltage.
Inrush current: 1.6 A peak @ 264 Vac; 1.4 A peak @ 230 Vac; 0.7 A peak @ 115 Vac.

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
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Features
SIL 3 for NE Load according IEC 61508:2010 (see page 8 (with HS model) and page 10 (without HS model)).
SIL 2 for ND Load according IEC 61508:2010 (see pages 9 (with HS model) and pages 11 (without HS model)).
Systematic capability SIL 3.
2 universal AC Input Lines, nominal 110 to 240 Vac (±10%) (48 to 62 Hz).
Power factor correction.
Hot swappable modules.
EMC Compatibility to EN61000-6-2, EN61000-6-4.
TÜV Functional Safety Certification.
Highly regulated output of 48 Vdc - 50 A, due to 24 Vdc out for each PSM1250 module.
Under and over voltage alarm monitoring, for each PSM1250 module.
3 over voltage redundant protections, for each PSM1250 module.
For each group, redundant parallel connection of PSM1250 modules with load sharing.
Reduces Power dissipation (in parallel/redundant configuration of each group)
by replacing a Schottky diode with Mosfet Active Ideal Diode.
89% efficiency @230 Vac input and 48 Vdc output and full load.
PSM1250 fan speed control depending on ambient temperature and output power.
High load fuse breaking capability without interrupting operations.
19” Rack unit, 4U high,anodized aluminium, durable metal enclosure.
Tropicalization for electronic components.
Modbus RTU RS-485 diagnostic output.
Rack unit & Back panel Back Panel PCB Configuration Hot
Swapping Ordering code of PSS1250 NOT included rack slot items
wall mounting into a cabinet
19 inches wide rack
1 output 48 Vdc up to
50 A with redundance
1 diagnostic module
(optional)
YES PSS1250-HS-7-48-D-W PSM1250 : needed 4 pieces
plugged into 4 slots
(1st & 2nd + 5th & 6th)
PSO1250 : 1 piece (optional)
plugged into 7th slot
MCHP228 : needed 2 pieces
plugged into 3rd & 4th slots
+
1 piece plugged into 7th slot
if PSO1250 is not required
wall mounting into a cabinet
NO PSS1250-7-48-D-W
frontal rack mounting into a cabinet
19 inches wide rack
1 output 48 Vdc up to
50 A with redundance
1 diagnostic module
(optional)
YES PSS1250-HS-7-48-D-F
frontal rack mounting into a cabinet
NO PSS1250-7-48-D-F
PSM1250 : needed 4 pieces
plugged into 4 slots
(1st & 2nd + 5th & 6th)
PSO1250 : 1 piece (optional)
plugged into 7th slot
MCHP228 : needed 2 pieces
plugged into 3rd & 4th slots
+
1 piece plugged into 7th slot
if PSO1250 is not required
Ordering Information
Valid for Input Voltage nominal
range 110 to 240 Vac (±10%)
Photos Ordering code of rack slot items
Needed 4 pieces of PSM1250
power supply module with
24 Vdc – 50 A output
1 piece of PSO1250 (optional)
diagnostic module with
touch screen LCD color display
Needed 2 pieces of MCHP228
blank panel to fill
not used 3rd and 4th rack slots
+
1 piece of MCHP228 to fill 7th slot
if PSO1250 is not required

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 AG.M. International ISM0528-1 5
Hot swapping capability
PSS1250-HS-7-48-D Power Supply System with Hot Swapping (HS) capability is able to provide power and it is fully protected from the Hot Swapping of any power, or diagnostic,
module. This protection system operates for both the insertion and disconnection of the modules.
When inserting the module, the mains voltage is only applied when mechanical and electrical module connections are completely and correctly positioned, while before
disconnecting the module the external electrical connections have to be at zero voltage level.
To achieve this result, a sophisticated 1oo2 mechanical and electrical protection circuit, using micro switches (MS), relays (REL) and special hot swapping circuits (HSC), has been
designed. All power modules have a mains terminal block for Line-Neutral-Earth/Ground, placed in the back panel pcb that can be used for two independent mains lines (AC1 & AC2).
The Line and Neutral are connected to the power module via two couples of 1oo2 series contact relays, driven from hot swapping circuit according to closed or open state of 1oo2
series mechanical switches. Two micro switches for each power module are placed in the front part of the 19” Rack unit and are activated (closed) by front panel top screws used to fix
the module at rack. For each power module, 4 relays are installed on the back panel pcb, close to the mains terminal blocks, in 1oo2 architecture for safety purposes.
For further safety, close to the relays, for each position, there is a red LED. Before inserting a power module, the operator must verify that related red LED is OFF.
If the red LED is turned ON, a failure is present on a couple of series relays or HS controller circuit could be damaged and no power module shall be inserted and fixed in that position.
The opening of the micro switches, operated by unscrewing at least one of two front panel top screws, initiates the following two actions:
1. Mains line is disconnected from the power module, because hot swapping circuit de-energizes relays, opening their contacts;
2. Voltage on the power module connectors is brought to 0 volts, to avoid any sparking possibility. This is done by a MOSFET solid state switch (SSS) connected in series with the
active ideal diodes (AID), which disconnects the output from the DC output bus. The internal voltage in the disconnected power module remains completely isolated from the
output connections and therefore, even if an operator shorts the connections with a screw driver or any other tool, this will not generate a spark.
When a power module is inserted and fixed to rack unit by its screws, the MOSFET solid state switch remains open until the power supply starts to operate correctly, then it closes
itself applying voltage to the load.
PFC PWM
L
N
AC 1
AID SSS
HSC
REL
PFC PWM
L
N
AC 2
AID SSS
Load
-
+
48 Vdc
Legend:
AC1: Mains line
AC2: Mains backup line
PFC: Power Factor Controller (1st stage)
PWM: PWM Controller (2nd stage)
HSC: Hot Swappable Circuit
AID: Active Ideal Diode
SSS: Solid State Switch
MS: Micro switches on rack unit
REL: Relays on back plane pcb
L: Line
N: Neutral
MS
HSC
MS
+
PSM1250 (1st Module)
PSM1250 (2nd Module)
-
REL
PFC PWM
L
N
AC 1
AID SSS
HSC
REL
PFC PWM
L
N
AC 2
AID SSS
MS
HSC
MS
+
PSM1250 (5th Module)
PSM1250 (6th Module)
-
REL
24 VDC 1st Group
24 VDC 2nd Group

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
6
Reasons for using an Ideal Diode-OR Controller circuit, in N+1 redundant power supply applications with high availability systems
High availability systems often employ power supply modules connected in parallel to achieve redundancy and enhance system reliability.
ORing diodes have been a popular means of connecting these supplies at a point of load. The disadvantage of this approach is the forward voltage drop and resulting efficiency loss.
This drop reduces the available supply voltage and dissipates significant power.
Replacing Schottky diodes with N-channel MOSFETs reduces power dissipation and eliminates the need for expensive heat sinks or large thermal layouts in high power applications.
In the Ideal Diode-OR Controller circuit (active ideal diode), the voltage across source and drain is monitored by IN and OUT pins, and GATE pin drives the MOSFETs to control their
operation. In effect the MOSFET source and drain serve as the anode and cathode of an ideal diode.
In the event of a power supply failure, for example if the output of a fully loaded supply is suddenly shorted to ground, reverse current temporarily flows through the MOSFETs that are
ON. This current is sourced from any load capacitance and from the other supplies. The active ideal diode quickly responds to this condition turning off the MOSFETs in about 0.5µs,
thus minimizing disturbance and oscillations to the output bus.
Using Oring diodes to parallel two 24 VDC power supply modules of each group for redundancy, one Schottky diode is used for each module. The voltage drop across the diode can
reach about 0.8 V at 50 A, this means about 40 W dissipation for each module. For each group, if two 50 A paralleled modules are used for full 50 + 50 A redundancy, a total power of
about 80 W is dissipated for this purpose, but there are two groups of PSM1250 modules, so that total dissipation will be 160 W. This reduces efficiency, reliability and increases space
for heat sinks. Moreover, in case of module failure, diodes take time to recover and consequently they do not preserve the load from transients during the backup operation.
To avoid all these problems G.M. International has introduced, in the new PSS1250 Power Supply System, the use of active ideal diodes.
The MOSFETs resistance for active ideal diodes is about 1.2 mΩresulting in 3.6 W dissipation for each power module. For each group, if two 50 A paralleled modules are used for
full 50 + 50 A redundancy, a total power of about 2 x 7.2 W = 14.4 W is dissipated for the purpose resulting in about ten times less dissipation compared to Schottky diodes solution.
This increases efficiency, reliability, availability and reduces space for heat sinks.
This circuit provides also very smooth voltage switchovers without oscillations with fast turnoff, minimizing reverse current transients.
For each PSM1250 power module, the output voltage can be set to 24 Vdc + 18%; -14% via a front panel trimmer (see page 18 (for system with HS) or page 22 (for system without
HS) for more information about voltage adjust procedure). Therefore, for whole PSS1250(-HS)-7-48-D system, the output voltage can be set to 2 x 24 Vdc = 48Vdc + 18%; -14%.
For each PSM1250 power module, under voltage threshold is set to 19.5 V, while Over voltage threshold is set to 29.5 V.
A front panel power ON green LED signals mains voltage is applied to the power module and normal DC output voltage is present on DC output screw terminals.
Power module Fault conditions are signaled by opening contact of NE relay (contact closed in normal condition), positioned on back panel pcb “Fault” terminal block.
Faults can be:
 Under voltage Vout < 19.5 V.
 Over voltage Vout > 29.5 V.
In absence of under / over voltage fault, the green Power ON LED is ON if output voltage is within 19.5 V - 29.5 V range.
If output voltage goes below 19.5 V, the green Power ON LED blinks and holds this condition as long as output voltage goes over 20 V.
If output voltage goes over 29.5 V, the green Power ON LED is OFF and holds this condition as long as output voltage goes below 29 V.
After under / over voltage fault, coming back to normal condition, the green Power ON LED is ON if output voltage is within 20 V - 29 V range.
Communication with four power modules is achieved via PSO1250 diagnostic module, which incorporates a front panel color touch screen. The diagnostic module is able to query each
power modules (using an internal proprietary bus) and read data such as, Input/Output Voltage, Current and Power; Input Line Frequency; Output current sharing percentage related to
each group; Internal Temperature; alarm status (under/over out voltage, AC line absence, internal PFC or PWM stage in OFF state, internal high temperature, fans malfunctioning).
This information is available via front panel touch LCD and externally via Modbus RTU on related wall mounting terminal block. Alarm status of one or more power modules is signalled
by opening contact of NE relay (contact closed in normal condition), positioned on back panel pcb “Comm. Fault” terminal block. The diagnostic module does not interfere with the
Power system functional safety. The power system can perfectly work without the diagnostic module and any failure of the diagnostic module does not affect system performance,
reliability and SIL level of Functional Safety applications.
About PSS1250(-HS)-7-48-D fault indication, it’s important to connect in series the Fault relay contacts of: the 1st and the 5th PSM1250 modules (which define the 1st 48V generator);
the 2nd and the 6th PSM1250 modules (which define the 2nd 48V generator). When a PSM1250 module goes in fault condition which reflect a fault condition on related 48V generator.
Both series connections (one for each 48V generator) of Fault relay contacts should be connected to Safety PLC inputs to read status of these contacts and detect possible faults.
For more information about how to connect Fault relay contacts, please see next Functional Safety applications on pages 8 to 11.
Output voltage setting - Fault indications - Diagnostic information
Warning
Storage
Disposal
PSS1250(-HS)-7-48-D is isolated Switching Power Supply unit located in Safe Area or Nonhazardous Locations within the specified operating temperature limits
-40°C ≤Tamb ≤+70°C and mounting conditions. Read installation manual before operating the unit. PSS1250(-HS)-7-48-D must be installed, wired, operated and maintained
only by qualified personnel, in accordance to the relevant national/international installation standards, following established installation rules.
Green Power ON LED of PSM1250 power module: check that green LED is OFF before screwing out PSM1250 module front panel. Red LED (one for each PSM1250 slot position,
only for system with HS capability) on wall mounting panel board: connect a PSM1250 power module to the rack unit only if corresponding red LED on back panel board is in OFF
state. This equipment is an open-type device and is meant to be installed in an enclosure suitable for the environment such that the equipment is only accessible with the use of a tool.
The enclosure provides, according to EN60529, an IP20 minimum degree of protection (or similar to NEMA Standard 250 type 1). The equipment shall only be used in an area of at least
pollution degree 2, as defined in IEC 60664-1. The end user is responsible to ensure that the operating temperature of the module is not exceeded in the end use application.
Units must be protected against dirt, dust, extreme mechanical (e.g. vibration, impact and shock) and thermal stress, and casual contacts.
All circuits connected to PSS1250(-HS)-7-48-D must comply with the overvoltage category II (or better) according to EN/IEC60664-1.
Electrostatic Hazard: the enclosure of PSS1250 series must be cleaned only with a damp or antistatic cloth.
Any penetration of cleaning liquid must be avoided to prevent damage to the unit. Failure to properly installation or use of the equipment may risk to damage the unit or severe personal
injury. The unit cannot be repaired by the end user and must be returned to the manufacturer or his authorized representative. Any unauthorized modification must be avoided.
If after an incoming inspection the unit is not installed directly on a system (parts for spare or expansion with long storage periods) it must be conveniently stocked.
Stocking area characteristics must comply with the following parameters. Temperature -40 to +70 °C, the -45 to +80 °C is meant for limited periods, -10 to +30 °C is preferred.
Humidity 0 to 95 %, 0 to 60 % humidity is preferred. Vibration: no prolonged vibration should be perceivable in the stocking area to avoid loosening of parts or fatigue ruptures of
components terminals. Pollution: presence of pollutant or corrosive gases or vapors must be avoided to prevent corrosion of conductors and degradation of insulating surfaces.
The product should not be disposed with other wastes at the end of its working life. It may content hazardous substances for the health and the environment, to prevent possible harm
from uncontrolled waste disposal, please separate this equipment from other types of wastes and recycle it responsibly to promote the sustainable reuse of material resources.
This product should not be mixed with other commercial wastes for disposal.

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 AG.M. International ISM0528-1 7
SAFE AREA,
NON HAZARDOUS LOCATIONS
Function Diagram Dual AC Supply wiring architecture for PSS1250-HS-7-48-D or PSS1250-7-48-D:
PSS1250-HS-7-48-D or PSS1250-7-48-D, dual AC supply, 1 redundant 48 Vdc - 50 A Output, PSO1250 overview module
Series of two groups, each with two paralleled PSM1250 modules, to provide full redundancy on AC lines (AC1 and AC2) and one 48 Vdc - 50 A redundant output.
Back Panel PCB of PSS1250-HS-7-48-D with Hot Swapping circuits:
Back Panel PCB of PSS1250-7-48-D without Hot Swapping circuits:
A
C 1
A
C 2
L
N
L
N
-
+
DC
LCD
touch screen
color display
48 Vdc, 50A + 50 A
AC1 AC2AC AC ACAC
-
PSO1250PSM1250PSM1250PSM1250PSM1250
+
FLT FLT FLT FLT
COM.
FLT
Modbus
...
-+-+-+
AC1 and AC2 earth lines
can be connected
together or
use the same wiring.
1st slot of rack
1st Group
24 Vdc
2nd slot of rack 5th slot of rack 6th slot of rack
48Vdc, 50A (+ 50 A redundancy)
2nd Group
24 Vdc
3rd and 4th slots of rack
cannot be used because
they are not connected
to AC input & DC output

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
8
Functional Safety Manual and Application
1) Application with HS capability and NE output load
Failure category Failure rates (FIT)
λdd = Total Dangerous Detected failures 11.72
λdu = Total Dangerous Undetected failures 5.66
λsd = Total Safe Detected failures 0.00
λsu = Total Safe Undetected failures 189.08
λtot safe = Total Failure Rate (Safety Function) = λdd + λdu + λsd + λsu 206.46
MTBF (safety function) = (1 / λtot safe) + MTTR (8 hours) 553 years
λno effect = “No Effect” failures 12165.06
λnot part = “Not Part” failures 1068.36
λtot device = Total Failure Rate (Device) = λtot safe + λno effect + λnot part 13439.88
MTBF (device) = (1 / λtot device) + MTTR (8 hours) 8.5 years
PFDavg (TI = 1 year) = λdu * (0.5*8760 + 8)h + λdd * 8h 2.493E-05
λsd λsu λdd λdu SFF DCD
0.00 FIT 189.08 FIT 11.72 FIT 5.66 FIT 97.26% 67.43%
Failure rates table according to IEC 61508:2010 :
Failure rate table:
Safety Function and Failure behavior: PSS1250 with HS and 2+2 PSM1250 modules is considered to be operating in Low Demand mode, as a Type A module, having Hardware Fault
Tolerance (HFT) = 1 or redundant configuration 1+1 on input/output. Its failure behaviour for NE output load is described by the following definitions:
□Fail-Safe State: it is defined as the system output going below 4 Vdc. Internal diagnostics detect and notify Low/High (Under/Over voltage) fails (DD) to logic solver, which can
operate to convert these fails to the fail-safe state, requiring to turn off all malfunctioning power supplies and to replace them with new PSM1250 modules.
□Fail Safe: failure mode that causes the system to go to the defined fail-safe state without a demand from the process.
□Fail Dangerous: failure mode that does not respond to a demand from the process (i.e. being unable to go to the defined fail-safe state), so that the system output voltage is
blocked or oscillating between 4 and 40 Vdc or above 60 Vdc, and both internal diagnostics cannot detect and notify faults to logic solver.
□Fail High - Overvoltage: failure mode that causes the system output to go above 60 Vdc. Internal overvoltage protections try to limit system output voltage < 60 Vdc,
otherwise internal crowbars trip to fail safe state for system output ≥60 Vdc. Internal diagnostics detect and notify High fail to logic solver, which does not automatically trip on
this failure, classified as Dangerous Detected (DD).
□Fail Low - Undervoltage: failure mode that causes the system output to go between 4 and 40 Vdc. Internal diagnostics detect and notify Low fail to logic solver, which does not
automatically trip on this failure, classified as Dangerous Detected (DD).
□Fail “No Effect”: failure mode of a component that plays a part in implementing the safety function but that is neither a safe failure nor a dangerous failure, so that the system
output voltage is deviated between 40 and 60 Vdc. When calculating the SFF, this failure mode is not taken into account.
□Fail “Not part”: failure mode of a component that is not part of the safety function but part of the circuit diagram and is listed for completeness. When calculating the SFF, this
failure mode is not taken into account.
The PSO1250 diagnostic module does not interfere with power system functional safety. The power system can perfectly work without diagnostic module and any failure of the
PSO1250 diagnostic module does not affect system performance, reliability and SIL level of this Functional Safety application. Failure rate data are from Siemens Standard SN29500.
Description: In normal operation 2+2 PSM1250 modules are powered by connecting AC1 input supply to two modules and AC2 input supply to other ones by means of related terminal
blocks on the Back Panel PCB (see previous functional diagram for more information). The 1st and 5th PSM1250 fault relay contacts must be connected in series to Safety PLC or Safe-
ty logic solver. The 2nd and 6th PSM1250 fault relay contacts must be connected in series to Safety PLC or Safety logic solver. Each power supply internal diagnostic uses this contact
to notifies under/over voltage module faults to logic solver, which can require to turn off this power supply and to replace it with a new PSM1250 module.
In absence of module fault the relay contact is closed, while in presence of module fault the relay contact is open. Green Power ON LED of each PSM1250 is lit with AC input presence
The outputs of the 1st and 2nd PSM1250 modules are already paralleled on the Back Panel PCB by specific copper bars, in order to give the 1st Group output.
The outputs of the 5th and 6th PSM1250 modules are already paralleled on the Back Panel PCB by specific copper bars, in order to give the 2nd Group output.
The positive (+) pole of the 1st Group output is already connected (by specific copper bar on the Back Panel PCB) to the negative (-) pole of the 2nd Group output, in order to connect in
series two groups and to get 48 Vdc output. Therefore, the NE output load is connected (by related output copper bars with screw terminals on the Back Panel PCB) between
the negative (-) pole of the 1st Group output and the positive (+) pole of the 2nd Group output, that is 48 Vdc power system output.
In normal condition, NE output load is Normally Energized (NE). In absence of one only AC input supply (AC1 or AC2), two PSM1250 modules are shutdown (their fault relay contacts
are open) but the other ones operate in normal condition, so that output load is normally energized.
In absence of both AC input supplies (AC1 and AC2), 2+2 PSM1250 modules are shutdown (their fault relay contacts are open) and output load is de-energized (Safe State).
T[Proof] = 4 years T[Proof] = 20 years
PFDavg = 9.97E-05 Valid for SIL 3 PFDavg = 4.99E-04 Valid for SIL 2
PFDavg vs T[Proof] table, with determination of SIL supposing module contributes 20% of entire safety function:
PFDavg vs T[Proof] table, with determination of SIL supposing module contributes 10% of entire safety function:
T[Proof] = 8 years T[Proof] = 20 years
PFDavg = 1.99E-04 Valid for SIL 3 PFDavg = 4.99E-04 Valid for SIL 2
Systematic capability SIL 3.
L
N
L
N
-+
...
-+-+-+
FLT
AC
AC1
DC NE Output Load
+
PSM1250
Module Position
number 1
LCD
touch screen
color dislpay
PSO1250
-
AC2
FLT
AC
FLT
AC
FLT
AC
PSM1250
Module Position
number 2
PSM1250
Module Position
number 5
PSM1250
Module Position
number 6
Fault 2+6
Fault 1+5
AC2
AC1
Safety
PLC
input Safety
PLC
input
COM FLT Modbus
1st Group
1st and 2nd modules 2nd Group
5th and 6th modules
48 Vdc, 50A (+ 50A redundancy)

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 AG.M. International ISM0528-1 9
Functional Safety Manual and Application
2) Application with HS capability and ND output load
Failure category Failure rates (FIT)
λdd = Total Dangerous Detected failures 7.64
λdu = Total Dangerous Undetected failures 198.82
λsd = Total Safe Detected failures 0.00
λsu = Total Safe Undetected failures 12165.06
λtot safe = Total Failure Rate (Safety Function) = λdd + λdu + λsd + λsu 12371.52
MTBF (safety function) = (1 / λtot safe) + MTTR (8 hours) 9 years
λnot part = “Not Part” failures 1068.36
λtot device = Total Failure Rate (Device) = λtot safe + λno effect + λnot part 13439.88
MTBF (device) = (1 / λtot device) + MTTR (8 hours) 8.5 years
PFDavg (TI = 1 year) = λdu * (0.5*8760 + 8)h + λdd * 8h 8.72E-04
λsd λsu λdd λdu SFF DCD
0.00 FIT 12165.06 FIT 7.64 FIT 198.82 FIT 98.39% 3.70%
Failure rates table according to IEC 61508:2010 :
Failure rate table:
Safety Function and Failure behavior: PSS1250 with HS and 2+2 PSM1250 modules is considered to be operating in Low Demand mode, as a Type A module, having Hardware Fault
Tolerance (HFT) = 1 or redundant configuration 1+1 on input/output. Its failure behaviour for ND output load is described by the following definitions:
□Fail-Safe State: it is defined as the system output going between 40 and 60 Vdc. Internal diagnostics detect and notify High (Over voltage) fails (DD) to logic solver, which can
operate to convert these fails to the fail-safe state, requiring to turn off malfunctioning power supply and to replace it with new PSM1250 module.
□Fail Safe: failure mode that causes the system to go to the defined fail-safe state without a demand from the process.
□Fail Dangerous: failure mode that does not respond to a demand from the process (i.e. being unable to go to the defined fail-safe state), so that the system output voltage is
blocked or oscillating between 0 and 40 Vdc or above 60 Vdc, and internal diagnostic cannot detect and notify faults to logic solver.
□Fail High - Overvoltage: failure mode that causes the system output to go above 60 Vdc. Internal overvoltage protection tries to limit output voltage < 60 Vdc, otherwise
for output ≥60 Vdc internal crowbars trip, turning off malfunctioning power supply. Internal diagnostics detect and notify High fail to logic solver, which does not automatically trip
on this failure, classified as Dangerous Detected (DD).
□Fail Low - Undervoltage: failure mode that causes the system output to go between 0 and 40 Vdc. This failure mode is dangerous, but internal diagnostic notifies Low fail to
logic solver, which cannot convert this failure to the fail-safe state but it can only require to turn off malfunctioning power supply and to replace it with a new PSM1250 module.
□Fail “Not part”: failure mode of a component that is not part of the safety function but part of the circuit diagram and is listed for completeness. When calculating the SFF, this
failure mode is not taken into account.
The PSO1250 diagnostic module does not interfere with power system functional safety. The power system can perfectly work without diagnostic module and any failure of the
PSO1250 diagnostic module does not affect system performance, reliability and SIL level of this Functional Safety application. Failure rate data are from Siemens Standard SN29500.
Description: In normal operation 2+2 PSM1250 modules are powered by connecting AC1 input supply to two modules and AC2 input supply to other ones by means of related terminal
blocks on the Back Panel PCB (see previous functional diagram for more information). The 1st and 5th PSM1250 fault relay contacts must be connected in series to Safety PLC or Safe-
ty logic solver. The 2nd and 6th PSM1250 fault relay contacts must be connected in series to Safety PLC or Safety logic solver. Each power supply internal diagnostic uses this contact
to notifies under/over voltage module faults to logic solver, which can require to turn off this power supply and to replace it with a new PSM1250 module.
In absence of module fault the relay contact is closed, while in presence of module fault the relay contact is open. Green Power ON LED of each PSM1250 is lit with AC input presence
The outputs of the 1st and 2nd PSM1250 modules are already paralleled on the Back Panel PCB by specific copper bars, in order to give the 1st Group output.
The outputs of the 5th and 6th PSM1250 modules are already paralleled on the Back Panel PCB by specific copper bars, in order to give the 2nd Group output.
The positive (+) pole of the 1st Group output is already connected (by specific copper bar on the Back Panel PCB) to the negative (-) pole of the 2nd Group output, in order to connect in
series two groups and to get 48 Vdc output. Therefore, the ND output load is connected (by related output copper bars with screw terminals on the Back Panel PCB) between
the negative (-) pole of the 1st Group output and the positive (+) pole of the 2nd Group output, that is 48 Vdc power system output. In normal condition, absence of both AC input
supplies (AC1 and AC2) implies that 2+2 PSM1250 modules are shutdown (their fault relay contacts are open) and output load is Normally De-energized (ND). In presence of one only
AC input supply (AC1 or AC2), two PSM1250 modules are shutdown (their fault relay contacts are open) but the other ones are correctly turned on, so that output load is energized (Safe
State). In presence of both AC input supplies (AC1 and AC2), 2+2 PSM1250 modules are correctly turned on and output load is energized (Safe State).
T[Proof] = 1 years T[Proof] = 11 years
PFDavg = 8.72E-04 Valid for SIL 2 PFDavg = 9.60E-03 Valid for SIL 1
PFDavg vs T[Proof] table, with determination of SIL supposing module contributes 20% of entire safety function:
PFDavg vs T[Proof] table, with determination of SIL supposing module contributes 10% of entire safety function:
T[Proof] = 2 years T[Proof] = 20 years
PFDavg = 1.74E-03 Valid for SIL 2 PFDavg = 1.74E-02 Valid for SIL 1
Systematic capability SIL 3.
L
N
L
N
-+
...
-+-+-+
FLT
AC
AC1
DC ND Output Load
+
PSM1250
Module Position
number 1
LCD
touch screen
color dislpay
PSO1250
-
AC2
FLT
AC
FLT
AC
FLT
AC
PSM1250
Module Position
number 2
PSM1250
Module Position
number 5
PSM1250
Module Position
number 6
Fault 2+6
Fault 1+5
AC2
AC1
Safety
PLC
input Safety
PLC
input
COM FLT Modbus
48 Vdc, 50A (+ 50A redundancy)
1st Group
1st and 2nd modules 2nd Group
5th and 6th modules

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
10
Functional Safety Manual and Application
3) Application without HS capability and NE output load
L
N
L
N
-+
...
-+-+-+
FLT
AC
AC1
DC NE Output Load
+
PSM1250
Module Position
number 1
LCD
touch screen
color dislpay
PSO1250
-
AC2
FLT
AC
FLT
AC
FLT
AC
PSM1250
Module Position
number 2
PSM1250
Module Position
number 5
PSM1250
Module Position
number 6
Fault 2+6
Fault 1+5
AC2
AC1
Safety
PLC
input Safety
PLC
input
COM FLT Modbus
48 Vdc, 50A (+ 50A redundancy)
Failure category Failure rates (FIT)
λdd = Total Dangerous Detected failures 11.70
λdu = Total Dangerous Undetected failures 5.66
λsd = Total Safe Detected failures 0.00
λsu = Total Safe Undetected failures 163.52
λtot safe = Total Failure Rate (Safety Function) = λdd + λdu + λsd + λsu 180.88
MTBF (safety function) = (1 / λtot safe) + MTTR (8 hours) 631 years
λno effect = “No Effect” failures 10331.96
λnot part = “Not Part” failures 679.56
λtot device = Total Failure Rate (Device) = λtot safe + λno effect + λnot part 11192.40
MTBF (device) = (1 / λtot device) + MTTR (8 hours) 10 years
PFDavg (TI = 1 year) = λdu * (0.5*8760 + 8)h + λdd * 8h 2.493E-05
λsd λsu λdd λdu SFF DCD
0.00 FIT 163.52 FIT 11.70 FIT 5.66 FIT 96.87% 67.40%
Failure rates table according to IEC 61508:2010 :
Failure rate table:
Safety Function and Failure behavior: PSS1250 without HS and 2+2 PSM1250 modules is considered to be operating in Low Demand mode, as a Type A module, having Hardware
Fault Tolerance (HFT) = 1 or redundant configuration 1+1 on input/output. Its failure behaviour for NE output load is described by the following definitions:
□Fail-Safe State: it is defined as the system output going below 4 Vdc. Internal diagnostics detect and notify Low/High (Under/Over voltage) fails (DD) to logic solver, which can
operate to convert these fails to the fail-safe state, requiring to turn off all malfunctioning power supplies and to replace them with new PSM1250 modules.
□Fail Safe: failure mode that causes the system to go to the defined fail-safe state without a demand from the process.
□Fail Dangerous: failure mode that does not respond to a demand from the process (i.e. being unable to go to the defined fail-safe state), so that the system output voltage is
blocked or oscillating between 4 and 40 Vdc or above 60 Vdc, and both internal diagnostics cannot detect and notify faults to logic solver.
□Fail High - Overvoltage: failure mode that causes the system output to go above 60 Vdc. Internal overvoltage protections try to limit system output voltage < 60 Vdc,
otherwise internal crowbars trip to fail safe state for system output ≥60 Vdc. Internal diagnostics detect and notify High fail to logic solver, which does not automatically trip on
this failure, classified as Dangerous Detected (DD).
□Fail Low - Undervoltage: failure mode that causes the system output to go between 4 and 40 Vdc. Internal diagnostics detect and notify Low fail to logic solver, which does not
automatically trip on this failure, classified as Dangerous Detected (DD).
□Fail “No Effect”: failure mode of a component that plays a part in implementing the safety function but that is neither a safe failure nor a dangerous failure, so that the system
output voltage is deviated between 40 and 60 Vdc. When calculating the SFF, this failure mode is not taken into account.
□Fail “Not part”: failure mode of a component that is not part of the safety function but part of the circuit diagram and is listed for completeness. When calculating the SFF, this
failure mode is not taken into account.
The PSO1250 diagnostic module does not interfere with power system functional safety. The power system can perfectly work without diagnostic module and any failure of the
PSO1250 diagnostic module does not affect system performance, reliability and SIL level of this Functional Safety application. Failure rate data are from Siemens Standard SN29500.
Description: In normal operation 2+2 PSM1250 modules are powered by connecting AC1 input supply to two modules and AC2 input supply to other ones by means of related terminal
blocks on the Back Panel PCB (see previous functional diagram for more information). The 1st and 5th PSM1250 fault relay contacts must be connected in series to Safety PLC or Safe-
ty logic solver. The 2nd and 6th PSM1250 fault relay contacts must be connected in series to Safety PLC or Safety logic solver. Each power supply internal diagnostic uses this contact
to notifies under/over voltage module faults to logic solver, which can require to turn off this power supply and to replace it with a new PSM1250 module.
In absence of module fault the relay contact is closed, while in presence of module fault the relay contact is open. Green Power ON LED of each PSM1250 is lit with AC input presence
The outputs of the 1st and 2nd PSM1250 modules are already paralleled on the Back Panel PCB by specific copper bars, in order to give the 1st Group output.
The outputs of the 5th and 6th PSM1250 modules are already paralleled on the Back Panel PCB by specific copper bars, in order to give the 2nd Group output.
The positive (+) pole of the 1st Group output is already connected (by specific copper bar on the Back Panel PCB) to the negative (-) pole of the 2nd Group output, in order to connect in
series two groups and to get 48 Vdc output. Therefore, the NE output load is connected (by related output copper bars with screw terminals on the Back Panel PCB) between
the negative (-) pole of the 1st Group output and the positive (+) pole of the 2nd Group output, that is 48 Vdc power system output.
In normal condition, NE output load is Normally Energized (NE). In absence of one only AC input supply (AC1 or AC2), two PSM1250 modules are shutdown (their fault relay contacts
are open) but the other ones operate in normal condition, so that output load is normally energized.
In absence of both AC input supplies (AC1 and AC2), 2+2 PSM1250 modules are shutdown (their fault relay contacts are open) and output load is de-energized (Safe State).
T[Proof] = 4 years T[Proof] = 20 years
PFDavg = 9.97E-05 Valid for SIL 3 PFDavg = 4.99E-04 Valid for SIL 2
PFDavg vs T[Proof] table, with determination of SIL supposing module contributes 20% of entire safety function:
PFDavg vs T[Proof] table, with determination of SIL supposing module contributes 10% of entire safety function:
T[Proof] = 8 years T[Proof] = 20 years
PFDavg = 1.99E-04 Valid for SIL 3 PFDavg = 4.99E-04 Valid for SIL 2
Systematic capability SIL 3.
1st Group
1st and 2nd modules 2nd Group
5th and 6th modules

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 AG.M. International ISM0528-1 11
Functional Safety Manual and Application
4) Application without HS capability and ND output load
L
N
L
N
-+
...
-+-+-+
FLT
AC
AC1
DC ND Output Load
+
PSM1250
Module Position
number 1
LCD
touch screen
color dislpay
PSO1250
-
AC2
FLT
AC
FLT
AC
FLT
AC
PSM1250
Module Position
number 2
PSM1250
Module Position
number 5
PSM1250
Module Position
number 6
Fault 2+6
Fault 1+5
AC2
AC1
Safety
PLC
input Safety
PLC
input
COM FLT Modbus
48 Vdc, 50A (+ 50A redundancy)
1st Group
1st and 2nd modules 2nd Group
5th and 6th modules
Failure category Failure rates (FIT)
λdd = Total Dangerous Detected failures 7.64
λdu = Total Dangerous Undetected failures 173.24
λsd = Total Safe Detected failures 0.00
λsu = Total Safe Undetected failures 10331.96
λtot safe = Total Failure Rate (Safety Function) = λdd + λdu + λsd + λsu 10512.84
MTBF (safety function) = (1 / λtot safe) + MTTR (8 hours) 11 years
λnot part = “Not Part” failures 679.56
λtot device = Total Failure Rate (Device) = λtot safe + λno effect + λnot part 11192.40
MTBF (device) = (1 / λtot device) + MTTR (8 hours) 10 years
PFDavg (TI = 1 year) = λdu * (0.5*8760 + 8)h + λdd * 8h 7.60E-04
λsd λsu λdd λdu SFF DCD
0.00 FIT 10331.96 FIT 7.64 FIT 173.24 FIT 98.35% 4.22%
Failure rates table according to IEC 61508:2010 :
Failure rate table:
Safety Function and Failure behavior: PSS1250 without HS and 2+2 PSM1250 modules is considered to be operating in Low Demand mode, as a Type A module, having Hardware
Fault Tolerance (HFT) = 1 or redundant configuration 1+1 on input/output. Its failure behaviour for ND output load is described by the following definitions:
□Fail-Safe State: it is defined as the system output going between 40 and 60 Vdc. Internal diagnostics detect and notify High (Over voltage) fails (DD) to logic solver, which can
operate to convert these fails to the fail-safe state, requiring to turn off malfunctioning power supply and to replace it with new PSM1250 module.
□Fail Safe: failure mode that causes the system to go to the defined fail-safe state without a demand from the process.
□Fail Dangerous: failure mode that does not respond to a demand from the process (i.e. being unable to go to the defined fail-safe state), so that the system output voltage is
blocked or oscillating between 0 and 40 Vdc or above 60 Vdc, and internal diagnostic cannot detect and notify faults to logic solver.
□Fail High - Overvoltage: failure mode that causes the system output to go above 60 Vdc. Internal overvoltage protection tries to limit output voltage < 60 Vdc, otherwise
for output ≥60 Vdc internal crowbars trip, turning off malfunctioning power supply. Internal diagnostics detect and notify High fail to logic solver, which does not automatically trip
on this failure, classified as Dangerous Detected (DD).
□Fail Low - Undervoltage: failure mode that causes the system output to go between 0 and 40 Vdc. This failure mode is dangerous, but internal diagnostic notifies Low fail to
logic solver, which cannot convert this failure to the fail-safe state but it can only require to turn off malfunctioning power supply and to replace it with a new PSM1250 module.
□Fail “Not part”: failure mode of a component that is not part of the safety function but part of the circuit diagram and is listed for completeness. When calculating the SFF, this
failure mode is not taken into account.
The PSO1250 diagnostic module does not interfere with power system functional safety. The power system can perfectly work without diagnostic module and any failure of the
PSO1250 diagnostic module does not affect system performance, reliability and SIL level of this Functional Safety application. Failure rate data are from Siemens Standard SN29500.
Description: In normal operation 2+2 PSM1250 modules are powered by connecting AC1 input supply to two modules and AC2 input supply to other ones by means of related terminal
blocks on the Back Panel PCB (see previous functional diagram for more information). The 1st and 5th PSM1250 fault relay contacts must be connected in series to Safety PLC or Safe-
ty logic solver. The 2nd and 6th PSM1250 fault relay contacts must be connected in series to Safety PLC or Safety logic solver. Each power supply internal diagnostic uses this contact
to notifies under/over voltage module faults to logic solver, which can require to turn off this power supply and to replace it with a new PSM1250 module.
In absence of module fault the relay contact is closed, while in presence of module fault the relay contact is open. Green Power ON LED of each PSM1250 is lit with AC input presence
The outputs of the 1st and 2nd PSM1250 modules are already paralleled on the Back Panel PCB by specific copper bars, in order to give the 1st Group output.
The outputs of the 5th and 6th PSM1250 modules are already paralleled on the Back Panel PCB by specific copper bars, in order to give the 2nd Group output.
The positive (+) pole of the 1st Group output is already connected (by specific copper bar on the Back Panel PCB) to the negative (-) pole of the 2nd Group output, in order to connect in
series two groups and to get 48 Vdc output. Therefore, the ND output load is connected (by related output copper bars with screw terminals on the Back Panel PCB) between
the negative (-) pole of the 1st Group output and the positive (+) pole of the 2nd Group output, that is 48 Vdc power system output. In normal condition, absence of both AC input
supplies (AC1 and AC2) implies that 2+2 PSM1250 modules are shutdown (their fault relay contacts are open) and output load is Normally De-energized (ND). In presence of one only
AC input supply (AC1 or AC2), two PSM1250 modules are shutdown (their fault relay contacts are open) but the other ones are correctly turned on, so that output load is energized (Safe
State). In presence of both AC input supplies (AC1 and AC2), 2+2 PSM1250 modules are correctly turned on and output load is energized (Safe State).
T[Proof] = 1 years T[Proof] = 13 years
PFDavg = 7.60E-04 Valid for SIL 2 PFDavg = 9.88E-03 Valid for SIL 1
PFDavg vs T[Proof] table, with determination of SIL supposing module contributes 20% of entire safety function:
PFDavg vs T[Proof] table, with determination of SIL supposing module contributes 10% of entire safety function:
T[Proof] = 2 years T[Proof] = 20 years
PFDavg = 1.52E-03 Valid for SIL 2 PFDavg = 1.52E-02 Valid for SIL 1
Systematic capability SIL 3.

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
12
According to IEC 61508-2, the proof test will be performed to reveal dangerous faults which cannot be otherwise detected. This means that it is necessary to specify how dangerous
undetected faults, which have been noted during the FMEDA analysis, can be revealed during the proof test.
For Functional Safety applications with NE output load, the following Proof Test must be executed for each PSM1250 composing the Functional Safety used application.
It consists of the following steps:
Testing procedure at T-proof
Steps Action
1In order to control correct operating of the fault contact (FLT), necessary to give information about dangerous failures, take appropriate action on the safety-related PLC to
acquire presence of fault but to not take any action because fault condition is intentionally provoked.
2Shutdown the tested power supply module by unplugging: at least one of two top screws that fix PSM1250 into PSS1250 rack with HS capability; two top and two bottom screws
that fix PSM1250 into PSS1250 rack without HS capability and disconnecting the module from the rack unit. This action does not affect output load operating, which holds
normally energized because of fully redundant configuration on input (two independent AC lines) and output (paralleling connection for each group implies high availability) of
the Functional Safety application. The power supply module turn off time lasts some seconds (typically 5 to 10 sec). During this time, the power supply module output voltage
goes below 19.5 Vdc (undervoltage UV condition), therefore the fault relay contact must be open and the green Power ON LED must blink. The safety-related PLC must acquire
presence of fault, which proves that power supply internal diagnostic operates correctly. If the safety-related PLC does not acquire any fault, this means that fault relay contact is
blocked in closed position (for welding) or power supply internal diagnostic is wrongly operating. Therefore this power supply module must be replaced with new one.
3Turn on the tested power supply module by plugging: both two top screws that fix PSM1250 into PSS1250 rack with HS capability; two top and two bottom screws that fix
PSM1250 into PSS1250 rack without HS capability and connecting the module into the rack unit. After about 3 seconds the power supply module operates correctly in current
sharing mode with other paralleled power supply module of its group. This can be seen on the TFT display of PSO1250 overview module.
7 Plug two M6 nylon-capped lock nuts, to fix IP20 polycarbonate cover on the DC (+ / -) couple screw output terminals of the tested power supply module.
6Use an AC true rms voltmeter and connect its probes to DC (+ / -) couple screw output terminals in order to measure AC rms voltage. In normal operation conditions, the output
supply voltage should have no AC component, that is its rms value should be ideally null. But little ripple is allowed, therefore this value must be about 100 mVrms. If higher rms
value (as some volts) is measured, a dangerous failure which has produced an oscillation of the output voltage regulator is detected. Therefore this power supply module must
be replaced with new one.
5 Unplug two M6 nylon-capped lock nuts, to unfix IP20 polycarbonate cover from the DC (+ / -) couple screw output terminals of the tested power supply module.
4 Restore normal operation of the safety-related PLC, so that it can take any action if fault is acquired.
This test reveals 90% of all possible Dangerous Undetected failures in the PSM1250 power supply module and therefore in the PSS1250 system, when the output load is NE type.
Installation Procedure - 1st step: Back Panel installation for PSS1250-xx-7-48-D-W (wall mounting into a cabinet)
The following drawing with overall dimensions (mm) is only applicable to types: PSS1250-HS-7-48-D-W and PSS1250-7-48-D-W.
The back panel is fixed to a vertical wall into a cabinet by means of four screws through four 7.00 mm diameter holes shown in the drawing.
The back panel must only be installed as oriented in the following drawing. On the back panel is fixed the back panel PCB by means of six screws.
UP
RIGHT
LEFT
BOTTOM
1
Fig. 1 shows PSS1250-HS-7-48-D-W system (wall mounting into a cabinet), which includes the
following parts:
Back Panel and its PCB with connections for power and diagnostic modules and hot swapping
control circuits;
19” Rack unit, enclosure with guides for inserting modules and microswitches board connected
(by flat cable) to the hot swapping control circuits on Back Panel PCB;
4 Power Supply Modules (PSM1250), for each inserting position (Pos.1, Pos.2, Pos.5, Pos.6).
The Pos.3 and Pos.4 cannot be used because they are not connected to AC input & DC output.
Diagnostic module in Pos.7 (PSO1250) with TFT LCD touch color screen for diagnostic
information about each power module.
This Fig.1 can be also used for PSS1250-HS-7-48-D-F system (frontal rack mounting into a cabinet)
because this system differs to the previous one only for the rack unit
mechanical structure and not for the connections between components:
Instead, the PSS1250-7-48-D-W or F system (without HS capability) differs to Fig.1 system only for
the absence of microswitches board, related flat cable and hot swapping control circuits on Back
Panel PCB.
2
3
4
1 2 3 4
System composition
1
2
2
2
3
4
Fig. 1

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 AG.M. International ISM0528-1 13
Installation Procedure - 2nd step: Wiring of AC input lines, faults and modbus terminal blocks on Back Panel PCB of PSS1250-xx-7-48-D
The following picture shows for example the terminal block wiring of PSS1250-HS-7-48-D Back Panel PCB.
For PSS1250-7-48-D Back Panel PCB, the terminal block wiring is the same.
Fault 1 Fault 2 Fault 5 Fault 6 Common Fault &
Modbus Diagnostic
AC1 AC1 AC1AC2 AC2 AC2
The PSS1250(-HS)-7-48-D redundant system requires to use two AC input power lines (AC1 and AC2) with different lines and neutrals but the same Earth Ground connection,
in order to guarantee fully redundant configuration from the input to the output of power system.
Each PSM1250 unit slot (only 1st, 2nd, 5th and 6th, because 3rd and 4th cannot be used) must receive AC mains by means of a circuit breaker or switch with the following features:
B or C characteristic 20 Amps when nominal low input voltage 110÷120 Vac (±10%) is used;
B or C characteristic 10 Amps when nominal high input voltage 220÷240 Vac (±10%) is used.
Connect AC1 input power line to input terminal blocks of positions N.1, 5 (odd positions) and connect AC2 input power line to input terminal blocks of positions N.2, 6 (even positions).
See functional diagrams at page 7 for more information about wiring connection.
The last position on the right is used for PSO1250 diagnostic module, connect both AC1 and AC2 input power lines to related terminal blocks in order to guarantee continuous
operation of diagnostic module even after shutdown of one AC input line. The PSO1250 unit slot must receive AC1 and AC2 mains by means of a circuit breaker or switch with
the following features: B or C characteristic 0.5 Amps when input voltage nominal range 110÷240 Vac (±10%) is used.
For AC input terminal blocks, use a cable section range from 14AWG (or 2 mm2) to 11AWG (or 4 mm2) and tighten terminal block screws with maximum 0.6 Nm torque.
For fault contact output (of each PSM1250 or common of PSO1250) and Modbus terminal blocks, use a cable section range from 20AWG (or 0.5 mm2) to 16AWG (or 1.5 mm2) and
tighten terminal block screws with maximum 0.25 Nm torque. For more information about Fault connection, please see Functional Safety applications on pages 8 to 11.
AC line internal fuses are not user replaceable. The unit cannot be repaired by the end user and must be returned to the manufacturer or his authorized representative.
Line Neutral
Earth
Ground
1st
pos.
2nd
pos.
5th
pos.
6th
pos.
7th
pos.

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
14
Installation Procedure - 3rd step: Rack unit installation on Back Plane for PSS1250-xx-7-48-D-W (wall mounting into a cabinet)
Tighten nuts and
groovers on the
Wall Mounting
Panel bolts
Tighten nuts and
groovers on the
Wall Mounting
Panel bolts
The following drawing shows overall dimensions (mm) of PSS1250-xx-7-48-D-W, with Rack unit mounted on related Back Plane with its PCB.
Fix the Rack unit to 6 wall mounting panel bolts (3 on the right side and 3 on the left side) by means of 6 M6 nuts and groovers.
Top view
Front view
Side view
Not cover up-side and down-side
input flows of air zones
Not cover front side
output flows of air zones

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 AG.M. International ISM0528-1 15
Installation Procedure - 3rd step: Installation of PSS1250-xx-7-48-D-F (frontal rack mounting into a cabinet)
The following drawing shows overall dimensions (mm) of PSS1250-xx-7-48-D-F, where Rack unit and Back Plane with its PCB are already fixed together.
Fix the PSS1250 to the rack rails of a cabinet, as frontal rack mounting, matching 4 holes of Rack unit lugs (2 on the right side lug and 2 on the left side lug) with rail holes and
fixing with 4 screws and related nuts. In addition, on the left and right rack sides, use a cabinet anchoring bar or bracket to hold up the rack unit.
Front view
Side view
Top view
On the left side, use a cabinet
anchoring bar or bracket
to hold up the rack unit.
On the right side,
use a cabinet anchoring bar or
bracket to hold up the rack unit.
Not cover up-side and down-side
input flows of air zones
Not cover front side
output flows of air zones

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
16
Installation Procedure - 4th step (for models with HS) - Section A: Installation of flat cable between microswitches PCB and
Back Panel PCB for Hot Swapping control
Fig. 3 shows PSS1250-HS-7-48-D Back Panel PCB with a 12 poles male connector, which must be connected with the flat cable coming from the microswitches PCB of the Rack unit.
In the Fig. 2-3-4-5 is shown how to connect this flat cable for PSS1250-HS-7-48-D system.
During installation of the PSS1250-HS-7-48-D, connect the flat cable, coming from the microswitches PCB of the Rack unit, to the 12 poles male connector on Back Panel PCB, as
shown in Fig. 4-5.
Fig. 2 Fig. 3
Fig. 4 Fig. 5

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 AG.M. International ISM0528-1 17
Installation Procedure - 4th step (for models with HS) - Section B: Installation and start up of PSO1250 Diagnostic Module
Insert the PSO1250 diagnostic module in the last position (7th) on the right of the Rack unit and fix the module to the Rack unit by means of its 4 screws on its front side.
Front side of PSO1250 with
its 4 screws to fix it to the
rack unit.
Independently from installation or not of the PSO1250 module, power AC1 and AC2 input power lines anyway.
Each Hot Swapping Control (HSC) circuit (one for each PSM1250 position) is supplied from AC1 or AC2 input line.
The Hot Swapping Control circuit controls if PSM1250 can be installed and fixed to the Rack unit.
If no PSM1250 module is installed and fixed into the Rack unit, no Hot Swapping Control circuit can give input power lines to the Back Panel PCB female connector.
In this condition, each red LED must be OFF.
If a red LED is ON, it means that related Hot Swapping Control circuit is not correctly operating and therefore no PSM1250 module shall be insert and fixed into its Rack
position.
PSM1250 module can be installed and fixed into the Rack unit only if corresponding Back Panel PCB red LED is OFF.
Normal condition: the red LED is OFF.
The PSM1250 module can be installed and fixed into the
Rack unit position.
Dangerous condition: the red LED is ON.
The PSM1250 module must not be installed.
Back Panel PCB
female connector
to connect
PSM1250 module
Back Panel PCB
female connector
to connect
PSM1250 module
Red LED is OFF Red LED is ON
After installation of the PSO1250 module, power AC1 and AC2 input power lines in order to turn on diagnostic module.
For more information about diagnostic module features and its set up, please see description from page 26.
Installation Procedure - 4th step (for models with HS) - Section C: HSC red LED signalling test
For example is only shown
a PSS1250-HS-7-48-D-W
system, for wall mounting
into a cabinet.

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
18
Installation Procedure - 4th step (for models with HS) - Section D: Installation and pre-start up of PSM1250 Power Supply Module
...then tighten 2 top screws
AC1 and AC2 input power lines are powered. Therefore PSM1250 module can be installed and fixed into the Rack unit only if corresponding back panel red LED is OFF.
The following procedure is split in 3 sub-steps and it is the same for each PSM1250, independently from its position in the Rack unit.
Starting from position 1 to position 6 (excluding position 3 and 4 because cannot be used), execute pre-start up of each PSM1250 module.
1st sub-step: insert and fix the PSM1250 module into the Rack unit by means of its 4 screws on its front side. Two of them in the bottom part are only used for mechanical purpose;
the other two, in the top part, when completely tightened, close the microswitches and enable the hot swap control circuit to provide input power lines to PSM1250 module
by Back Panel PCB female connector. First of all, tighten 2 bottom screws and then tighten 2 top ones.
First tighten 2 bottom screws...
2nd sub-step: with PSM1250 module powered, its front panel Power ON green LED is ON and 24 Vdc (factory setting)
output voltage is present on PSM1250 screw output terminals DC- and DC+ (see page 6 for more information
about Power ON green LED signalling). The output voltage can be measured on PSM1250 screw output
terminals by means of a multimeter. In addition, on the TFT color screen of PSO1250 diagnostic module it is
possible to monitor the PSM1250 module status and to collect information about the power supply: for example
output voltage value (see description from page 26).
If it is required to set an output voltage value different from factory setting (24 Vdc), use the trimmer for output
voltage adjusting. Turn the trimmer clockwise (to the right) to increase output voltage (max. 28 Vdc) or turn the
trimmer counterclockwise (to the left) to decrease output voltage (min. 21 Vdc).
To set PSS1250-HS-7-48-D output voltage to V_out-system value in the range 42 to 56 Vdc, then V_out-PSM
must be set to V_out-system / 2 value, because two groups have their outputs connected in series and each
group is composed by 2 PSM1250 with paralleled outputs and with load sharing circuits. Warning: for correct
current sharing operation in a group, power supply modules of a group must have output voltages calibrated
within ± 0.5 V.
Trimmer for output voltage adjusting
(use a little cross head isolated
screwdriver)
Power ON
green LED
3rd sub-step: after having adjusted PSM1250 output voltage, shut down the power module unplugging the 2 top screws in order to repeat sub-steps 1 to 3 procedure for other
modules and complete the setting for all PSM1250 of PSS1250 power system.
Unplug the 2 top screws.
Green LED is OFF.
For example is only shown
a PSS1250-HS-7-48-D-W
system, for wall mounting
into a cabinet.
This step could be not executed if PSS1250-HS-7-48-D output voltage factory setting to 48 Vdc is corrected for your applications.
Instead, execute this step if it’s necessary to set up a different value for PSS1250-HS-7-48-D output voltage in the range 42 to 56 Vdc.
1st PSM1250 screw output terminals
on copper bars:
DC1- is its negative out pole,
DC1+ is its positive out pole.
2nd PSM1250 screw output terminals
on copper bars:
DC2- is its negative out pole,
DC2+ is its positive out pole.
DC1- and DC2- are also
negative out poles of
of PSS1250-HS-7-48-D.
5th PSM1250 screw output terminals
on copper bars:
DC5- is its negative out pole,
DC5+ is its positive out pole.
6th PSM1250 screw output terminals
on copper bars:
DC6- is its negative out pole,
DC6+ is its positive out pole.
DC5+ and DC6+ are also
positive out poles of
of PSS1250-HS-7-48-D.
In this figure only the 1st PSM1250 module is
shown but the same disconnection procedure is
also applicable to other PSM1250 modules.

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 AG.M. International ISM0528-1 19
At this step, PSO1250 diagnostic module is installed and fixed to rack unit with 4 screws, while each PSM1250 power module is installed and fixed to rack unit with 2 bottom screws
only (2 top screws are unplugged to keep PSM1250 shutdown).
Unpower AC1 and AC2 input power lines (also PSO1250 will turn off) before starting the wiring of bottom screw output terminals on copper bars (DC output lines) of Back Panel PCB.
To wire negative DC output lines (DC1- and DC2- screw output terminals) of PSS1250 system, see Fig. 6-7-8-9-10.
See functional diagrams on pages 7 for more information about wiring connection.
Installation Procedure - 4th step (for models with HS) - Section E: Wiring of 1st & 2nd PSM1250 screw output terminals on copper bars
of Back Panel PCB (PSS1250-HS negative DC out lines)
For DC screw output terminals, use a cable section range from 6AWG (or 13 mm2) to 5AWG (or 16 mm2) and tighten M6 nut+groover+washer on screw with maximum 4 Nm torque.
Fig. 6
washer
groover
nut
Unplug M6 nut, groover and washer.
Then insert the cable lug (at least 6.5 mm hole diameter)
with wire (negative out wire of PSS1250 system), washer
and groover on the screw output terminal.
Finally tighten nut to fix wire. Fig. 8
A polycarbonate cover is used for IP20 to protect each
couple of screw output terminals. Break only left side
preformed blanking element to allow cable passage
(negative out wire of PSS1250 system). Do NOT break
right side preformed blanking element. Then insert and
fix the cover on screw output terminal by means of M6
nylon-capped lock nut.
Fig. 9
Break this
blanking
element
nut
NOT Break
this blanking
element
Fig. 10
Fig. 7

PSS1250(-HS)-7-48-D - SIL 3 Power Supply System, 48 Vdc, 50 A G.M. International ISM0528-1
20
Installation Procedure - 4th step (for models with HS) - Section F: Wiring of 5th & 6th PSM1250 screw output terminals on copper bars of
Back Panel PCB (PSS1250-HS positive DC out lines) & PSS start-up
At this step, AC1 and AC2 input power lines are unpowered, PSO1250 diagnostic module is installed and fixed to rack unit with 4 screws, while each PSM1250 power module is
installed and fixed to rack unit with 2 bottom screws only (2 top screws are unplugged to keep PSM1250 shutdown).
To wire positive DC output lines (DC5+ and DC6+ screw output terminals) of PSS1250 system, see Fig. 11-12-13-14-15. See functional diagrams on pages 7 about wiring connection.
For DC screw output terminals, use a cable section range from 6AWG (or 13 mm2) to 5AWG (or 16 mm2) and tighten M6 nut+groover+washer on screw with maximum 4 Nm torque.
Fig. 11
washer
groover
nut
Unplug M6 nut, groover and washer.
Then insert the cable lug (at least 6.5 mm hole diameter)
with wire (positive out wire of PSS1250 system), washer
and groover on the screw output terminal.
Finally tighten nut to fix wire. Fig.13
A polycarbonate cover is used for IP20 to protect each
couple of screw output terminals. Break only right side
preformed blanking element to allow cable passage
(positive out wire of PSS1250 system). Do NOT break
left side preformed blanking element. Then insert and
fix the cover on screw output terminal by means of M6
nylon-capped lock nut.
Fig. 15
Fig. 12
Break this
blanking
element
nut
NOT Break
this blanking
element
Fig. 14
After having wired all DC output lines, starting from position 1 to position 6 (excluding position 3 and 4 because cannot be
used), tighten 2 top screws of each PSM1250 as shown in Fig. 16.
Tighten 2 top screws
Fig. 16
Now power AC1 and AC2 input power lines.
PSO1250 diagnostic module (if it’s present) and each PSM1250 power module turn on and the PSS1250-HS-7-48-D system DC output lines will power the load.