Bender RCMA126P1-S User manual

Power in electrical safety
Operating Manual
RCMA126P1-S
AC/DC sensitive
residual current monitoring module
for installation into photovoltaic converters
Software version 9
TGH1423en/04.2010

©Dipl.-Ing. W. Bender GmbH & Co. KG
All rights reserved.
Reprinting only with permission
of the publisher.
Subject to change!
Dipl.-Ing. W. Bender GmbH & Co. KG
Londorfer Str. 65 • 35305 Grünberg • Germany
Postfach 1161 • 35301 Grünberg • Germany
Tel.: [phone]
Fax: [phone]
E-mail: [email protected]
Web: http://www.bender-de.com

3
Table of Contents
TGH1423en/04.2010
1. Effective use of this manual .................................................................................. 5
1.1 Notes for the user ..................................................................................................................... 5
2. Safety information .................................................................................................. 7
2.1 General safety information ...................................................................................................7
2.2 Work activities on electrical installations ........................................................................ 7
3. Function ....................................................................................................................9
3.1 Product description ................................................................................................................. 9
3.2 Function ...................................................................................................................................... 9
3.3 Measurement technique: ...................................................................................................... 9
4. Installation, connection ...................................................................................... 11
4.1 Connection assignment ..................................................................................................... 11
5. Operation and setting ......................................................................................... 13
5.1 PWM measured value output X1 ..................................................................................... 13
5.2 Interface protocol ................................................................................................................. 13
5.2.1 SPI timing ................................................................................................................................. 14
5.2.1.1 Timing for the receipt of one byte from the master .......................................... 14
5.2.1.2 Timing for the communication cycle from the Master ..................................... 14
5.2.2 Messages .................................................................................................................................. 15
5.2.2.1 RESET .................................................................................................................................. 15
5.2.2.2 Selecting the measuring range ................................................................................. 15
5.2.2.3 Hardware version query .............................................................................................. 16
5.2.2.4 Software version query ................................................................................................ 16
5.2.2.5 Status query ..................................................................................................................... 16
5.2.2.6 Function control ............................................................................................................. 17
5.2.2.7 Reading slave data ......................................................................................................... 17
5.3 Other hardware features .................................................................................................... 17
5.4 Other software features ......................................................................................................18
5.5 Measuring range and measuring times ........................................................................ 18
5.5.1 Measuring range 30 mA, 100 mA .................................................................................... 18

Table of Contents
4TGH1423en/04.2010
5.5.2 Measuring times .................................................................................................................... 18
6. Technical data ....................................................................................................... 19
6.1 Data in tabular form .............................................................................................................. 19
6.2 Ordering information ........................................................................................................... 20
6.3 Dimension diagrams ............................................................................................................ 21

5
TGH1423en/04.2010
1. Effective use of this manual
1.1 Notes for the user
This manual is intended for electrically skilled persons in electrical engineering and electronics!
In order to make it easier for you to find specific text passages or references in this manual
and for reasons of comprehensibility, important information is emphasised by symbols. The
meaning of these symbols is explained below:
Information calling attention to hazards are marked with this warning symbol.
Information intended to assist the user to make optimum use of the product are
marked with the Info symbol.

Effective use of this manual
6TGH1423en/04.2010

7
TGH1423en/04.2010
2. Safety information
2.1 General safety information
In addition to this data sheet, the documentation of the device includes a sheet entitled "Im-
portant safety instructions for Bender products“.
2.2 Work activities on electrical installations
zAll work activities necessary for installation, commissioning or work activities during operation
of electrical devices or systems are to be carried out by adequately skilled personnel.
zObserve the relevant regulations applying to work on electrical installations, in particular DIN
EN 50110 or its subsequent regulations.
Unprofessional work activities on electrical installations may result in a threat of danger to
life and limb!
zIf the equipment is used outside the Federal Republic of Germany, the respective national
standards and regulations are to be observed. The European standard EN 50110
is recommended to be used as a directive.

Safety information
8TGH1423en/04.2010

9
TGH1423en/04.2010
3. Function
3.1 Product description
The AC/DC sensitive residual current monitoring module RCMA126P1-S is suitable for fault
current monitoring in transformerless photovoltaic inverters where direct and/or alternating
fault currents are likely to occur the value of which is constantly greater than zero.
3.2 Function
Residual current monitoring is carried out using an internal measuring current transformer.
The r.m.s. value is calculated by summing up the DC components included in the residual
current and the AC components that are below the cut-off frequency. A PWM signal in pro-
portion to the residual current is available at the module output (X1). If values are outside
the permissible measuring range, the signal will be available for 1 s after disconnection. The
PWM frequency is 8 kHz.
The measuring range 0…30/100 mA equates to 3…97 % PWM.
Measured values < 3 % and > 97 % signal that the residual current monitoring module is in-
active respectively defective. The residual current monitoring module is operated as a slave
on a SPI interface. The measuring range can be changed via the interface. In addition, the
software version and the statuses can be queried and a functional test can be carried out.
The monitoring module can be tested via the test winding at the module output (X11) using
an actual fault current (X11). For this purpose, a voltage of +3.3 V is applied at the connection
k of the test winding. Connection l of the test winding is connected to the module output
X11.
3.3 Measurement technique:
The residual current is measured using the magnetic saturation measurement principle. This
AC/DC sensitive method allows residual DC currents and residual AC currents to be detected.
The frequency range is 0...500 Hz.

Function
10 TGH1423en/04.2010

11
TGH1423en/04.2010
4. Installation, connection
4.1 Connection assignment
No. Plug designation Description
1X1 PWM (measured value output)
2X2 CS (ChipSelect interface)
3X3 SCK (CLOCK interface)
4X4 MISO (data output interface)
5X5 MOSI (data input interface)
6X6 U4 (voltage supply +3.3 V)
7X7 U2 (voltage supply +5 V)
8X8 AGND (ground)
9X9 U3 (voltage supply -5 V)
10 X10 (voltage supply +15 V)
11 X11 (test winding)
12 X12 (ground)
50
65
27,5
3,8
5,5 6,5 7,5
13
12
7
6
5
4
211
89
10

Installation, connection
12 TGH1423en/04.2010

13
TGH1423en/04.2010
5. Operation and setting
5.1 PWM measured value output X1
The measured residual current is available at the measurement output X1 as a PWM signal
in proportion to the residual current. Values outside the permissible measuring range are
available for approximately 1s after disconnection. The PWM frequency is 8 kHz.
Sensitivity of the device:
zMeasuring range 30 mA: M = 30 mA / 97 % = 0.3093 mA/% pulse width
0...30 mA equates to 0...97 %, where measured values < 3 % are output with 3 % PWM
zMeasuring range 100 mA: M = 100 mA / 97 % = 1.0309 mA/% pulse width
0...100 mA equates to 0...97 %, where measured values < 3 % are output with 3 % PWM.
Measured values smaller than 3 % are output with a 3 % pulse width.
A pulse width of > 97 % resp. < 3 % signals an inactive residual current monitoring module,
the start-up phase of the software or an error message.
5.2 Interface protocol
The residual current monitoring module is operated as a slave on an SPI interface. The slave
responds to a command by writing the associated answer to the send buffer. In response to
the command "Get slave data", the master then reads data from the slave. The answer read
from the slave is only valid for the master when the command "Get slave data" has been sent
before. A command consists of 1 byte.
The SPI interface is operated with the following parameters:
- Clock = 200 kHz, clock inactive LOW
- Data sample on clock's rising edge, data setup on clock's falling edge
- MSB first
- SlaveSelect (CS) LOW during transmission
A communication cycle consists of the following transmission sequence:
- Master is sending a command byte while SlaveSelect is LOW
- Master is waiting tpause1 while SlaveSelect is HIGH
- Master is sending the command “Get answer” while SlaveSelect is LOW
The next cycle will be repeated by the master after a waiting period of tpause2, at the earliest.

Operation and setting
14 TGH1423en/04.2010
5.2.1 SPI timing
5.2.1.1 Timing for the receipt of one byte from the master
tcs > 20ns
SPI signals:
SCK: Clock, generated by the master
MOSI: Data is sampled by slave
MISO: Data output from slave
CS: Slave-Select signal from master
5.2.1.2 Timing for the communication cycle from the Master
tpause1 ≥1.5 ms
tpause2 ≥200 ms
t
cs
MSB Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 LSB
SCK
MOSI
MISO
CS
(sampling)
SCK/MISO
MOSI
tpause1 tpause2
CS
Command
Command
Get answer
Get answer

Operation and setting
15
TGH1423en/04.2010
5.2.2 Messages
5.2.2.1 RESET
While resetting the residual current module, ensure that no residual current is flowing, since
the RCMA126P1-S carries out a self calibration during software start-up.
The reset procedure takes up to 2 seconds after the slave has checked that the supply voltage
+15V is not outside the tolerance.The device status can be queried during this period.
The RCMA status is "inactive“ for the duration of the reset procedure. During this time the
measuring range cannot be changed. The command also deletes the counter of the function
control. Therefore this command is not allowed during the reset procedure. The answer will
then always be 0x80.
Recommended command sequence under consideration of the timing:
- Send reset command
- Send status command until the message "RCMA active" is sent.
The response to this command will be written into "Answer" register. In this case "Answer"
from RCMA126P1-S means that the received value will be written into the SPI send register.
The master can get this answer byte by sending a dummy command (0x00h) to which the
RCMA126P1-S does not initiate an action. The value previously written into the send register
will then be clocked into the master.
5.2.2.2 Selecting the measuring range
Measuring range 100 mA:
0...100 mA equates to 0...97 %, where measured values < 3 % are output with 3 % PWM.
Measuring range 30 mA:
0...30 mA equates to 0...97 %, where measured values < 3 % are output with 3 % PWM.
After powering up, the residual current monitoring module always starts in the 100 mA meas-
uring range. A change of the measuring range will not be stored permanently.
Converter Command Send 0x80h
RCMA126 Answer 0x80h
Action Software reset and restart.
Initialisation and self calibration
Converter Command Send 0x88h: Measuring range 100 mA
Send 0x84h: Measuring range 30 mA
RCMA126 Answer
Measuring range 100 mA:
0x88h: RCMA active
0x89h: RCMA inactive
Measuring range 30 mA:
0x84h: RCMA active
0x85h: RCMA inactive
Action Setting the measuring range

Operation and setting
16 TGH1423en/04.2010
5.2.2.3 Hardware version query
5.2.2.4 Software version query
5.2.2.5 Status query
The device status and measuring range can be queried. During the start and initialisation
phase and in case of an error, the status is "inactive", i.e. Bit 0 = 0. In this case, the PWM duty
cycle is 1 %.
Meaning of the bits:
Bit 0: 1 = RCMA126P1-S active, the output measuring signal is valid
Bit 1: specifies the currently set measuring range
Bit 2: is 1 during the initialisation phase of the software and during the
cyclic self test of the RCMA126P1-S (approx. every 5 hours)
Bit 3: is 1 during an offset measurement (is carried out after powering up
and a reset command)
Bit 4: general error flag that will be set if:
- during an internal self test a microcontroller error has been detected
- the measurement oscillator does not oscillate in the required range
- the deviation recognised during the offset measurement is too big
Bits 2, 3 and 4 only provide additional information about the device status. The residual cur-
rent monitoring module will become active (Bit 0 = 1) as soon as a residual current measure-
ment can be carried out. A residual current exceeding the measuring range results in a duty
cycle of 97 %. In this case, the status will remain "active".
The status can be queried approx. 100 ms after powering up of the residual current monitor-
ing module, at the earliest (Enable of the SPI interface after the self test and before calibra-
tion).
Converter Command Send 0x81h
RCMA126 Answer
>= 0x01h
(will be incremented each time the hardware
is changed)
Converter Command Send 0x86h
RCMA126 Answer
>= 0x01h
(will be incremented each time the software
is changed)
Converter Command Send 0x83h
RCMA126 Answer
Coded bit by bit:
Bit 0: 0 = RCMA inactive,
1 = RCMA active
Bit 1: 0 = measuring range 100 mA,
1 = measuring range 30 m A
Bit 2: 1 = self test active
Bit 3: 1 = device calibration active
Bit 4: 1 = common fault alarm
Bit 5: unused
Bit 6: always 1
Bit 7: always 1

Operation and setting
17
TGH1423en/04.2010
5.2.2.6 Function control
For function control, the residual current monitoring module returns a value which is incre-
mented whenever a command is requested. The start value for a software restart and after a
reset command is 0x00h.
5.2.2.7 Reading slave data
This command enables the master to read in the contents of the slave register. In contrast to
all other commands, the send register will not be changed by the slave.
Synchronisation by the master also takes place.
5.3 Other hardware features
The accuracy of residual current measurement depends on the supply voltage U1 (+15 V).
For this reason, continuous supply voltage monitoring is required to check that the voltage
is U1 = 13.5 V. If the voltage falls below the required minimum voltage, residual current
measurement will be deactivated (status: RCMA inactive). Simultaneously, the measured val-
ue output will be set outside its area of validity (PWM output = 1 %).
The residual current transformer utilises a test winding with N = 20 windings. The test wind-
ing is connected to the X11 (T) connection. The end of the second winding is connected to
U4 = +3.3 V on the residual current monitoring module.
Converter Command Send 0x82h
RCMA126 Answer
>= 0x00h
The value returned will be incremented each
time a command is requested and will be
reset to 0x00h when 0xffh is exceeded.
Converter Command Send 0x00h
RCMA126 Answer no answer!

Operation and setting
18 TGH1423en/04.2010
5.4 Other software features
The microcontroller only becomes active if the minimum supply voltage U4 > 3.0 V will be
exceeded. Initially, the microcontroller carries out a self test of the hardware and software
of the residual current monitoring module. During the start-up phase, it must be ensured that
the supply voltage is U1 ≥13.9 V and that no residual current is flowing. Only when residual
current measurement is started, the device status will be set to "active".
5.5 Measuring range and measuring times
5.5.1 Measuring range 30 mA, 100 mA
By default, the measuring range is 0…100 mA.
The measuring range is set via the SPI interface.
5.5.2 Measuring times
The measuring time starts when the residual current occurs and ends when the pulse width
of the monitoring module is set in proportion to the residual current. The change in residual
current is the amount of increase based on a static value within the measuring range. In this
case, the measuring times can only be reached when the residual current rises rapidly.
Change in residual
current Measuring time Minimum output value after the measuring time has elapsed
30 mA ≤150 ms ≥30 mA
60 mA ≤100 ms ≥40 mA
150 mA ≤20 ms 100 mA (limit of measuring
range)
START
Functional test
Offset measurement
Residual current measur.
Condition: U4 > 3 V
Status: Device inactive
PWM output: 1 %
Condition: U1 >= 13.9V
Status: Device inactive
Condition: U1>13.5V
Status: Device active
PWM output: >=3%
max. 100ms
max. 2s

19
TGH1423en/04.2010
6. Technical data
6.1 Data in tabular form
Voltage supply
U1................................................................................................................................................................. +15 V (±5 %)
U2..................................................................................................................................................... +5 V (+12 % / -5 %)
U3.......................................................................................................................................................-5 V (+12 % / -5 %)
U4.................................................................................................................................................. +3.3 V (+10 % / -5 %)
Ripple max................................................................................................................................................................. 60 mV
Power consumption ............................................................................................................................................. ≤0.5 W
Measuring circuit
Operating characteristics acc. to IEC 60755.............................................................................................................. Type B
Frequency range .............................................................................................................................................. 0…500 Hz
Measuring range ......................................................................................................................................0…30 / 100 mA
Relative uncertainty ........................................................................................................................................... 0…-20%
Max. nominal current.............................................................................................................................50 A / 50…60 Hz
Outputs
PWM frequency........................................................................................................................................................... 8 kHz
Tolerance of the PWM frequency.............................................................................................................................. ±1 %
Sensitivity measured value output:
Measuring range 0…100 mA .................................................................................................................. 100 mA / 97 %
Measuring range 0…30 mA .......................................................................................................................30 mA / 97 %
Resolution of setting
100 mA range........................................................................................................................................................... 0.76 %
30 mA range............................................................................................................................................................. 0.76 %
Interface ........................................................................................................................................................................... SPI
Clock frequency .......................................................................................................................................................200 kHz
Specified time
Changes in residual current IΔ= 30 mA (output X1)....................................................................................... ≤150 ms
............................................................................ minimum output value after reaching the measuring time: ≥30 mA
Changes in residual current IΔ= 60 mA (output X1)........................................................................................ ≤100 ms
.............................................................................minimum output value after reaching the measuring time: ≥40 mA
Changes in residual current IΔ= 150 mA (output X1)....................................................................................... ≤20 ms
................................... minimum output value after reaching the measuring time: 100 mA (limit of measuring range)
Classification of mechanical conditions
Operating conditions in acc. with EN 60721-3-3................................................................................................Class 3M6
Shock resistance .................................................................................................................................................25 g / 6 ms
Vibration resistance....................................................................................................2…9 Hz / 7 mm, 9…200 Hz / 2 g
Environmental conditions
Climatic class acc. to IEC 60721-3-4 .......................................................................................................................... 4K4H
Ambient temperature, during operation...............................................................................................- 25 °C…+ 80 °C
Ambient temperature, during transport................................................................................................- 40 °C…+ 80 °C
Relative humidity .........................................................................................................10…90 %, 100 % max. 48 hours
Air pressure................................................................................................................................................... 70…106 kPa
Condensation, ice formation.............................................................................................................. possible temporarily

Technical data
20 TGH1423en/04.2010
Connection
Plug-in connectors for PCBs, single-row .......................................................................................... 0.65 mm x 0.65 mm
Modular dimensions ............................................................................................................................................ 2.54 mm
Other
Operating mode ............................................................................................................................... continuous operation
Position of normal use ....................................................................................................................................................any
Weight...................................................................................................................................................................... ≤55 g
6.2 Ordering information
Type Measuring
range Frequency range Art. No.
RCMA126P1-S 0…30 / 100 mA 0…500 Hz B 9404 2085