Wayne Kerr AP10030 Troubleshooting guide

Wayne Kerr
Wayne Kerr Wayne Kerr
Wayne Kerr
AP1kW Power Supplies
AP1kW Power SuppliesAP1kW Power Supplies
AP1kW Power Supplies
AP3080 AP6050 AP10030
AP3080 AP6050 AP10030AP3080 AP6050 AP10030
AP3080 AP6050 AP10030
User & Service Manual
User & Service ManualUser & Service Manual
User & Service Manual
Part Nº 9HAP1kW
Wayne Kerr Electronics Ltd
Durban Road, Bognor Regis, West Sussex, England PO22 9RL
Tel [phone] • Fax [phone]
Iss2 02/03/2009 12:08:00 PMA

2 Wayne Kerr AP 1kW Power Supplies • Issue 2


Wayne Kerr Electronics Ltd 1995
The copyright in this work is vested in Wayne Kerr Electronics Ltd and this document is issued for the purpose
only for which it is supplied. No licence is implied for the use of any patented feature. It must not be reproduced
in whole or in part, or used for tendering or manufacturing purposes except under an agreement or with the
consent in writing of and then only on the condition that this notice is included in any such reproduction.
Information furnished is believed to be accurate but no liability in respect of any use of it is accepted by Wayne
Kerr Electronics Ltd.

Wayne Kerr AP 1kW Power Supplies • Issue 2 3
CONTENTS
1. SAFETY ............................................................................................................................................................. 4
1.1 GENERAL............................................................................................................................................................ 4
1.2 A.C. POWER SUPPLY .......................................................................................................................................... 4
1.3 ADJUSTMENT,REPLACEMENT OF PARTS,MAINTENANCE AND REPAIR............................................................... 4
1.4 STATIC ELECTRICITY .......................................................................................................................................... 5
1.5 DISPOSAL HAZARDS ........................................................................................................................................... 5
1.6 LOAD INDUCTANCE ............................................................................................................................................ 5
2. SCHEDULE OF EQUIPMENT ....................................................................................................................... 6
3. INTRODUCTION ............................................................................................................................................. 7
4. SPECIFICATION ............................................................................................................................................. 8
5. INSTALLATION............................................................................................................................................. 12
5.1 SUPPLY VOLTAGE............................................................................................................................................. 12
5.2 MAINS CONNECTION ........................................................................................................................................ 13
5.3 LOCATION ........................................................................................................................................................ 13
5.4 RACK MOUNTING ............................................................................................................................................. 13
6. OPERATING INSTRUCTIONS.................................................................................................................... 15
6.1 FIRST TIME OPERATION.................................................................................................................................... 15
6.2 CONNECTING THE LOAD ................................................................................................................................... 16
6.3 PROTECTIVE CIRCUITS...................................................................................................................................... 17
6.4 OPERATING MODES .......................................................................................................................................... 20
6.5. LINE IMPEDANCE TEST.................................................................................................................................... 30
6.6. CURRENT MONITOR (IMON) ............................................................................................................................ 31
6.7. INHIBIT TERMINAL........................................................................................................................................... 31
7. CIRCUIT DESCRIPTION ............................................................................................................................. 32
8. RECALIBRATION ......................................................................................................................................... 36
8.1 EQUIPMENT NEEDED FOR RECALIBRATION ...................................................................................................... 36
8.2 RECALIBRATION PROCEDURE ........................................................................................................................... 37
8.3 OUTPUT NOISE AND RIPPLE MEASUREMENTS .................................................................................................. 40
9. MAINTENANCE ............................................................................................................................................ 42
9.1 CLEANING......................................................................................................................................................... 42
9.2 SAFETY CHECKS ............................................................................................................................................... 42
9.3 GUARANTEE ..................................................................................................................................................... 43
9.4 SERVICE ........................................................................................................................................................... 43
10. COMPONENT SCHEDULES...................................................................................................................... 44
11AP3080.............................................................................................................................................................. 45
11AP6050.............................................................................................................................................................. 50
11AP10030............................................................................................................................................................ 56
11. CIRCUIT DIAGRAMS ............................................................................................................................... 62

4 Wayne Kerr AP 1kW Power Supplies • Issue 2
1. SAFETY
1.1 General
This equipment has been designed to meet the requirements of EN61010 “Safety
requirements for electrical equipment for measurement, control & laboratory use”, and
has left the factory in a safe condition.
This product is not intended for use in atmospheres which are explosive, corrosive or
adversely polluted (e.g. containing conductive or excessive dust). It is not intended for
use in safety critical or medical applications.
The remainder of this section on safety provides information and warnings which must
be followed by the user to ensure safe operation and maintain the equipment in a safe
condition otherwise protection provided by the equipment may be impaired.
OPERATOR - Person who uses this equipment for its intended purpose. This person
should be suitably trained and aware of the hazards. Operators should be capable of fuse
replacement providing the normal precautions are taken.
1.2 A.C. Power Supply
1) It is necessary to fit a suitable a.c. power plug to the power cable, the user must
observe the following colour codes:
LIVE terminal to BROWN lead
NEUTRAL terminal to BLUE lead
EARTH terminal to GREEN/YELLOW lead.
The user must also ensure that the protective earth lead would be the last to break
should the cable be subject to excessive strain.
2) If the power cable electrical connection to the a.c. power plug is through screw
terminals then, to ensure reliable connections, any solder tinning of the cable wires
must be removed before fitting the plug.
3) WARNING! Any interruption of the protective earth conductor inside or outside the
equipment or disconnection of the protective earth terminal is likely to make the
equipment dangerous. Intentional interruption is prohibited.
4) Before switching on the equipment, ensure that it is set to the voltage of the local
a.c. power supply.
1.3 Adjustment, Replacement of Parts, Maintenance and Repair
1) When the equipment is connected to the local a.c. power supply internal terminals
may be live and the opening of the covers or removal of parts - including fuse
holders - (except those to which access can be gained by hand) is likely to expose
live parts. The equipment must be disconnected from all voltage sources before
it is opened for any adjustments, replacement (e.g. fuses), maintenance or
repair.
2) Capacitors inside the equipment may still be charged even if the equipment has been
disconnected from all voltage sources.

Wayne Kerr AP 1kW Power Supplies • Issue 2 5
3) Any adjustment, maintenance and repair of the opened equipment powered up must
be carried out by a skilled person who is aware of the hazards involved
4) Servicing personnel should be trained against unexpected hazards.
5) Ensure that only fuses with the required rated current and of the specified type are
used for replacement. The use of makeshift fuses and short circuiting of fuse holders
is prohibited.
1.4 Static Electricity
The unit supplied may use static sensitive devices and service personnel should be
alerted to components which require handling precautions to avoid damage by static
electrical discharge.
Before handling circuit board assemblies containing these components, personnel should
observe the following precautions:
1) The work surface should be a conductive grounded mat.
2) Soldering irons must be grounded and tools must be in contact with a conductive
surface to ground when not in use.
3) Any person handling static sensitive parts must wear a wrist strap which provides a
leaky path to ground, impedance not greater than 1 megaohm.
4) Components or circuit board assemblies must be stored in or on conductive foam or
mat while work is in progress.
5) New components should be kept in the supplier’s packaging until required for use.
1.5 Disposal Hazards
Service personnel should be aware that batteries should be disposed of intact and never
incinerated.
1.6 Load Inductance
Low voltage D.C. power supply products connected to large inductive loads can store
sufficient energy in the load to cause an electrical hazard. Extreme caution is
recommended when switching such circuits as back EMFs can reach dangerous levels.
WARNING
This equipment is intended for use by suitably trained and competent persons.
Under some conditions this product is capable of having hazardous voltages
(greater than 60V) on its terminals in normal use. Appropriate precautions should
be taken for safety.
This product can cause hazards if it is not used in accordance with these
instructions. Read them carefully and follow them in all respects. Double check
connections to the unit before use.
DO NOT USE THIS EQUIPMENT IF IT IS DAMAGED.

6 Wayne Kerr AP 1kW Power Supplies • Issue 2
2. SCHEDULE OF EQUIPMENT
The Power Supply has been carefully packed to prevent damage in transit.
The complete equipment comprises:-
Description Part Nº Qty
AP Power Supply 11AP3080 or
11AP6050 or
11AP10030
1
User & Service Manual 9HAP1kW 1
Spare Fuses 1A T Type FT1A00123 1
Rack Mounting Kit HB2529 1
Note: In the event of damage in transit or shortage in delivery, separate notices in writing
should be given to both the carriers and Wayne Kerr Electronics Limited, within three
days of receipt of the goods, followed by a complete claim within five days. All goods
which are subject of any claim for damage in transit or shortage in delivery should be
preserved intact as delivered for a period of seven days after making the claim, pending
inspection or instructions from Wayne Kerr Electronics Ltd., or an agent of this
company.

Wayne Kerr AP 1kW Power Supplies • Issue 2 7
3. INTRODUCTION
Autoranging - The AP series of autoranging bench\rack power supplies utilise
switching techniques to provide d.c. power up to 1kW over a wide range of voltage and
current combinations, thus obviating the need to select alternative output power supplies.
Precision - The units include full digital metering of both voltage and current. The
output of each power supply is adjustable from near zero to maximum volts and from
near zero to maximum amps by the 10 turn front panel controls. Alternatively, the
outputs can be controlled by the remote resistive or voltage programming facilities at the
rear of the unit, or, when fitted, by the IEEE488 interface.
Enable & Preview - The power supply output is enabled by the front panel ‘output
enable’ switch. When this switch is in the ‘button out’ position the front panel LED
meters and bargraphs display preview the output voltage and output current. This is done
without having to open circuit the load to set the voltage or short circuit the output to set
the current.
Displays - When in the ‘output enabled’ state, the meters and bargraphs display the
actual voltage and current being delivered to the load. The bargraph displays, in addition
to providing ‘trend’ indication, also allow the user to see at a glance, the current or
voltage availability.
Overvoltage Limit - To protect the load from the inadvertent application of an excessive
voltage, the power supply incorporates an ‘Overvoltage Limit’ (OVL). this causes the
supply to ‘down programme’ if the pre-set level has been exceeded. It can be adjusted by
rotating the ‘adjust OVL’ control through the front panel. In the local mode, this voltage
level can be monitored on the voltmeter by depressing the ‘Display OVL’ button.
Indicators - To enable the user to quickly assess the operating states, the power supply is
provided with LED indication of ‘output enabled’ and ‘CV’ or ‘CI’ operation. LED
indication is also provided of, an overtemperature condition (when any of the three heat-
sink assemblies have exceeded a safe operating temperature), an overvoltage condition
and of unregulated output (if the load demand exceeds 1kW d.c.).
Computer Control - An IEEE488 interface is available as a factory fitted option. When
fitted, this allows control of voltage and current and, in addition, provides ‘read back’ to
the controller of the actual voltage and current being delivered to the load. The IEEE488
option includes LEDs which indicate if the power supply is ‘talking’ or ‘listening’ or
whether a ‘service request’ signal has been sent.
System or Bench Use - The power supply can be used on the bench or rack mounted
using the brackets provided. All units are fan cooled.
Standards - The AP series is designed to meet generic emc standards. From 1st Jan 1997
this product will comply with Euro Norm safety standard EN61010-1.

8 Wayne Kerr AP 1kW Power Supplies • Issue 2
4. SPECIFICATION
All parameters measured with a resistive load.
Models Available Model Nº P max V range I range
AP30-80 1kW 0-30V 0-80A
AP60-50 1kW 0-60V 0-50A
AP100-30 1kW 0-100V 0-30A
A.C Input 230V±14% (198 to 263V) or 115V±14% (99 to132V) 48 to 63Hz
Internal link and selector switch to change for 115V operation.
Input Current 9A max. r.m.s. for 240V a.c. (20A peak), 20A max. r.m.s. for 115V a.c.
Inrush Current 31A max. for 240V a.c. 16A for 115V a.c.
Efficiency 80% typical at max. output power
D.C. Output See models available for voltage and current ranges.
10
20
30
20 40 60 80
34A
40A
50A
66.7A
80A
20
40
60
50
30
10
10 20 30 40 50
16.7A
20A
25A
33.5A40A 50A
100
80
60
40
20
10A
12.5A
16.7A
20A
25A
30A
10 20 30
34
Fig. 4a. AP3080 Fig. 4b AP 6050 Fig. 4c. AP10030
Output Control Three methods of control:
1. Front panel ten turn potentiometers.
2. Remote programming by resistance, voltage or current.
3. IEEE488 bus control
Resolution of Controls
0.07% typical of max. output voltage.
0.07% typical of max. output current.
Line Regulation
For a 10% change of a.c. input from
nominal
Less than 0.01% +3mV in constant voltage (CV) mode.
Less than 0.01% +5mA in constant current (CI) mode.
Load Regulation
For a zero to full load change
Less than ±0.01% ±5mV in CV mode.
Less than ±0.01% ±5mA in CI mode.

Wayne Kerr AP 1kW Power Supplies • Issue 2 9
Ripple and Noise
∆f = 20Hz to 20MHz
Typical 4mV r.m.s./40mV p-p
Max 7mV r.m.s./70mV p-p.(CV)
Typical 25mA r.m.s. Max 40mA r.m.s. (CI)
.
Temperature
Coefficient
Typical after 30 min. warm up
0.01% + 2mV per °C (CV)
0.01% + 4mA per °C (CI)
Stability Typical drift in output over an 8 hour interval (assuming constant line,
load and ambient temperature) after a 30 min. warm up
±0.03% of output ±5mV (CV)
±0.03% of output ±5mA (CI)
Output Impedance 0.2mΩat d.c., typical.
Load Inductance When using the power supply close to short circuit it is
recommended that all possible precautions are taken to maintain a low
load inductance. (Load leads should be short and where possible
twisted together.)
Response Time to
Transient Loads
Less than 2ms typical for output to recover within 100mV of nominal
(CV mode) following a change in output current of from 90-100% or
100-90% of maximum current.
Programming
Response Time
Maximum time for output voltage to change from 2 volts to maximum or
from maximum to 2V and settle within 200mV band:
UP Full load (3.4Ω) 120ms
No load 120ms
DOWN Full load (3.4Ω) 400ms
No load 1.2s
Overvoltage Limit
(OVL)
Front panel adjustable multiturn potentiometer. Trip level adjustable
from approx. 2V to a level above rated output voltage. Accuracy of trip
setting 1% approx. +1.5V.
Current Monitor 0-5V amplified current monitor output for zero to full output current.
accuracy 1% +10mV. Output impedance 5kΩnominal.
Remote Programming Resistance 0 to 4k7Ωprovides zero to full output voltage or current.
Common terminal connected to negative sense terminal.
Accuracy at 23°C 0.2% +60mV (CV) 1.1% +50mA (CI).
Voltage 0 to 5V provides zero to full output voltage or current.
Accuracy at 23°C 0.1% +60mV (CV) 1% +50mA (CI).
Remote Inhibit Input of a voltage between approx 2 and 60 volts to rear panel terminal
will shut down output.
Remote Sensing Maintains nominal voltage at load by correcting for up to 0.5V drop in
each output lead.

10 Wayne Kerr AP 1kW Power Supplies • Issue 2
E.M.C. Complies with EN50081-1 & EN50082-1 generic emissions and
immunity standards.
Note: This unit may exhibit deviance of up to 1% (CV mode) or 2% (CI
mode) in a 3V/m field.
Safety Standards Designed to comply with BS4743/IEC348.
After Jan 1st 1997 all units will be compliant with EN61010-1.
Metering And Status Twin 3 digit panel meters on front panel
Indication 12.5mm character height. High efficiency, red LED, digital display of
voltage and current output. Overvoltage limit (OVL trip point) can also
be displayed.
Twin bargraphs of 20 segments each give approximate indication of
voltage and current availability and will show trends.
Status flags give LED indication of CV and CI within panel meters.
Central status window indicates unregulated condition (UNREG),
overtemperature trip (OT), overvoltage limit (OVL). In addition, if the
IEEE488 bus option is fitted BUS indicates the unit is under bus control;
LSN indicates receiving data from the bus; TLK indicates transmitting
data on the bus; and SRQ indicates that a ‘service request’ has been
initiated
Meter Accuracy
Resolution & F.S.D
VOLTAGE
Accuracy at 23°C: ±0.2% rdg ±1 digit
Resolution: 100mV f.s.d 99.9V
CURRENT
Accuracy at 23°C: ±1% rdg ±1 digit
Resolution: 100mA f.s.d. 99.9A
IEEE (488) Interface
(When Fitted)
Refer to supplementary handbook (part no 9HAPHIBUS).
Float Voltage These units are designed for either terminal to be floated up to 120V
d.c. from earth, including the output voltage. The float sources must
be impulse free (see IEC 664) i.e. do not float the output on an
unisolated a.c. supply.
Environmental Operating temperature 0-40°C
Storage temperature -20 to +60°C
Cooling: Fan cooled. Air intake on front panel.
Overtemperature trip protection is featured.
RH <80% Non-condensing
Altitude <2000m
Pollution degree 2 - Normally non-conductive pollution.
Non-corrosive, non-explosive atmosphere.
Installation category 2 - Connected via a plug and socket to the supply.
For indoor use only.

Wayne Kerr AP 1kW Power Supplies • Issue 2 11
Mechanical Height 145mm )
Width 435mm ) approx overall dimensions
Depth 520mm )
Weight 16kg (20 kg shipping weight)
Rack Mounting Easily fitted into a standard 19” rack using mounting ears provided (see
Page 13 Section 5.4.). Support rear of unit in rack.
Panel Symbols Used
Refer to handbook.
Alternating current
Earth (ground) terminal
CAUTION - Risk of electric shock.
On
Off
ORDER CODES AP30-80 11AP3080
As above with IEEE488.2 interface
11AP3080/H =11AP3080+11APHIBUS1
AP60-50 11AP6050
As above with IEEE488.2 interface
11AP6050/H =AP6050+11APHIBUS2
AP10030 11AP10030
As above with IEEE488.2 interface
11AP10030/H =11AP10030+11APHIBUS3
We reserve the right to amend specifications without notification.

12 Wayne Kerr AP 1kW Power Supplies • Issue 2
5. INSTALLATION
5.1 Supply Voltage
Changing the supply voltage involves entering the unit and should be set by an agent or
by the factory when purchased. If the value specified on the rear panel is incorrect for
the installation then this task should be carried out by a qualified person. It is very
important that the unit is clearly marked subsequent to a change.
To change the input voltage setting proceed as follows:
1. Disconnect mains lead from supply and wait 15 minutes to allow capacitors to
discharge.
2. Remove the three fixing screws from each side trim.
3. Remove side trims.
4. Working from the front, and for each cover, slide backwards to clear recess in front
handles. Hinge cover away from the unit to just clear front handles and then pull
cover forwards.
Fig. 5.1 Unit Assembly
5. Having gained access to the interior and working from the top of the unit, locate the
voltage selector slide switch (accessible through the top plate) and adjust to the
appropriate setting.
6. For 115V operation, reconnect the orange link from the input reservoir capacitor to
the point marked 115V on the input filter board. Connect back to itself at the reservoir
capacitors for 230V operation.

Wayne Kerr AP 1kW Power Supplies • Issue 2 13
REAR
FRONT
Alternative connection
for 115V operation
115V Neutral O/P
Connection for 230V operation
Fig. 5.2 Changing Input Voltage
7. Amend the legend on the back panel to indicate the new voltage setting.
8. Finally, replace the covers and items previously removed.
5.2 Mains Connection
The unit is provided with a mains lead capable of handling the input current for both
115V and 230V operation. The free end of the lead should be connected via a suitable
plug (or, preferably, wired directly) to the local mains supply. The colour code employed
is as follows: Brown to Live, Blue to Neutral, Green/Yellow to Ground Safety Earth.
AP series power supplies are classified as Safety Class 1 equipment and it is imperative
that the mains earth lead (Green/Yellow) is connected to a known integrity earth
otherwise the chassis may float to a dangerous potential.
Due to the power supply incorporating an RFI filter, some earth leakage current (3 to
4mA) will flow. This may cause ‘nuisance’ tripping of the more sensitive type of earth
leakage circuit breakers.
The power supplies are intended for use with mains wiring capable of supplying the rated
input current without undue voltage drop. (See specification for maximum input
currents). The protective circuits (fuse or circuit breaker) must be capable of handling the
peak ‘in rush’ current without blowing or tripping. Unsatisfactory operation of the unit
may be due to low mains voltage caused by high a.c. line impedance. Check as stated in
Section 6.5.
5.3 Location
AP power supplies are intended for use either on the bench or in a rack. The units are fan
cooled and care must be taken not to restrict the air intake at the front or the exhausts at
the rear, top and bottom of the unit. If the power supply is rack mounted the exhaust must
not be subject to a static back pressure.
5.4 Rack Mounting
All models can be rack mounted in a standard 19” rack by using the two rack mounting
‘ears’ and the screws supplied. To fit these ‘ears’, carefully prise out the insert in the
outer face of both front handles (see diagrams) and store for future use. Fit each ear into
the recess formed by the removal of the insert and secure using the screws provided (M4
x 10 CSK). It is important that some provision be made to support the rear of the unit
when using the rack mounting ears.

14 Wayne Kerr AP 1kW Power Supplies • Issue 2
Procedure for attachment of rack mounting bracket
Insert small screwdriver into thin gap
between insert and handle body.
Prise away one end slightly and hold
in position with finger.
Note orientation of insert with styling
cut-out opposite cut out in handle
Insert screwdriver into other end and repeat
procedure. This will relieve the small tapered
pins of the insert from the threaded holes in the
handle. Remove insert in the direction of arrow.
Insert rack mounting bracket into
recess in handle in attitude shown
and secure firmly with 4 M4 x 10LG
C’SK HD screws supplied.
Fig 5.3 Rack Mounting Ears

Wayne Kerr AP 1kW Power Supplies • Issue 2 15
6. OPERATING INSTRUCTIONS
6.1 First Time Operation
General
Before turning ‘ON’, confirm that the unit is set to the correct mains input voltage and
that the mains earth lead is connected to ground. Remove the terminal cover and confirm
that links are in place on the barrier strip viz.:
+ linked to +sense (13 and 12)
- linked to -sense (11 and 10)
Vprog terminals 6, 7 and 8 connected together
Iprog terminals 3, 4 and 5 connected together
That + (13) and - (11) are wired to +ve and -ve busbar respectively.
Ensure that no load is connected
Replace the terminal cover. (The output of the power supply is inhibited with this cover
removed).
If the power supply is fitted with the IEEE488 option, ensure that the Bus connector is
disconnected and the Bus/Local switch is in the Local position. (Both items are located
on the back panel).
Fig 6.1 Front panel controls and indicators
Turn the voltage control 1and the current control 2, fully anticlockwise and the OVL
control 5 fully clockwise. Ensure that the output enable switch 3is in the button out
position.
Switch the power supply on by moving the circuit breaker 6upwards to the ‘ON’
position. The LED voltmeter and ammeter are now illuminated.
Rotate the voltage control fully clockwise, noting that the voltmeter and bargraph show
increased readings until at least the maximum output voltage of the unit is reached.
Repeat the above process using the current control and monitoring the ammeter and
associated bargraph. Ensure the readings reach at least the maximum output current of
the unit.

16 Wayne Kerr AP 1kW Power Supplies • Issue 2
Reset the voltage and current controls of the unit fully anticlockwise. Depress the “output
enable” switch 3. Note the adjacent green LED 7is illuminated and that either the CV
(Constant Voltage) or CI (Constant Current) legend is illuminated. Rotate the current
control one turn clockwise and note that only the CV legend is illuminated.
Note: under these conditions of demanding zero output, the ‘UNREG’ legend may also
be illuminated. This indicates that precisely zero output is not being achieved.
Whilst depressing the ‘display OVL’ button 4, rotate (with a suitable tool) the OVL
adjust control 5anticlockwise until a reading on the voltmeter of say 25V is reached.
Release the button and rotate the voltage control clockwise at the same time monitoring
the voltmeter. Confirm that when the voltage reaches the level of the pre-set OVL, the
voltmeter reading falls to approximately zero and the OVL legend is illuminated.
Reset the OVL circuit by rotating the voltage control fully anticlockwise, the OVL adjust
fully clockwise, releasing the ‘output enable’ switch and after 5 seconds, depress again to
‘enable’ the output.
Constant Current Check
Inhibit the output by releasing the ‘output enable’ switch, wait 30 seconds for the output
capacitors to discharge and then remove the protective terminal cover held by 2 M3
screws.
Short circuit the +ve and -ve bus bars (use wire capable of carrying the maximum current
that can flow i.e. for 50 amps use 10mm²) and then replace terminal cover.
Rotate the voltage control approximately one turn clockwise (from its fully anticlockwise
position) and rotate the current control fully anticlockwise.
Depress the ‘output enable’ switch and confirm that the CI legend is illuminated thus
indicating that the power supply is in constant current mode. Rotate the current control
clockwise. By reference to the front panel digital ammeter confirm that control of the
output current is available over the power supply’s output current range.
Release the ‘output enable’ switch and wait for 30 seconds. Remove the terminal cover
and the short circuit from the output. Replace the terminal cover. Read the remainder of
the operating instructions before connecting supply to actual load.
6.2 Connecting the Load
Load connections to the power supply are made to the busbars (marked +ve and -ve) at
the rear of the instrument. Access to these terminals is gained by removing the protective
cover. Load wires may be connected to any of the three pairs of connecting screws on the
busbars (6 x M5 bolts). Standard wires should have the appropriate size of termination
fitted. It is important that the wires to the load should be of sufficient gauge to avoid
overheating when carrying the current (set by the current limit point) that would flow if
the load were shorted. Generally, thicker wires than the minimum necessary to carry the
current are needed to obtain good regulation at the load. If the load regulation is critical,
then remote sensing should be used (see section 6.4.2.). To eliminate voltage spikes and
noise pick up, which could affect the power supply performance, these leads should be
twisted together, especially when operating with the load at a distance of greater than 1
metre. The leads should also be de-coupled by connecting a 1µF capacitor, adequately
voltage rated, across the load and as close as possible to it.

Wayne Kerr AP 1kW Power Supplies • Issue 2 17
Replace the protective terminal cover (it is held on by 2 x M3 screws) over the busbars
and the barrier strip before enabling the output. load leads may pass through the gap in
the bottom of the cover. N.B. The output is inhibited when this cover is removed.
Earthing the Load
Either the +ve or -ve busbar can be earthed to produce negative or positive voltages
relative to ground. A M5 threaded insert on the back panel (which is connected to ground
via the units mains lead) is provided to give a common earth point thus minimising earth
loop problems.
If neither terminal is connected to earth, the output can be floated up to a maximum of
120V d.c. (including output volts), away from earth potential. When a second earth is
added to the system a 200V float is permissable.
6.3 Protective Circuits
Circuits within the power supply will limit the output power or inhibit the system
operation (i.e. reduce output to zero) under certain conditions. LED enunciators on the
front panel indicate when one of the protection circuits is activated.
6.3.1 Overrange (UNREG)
An ‘over-range’ condition is indicated by the ‘UNREG’ (output unregulated) LED being
illuminated and no other LEDs in the status area being lit. The green output enable LED
will be illuminated.
The over-range condition occurs when the output power demanded from the supply
exceeds 1000W. The output does not shut down but will be limited with a constant
power output of just over 1000W. This condition will occur if the load connected is such
that neither the set voltage nor current limit setting can be reached without the load
taking more than 1000W.
Over-range may also occur if a current limit setting of greater than the maximum
specified output current is demanded.
6.3.2 Overvoltage Limit (OVL)
This circuit will operate whenever the output voltage exceeds that set by the overvoltage
adjust or when the output voltage exceeds a factory set overvoltage limit (approximately
10% greater than maximum output voltage).
The overvoltage trip is indicated by the ‘OVL’ LED being illuminated. The power supply
output will shut down, the meters will read approximately zero and no other indicators
(including the green output LED) will be illuminated.
Adjusting Overvoltage Trip
The trip point is adjustable by means of the multi-turn, screwdriver adjustable, ‘OVL
adjust’ on the front panel.
The trip setting can be seen by pressing the ‘display OVL’ button on the front panel. This
displays the overvoltage setting on the voltmeter. The setting can be viewed at any time
whether the power supply output is enabled or not. It is recommended that the trip point

18 Wayne Kerr AP 1kW Power Supplies • Issue 2
be set at least 2 volts above the output voltage normally required. This avoids the
possibility of false tripping.
Resetting Overvoltage Trip
To reset the overvoltage trip, release the ‘output enable’ push button, wait 5 seconds,
then depress the ‘output enable’ push button. If the power supply trips again, check the
OVL setting is in excess of the set output voltage. This may be done by comparing the
displayed OVL setting with the prospective output voltage (i.e. with output not
‘enabled’).
6.3.3 Overtemperature Protection
An overtemperature condition is indicated by ‘OT’ being illuminated in the status
section. The power supply output will shut down. The meters and bargraphs will read
approximately zero and no other LEDs will be lit.
This condition will occur if there has been overheating within the unit, e.g. due to fan
filter blockage, air intake/outlet restrictions or a too high ambient temperature. Refer to
instructions for filter cleaning (see section 9.1.).
Resetting Overtemperature Trip
When the unit has cooled sufficiently, the overtemperature trip can be reset in a similar
manner to the overvoltage trips i.e. releasing and then resetting the ‘output enable’
button. The trips should only be reset when the cause of the overheating has been
removed.
6.3.4 Low A.C. Mains Voltage Protection
If the a.c. mains input falls below approximately 70% of normal, the power supply will
shut down until the normal mains supply is restored (operation at low mains could cause
overheating and/or unreliable operation).
This condition is indicated by the ‘UNREG’ LED being illuminated. The green ‘enabled’
LED will remain lit, the output will be shut down and the meters will read approximately
zero.
N.B. - If the unit is operating with a mains input voltage near to the minimum specified it
is recommended that the mains impedance check be carried out (section 6.5.). If the
impedance is high the power supply may not be receiving adequate supply volts and this
may cause overheating.

Wayne Kerr AP 1kW Power Supplies • Issue 2 19
Front Panel Shows Condition
CV
LED
CI
LED
Enable
LED
UNREG
LED
OT
LED
OVL
LED
ENABLE
BUTTON
METER
     OUT Set volts &
Amps
Voltmeter & ammeter
reading preview volts &
amps set by the front
panel
      IN Output V & I Normal CV operation
meters read O/P volts and
current flowing.
      IN Output V & I Normal CI operation
meters read O/P volts and
current flowing.
      IN Output V & I Overrange condition.
      IN Zero Overtemperature trip
shutdown.
      IN Zero Overvoltage trip output
shutdown
   Lit for
short
periods
  IN Output V & I Occurs for short periods
when reducing O/P volts
with low load and indicates
dynamic bleed circuit is in
operation.
      IN Zero Low mains or mains
dropout.
      IN Zero Terminal cover removed
or “INHIB” in operation.
- Normal operation
Comment [PMA1]:

20 Wayne Kerr AP 1kW Power Supplies • Issue 2
6.4 Operating Modes
6.4.1 Normal Operating Mode
The unit is factory set for normal operation i.e. operation via front panel controls and
front panel sensing.
1 2 3
3
4
4
5
5
6
6
7
7
8
8
9 10 11 12 13
Inhib Imon
Iprog Vprog Common
-S -S -+S +
To -ve busbar
To +ve busbar
Fig. 6.2. Rear barrier strip linking for normal mode
Constant Voltage (CV)
Ensure that the ‘output enable’ switch is in the out position, wait 30 seconds and remove
the rear terminal cover. Connect the load leads to the output busbars. Refer to section
6.2. “Connecting the Load”. Connect the unit to a suitable supply and replace the rear
cover. Switch on by moving the circuit breaker to the ‘ON’ position.
The front panel voltmeter and ammeter will illuminate and display the values at which
the controls were set. Output voltage and current limit settings can now be set to the
required values. The overvoltage trip point can also be set. The ‘output enable’ switch
should now be depressed. Power will be applied to the load and the voltage and current
delivered to the load will be indicated on the AP units by the meters.
Provided that the current limit point has been set higher than the actual current flowing
into the load, then the ‘CV’ legend will be illuminated. Whenever the load current
reaches the previously set current limit figure, the power supply will automatically
change to constant current operation. This illuminates the CI legend and extinguishes the
CV legend. If the product of the current taken and the output voltage exceed 1kW (before
reaching the current limit setting) the output current will be limited by the internal power
limit circuit.
To avoid unwanted CV/CI crossover, an allowance should be made6.44 for the peak
currents taken by the load when setting the current limit level.
Constant Current (CI)
With the power supply switched on and the ‘output enable’ switch out, the ammeter will
display the prospective current limit setting. This setting may be adjusted by the front
panel control.
The output voltage should be set to a higher value than that which would be developed
across the load with the required constant current flowing.
When the ‘output enable’ switch is pressed in, power is applied to the load and the
meters indicate the voltage and current delivered to the load. If the voltage at the output
busbars is less than the voltage setting, the ‘CI’ legend will be illuminated. If the load
changes such that the voltage developed across it reaches the pre-set voltage level then