APS 3C Series User manual

3C Series AC & DC Load Operation Manual
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3C SERIES AC & DC LOAD OPERATION MANUAL Page 1 of 149
Operation Manual
3C Series – Rev 2.0 P/N 160929-10
3CSeries
ProgrammableAC&DCload
ADAPTIVE Power Systems
Worldwide Supplier of Power Equipment
TM
Copyright 2018, Adaptive Power Systems, Inc. (APS) • All Rights Reserved • No reproduction without written authorization from APS.

3C Series AC & DC Load Operation Manual
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3C Series AC & DC Load Operation Manual
Contents
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3C SERIES AC & DC LOAD OPERATION MANUAL Page 3 of 149
Table of Contents
1Contact Information....................................................................................................................................................... 8
2Warranty, Service & Safety............................................................................................................................................ 9
3Product Overview ........................................................................................................................................................ 13
3.2.1 Constant Current Mode............................................................................................................................................................................... 13
3.2.2 Linear Constant Current Mode (LIN)........................................................................................................................................................... 14
3.2.3 Constant Resistance Mode (CR).................................................................................................................................................................. 14
3.2.4 Constant Voltage Mode............................................................................................................................................................................... 14
3.2.5 Constant Power Mode................................................................................................................................................................................. 15
3.3.1 CC Mode Applications.................................................................................................................................................................................. 16
3.3.2 CR Mode Applications.................................................................................................................................................................................. 17
3.3.3 CV Mode Applications.................................................................................................................................................................................. 17
3.3.4 Constant Power Mode Battery Evaluation ................................................................................................................................................. 19
3.3.5 Battery Test Functions ................................................................................................................................................................................. 20
3.3.6 Fuse Test Mode............................................................................................................................................................................................ 21
3.3.7 AC Rectifier Mode ........................................................................................................................................................................................ 23
3.3.8 Inrush Current Mode ................................................................................................................................................................................... 24
3.3.9 Power Supply OCP Mode Testing................................................................................................................................................................ 25
3.3.10 Power Supply OPP Mode Testing................................................................................................................................................................ 27
3.3.11 Short Circuit Testing ..................................................................................................................................................................................... 29
3.7.1 Terminal RVL1-4 Specs................................................................................................................................................................................. 31
3.7.2 Terminal RNYBS8-4 Specs............................................................................................................................................................................ 32
3.7.3 Terminal PTV1-12 Specs .............................................................................................................................................................................. 32
4Technical Specifications ............................................................................................................................................... 33
4.10.1 Model 3C018-18 V-I Curve .......................................................................................................................................................................... 41
4.10.2 Model 3C028-18-EV V-I Curve..................................................................................................................................................................... 42
4.10.3 Model 3C028-28 V-I Curve .......................................................................................................................................................................... 43
4.10.4 Model 3C038-28-EV V-I Curve..................................................................................................................................................................... 44
4.10.5 Model 3C038-38 V-I Curve .......................................................................................................................................................................... 45
4.10.6 Model 3C056-56 V-I Curve .......................................................................................................................................................................... 46
4.10.7 Model 3C075-75 V-I Curve .......................................................................................................................................................................... 47
4.10.8 Model 3C112-112 V-I Curve ........................................................................................................................................................................ 48
4.10.9 Model 3C150-112 V-I Curve ........................................................................................................................................................................ 49
4.10.10 Model 3C188-112 V-I Curve ........................................................................................................................................................................ 50
4.10.11 Model 3C225-112 V-I Curve ........................................................................................................................................................................ 51
5Unpacking and Installation .......................................................................................................................................... 52
5.4.1 Fuse Replacement Procedure ..................................................................................................................................................................... 53

3C Series AC & DC Load Operation Manual
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5.12.1 GPIB Interface............................................................................................................................................................................................... 57
5.12.2 USB, LAN or RS232 Interfaces...................................................................................................................................................................... 57
5.13.1 Analog Terminal Block ................................................................................................................................................................................. 58
5.13.2 Load Wire Inductance Considerations........................................................................................................................................................ 58
6Front Panel Operation ................................................................................................................................................. 61
6.4.1 Synchronization Source Setting................................................................................................................................................................... 71
6.8.1 Storing Settings ............................................................................................................................................................................................ 76
6.8.2 Recalling Settings ......................................................................................................................................................................................... 76
6.9.1 Sequence EDIT mode................................................................................................................................................................................... 77
6.9.2 Sequence EDIT Mode Flow Chart................................................................................................................................................................ 78
6.9.3 Sequence TEST Mode .................................................................................................................................................................................. 79
6.9.4 Sequence TEST Mode Flow Chart ............................................................................................................................................................... 80
6.10.1 Last Setting Recall......................................................................................................................................................................................... 81
6.10.2 Factory Default Initial Settings..................................................................................................................................................................... 81
6.11.1 Over Voltage Protection .............................................................................................................................................................................. 87
6.11.2 Over Current Protection .............................................................................................................................................................................. 88
6.11.3 Over Power Protection ................................................................................................................................................................................ 88
6.11.4 Over Temperature Protection..................................................................................................................................................................... 88
7Real Panel Connections ............................................................................................................................................... 89
7.6.1 Isolated Output ............................................................................................................................................................................................ 92
8Remote Control Programming .................................................................................................................................... 93
8.3.1 Parenthesis ................................................................................................................................................................................................... 95
8.3.2 Terminators .................................................................................................................................................................................................. 95
8.4.1 Setting Commands....................................................................................................................................................................................... 96
8.4.1 Query Commands........................................................................................................................................................................................ 97
8.4.2 Limit Command Syntax................................................................................................................................................................................ 98
8.4.3 Stage Commands ......................................................................................................................................................................................... 98
8.4.4 System Commands ...................................................................................................................................................................................... 99
8.4.5 Measure Commands ................................................................................................................................................................................... 99
8.4.6 Auto Sequence Commands....................................................................................................................................................................... 100

3C Series AC & DC Load Operation Manual
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8.5.1 Setting Commands..................................................................................................................................................................................... 101
8.5.2 Query Commands...................................................................................................................................................................................... 102
8.5.3 Limit Command Syntax.............................................................................................................................................................................. 103
8.5.4 State Commands........................................................................................................................................................................................ 103
8.5.5 System Commands .................................................................................................................................................................................... 104
8.5.6 Measure Commands ................................................................................................................................................................................. 104
8.6.1 Setting Command Descriptions................................................................................................................................................................. 106
8.6.2 Limit Command Descriptions .................................................................................................................................................................... 111
8.6.3 State Command Descriptions.................................................................................................................................................................... 112
8.6.4 System Command Descriptions ................................................................................................................................................................ 115
8.6.5 State Command Descriptions.................................................................................................................................................................... 116
8.7.1 OCP Test Mode Commands ...................................................................................................................................................................... 117
8.7.2 OPP Test Mode Commands ...................................................................................................................................................................... 117
8.7.3 Short Circuit Test Mode Commands......................................................................................................................................................... 118
8.8.1 *ESE ............................................................................................................................................................................................................ 118
8.8.2 *ESR? .......................................................................................................................................................................................................... 119
8.8.3 *IDN? .......................................................................................................................................................................................................... 119
8.8.4 *OPC ........................................................................................................................................................................................................... 119
8.8.5 *RST ............................................................................................................................................................................................................ 120
8.8.6 *SRE ............................................................................................................................................................................................................ 120
8.8.7 *STB? .......................................................................................................................................................................................................... 121
9Master / Slave Mode Configuration.......................................................................................................................... 122
9.3.1 Wiring diagrams for Three Phase AC Load Configurations...................................................................................................................... 123
9.3.2 Input Configuration Mode Switch Options............................................................................................................................................... 124
9.4.1 Connections................................................................................................................................................................................................ 126
9.4.2 Suggested system bus cables are:............................................................................................................................................................. 126
9.5.1 Parallel or Boost Mode .............................................................................................................................................................................. 126
9.5.2 Three-Phase Modes................................................................................................................................................................................... 127
10 USB Driver Installation............................................................................................................................................... 131
11 LAN Driver Installation............................................................................................................................................... 134
12 Calibration .................................................................................................................................................................. 144
13 CE MARK Declaration of Conformity......................................................................................................................... 145
14 RoHS Material Content Declaration .......................................................................................................................... 146
INDEX ................................................................................................................................................................ 147

3C Series AC & DC Load Operation Manual
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Table of Tables
Table 3-1: Included Accessories ...................................................................................................................................31
Table 5-1: 3C Series AC+DC Load Ship Kit Content.......................................................................................................52
Table 6-1: Description of Display Readouts .................................................................................................................66
Table 6-2: Function Keypad Description ......................................................................................................................68
Table 6-3: WAVE Keypad Description ..........................................................................................................................69
Table 6-4: Test Function Keypad Description...............................................................................................................70
Table 6-5: Internal or External Sync Circuits ................................................................................................................72
Table 6-6: Model 3C018-18 Factory Settings...............................................................................................................81
Table 6-7: Model 3C028-18-EV Factory Settings .........................................................................................................82
Table 6-8: Model 3C028-28 Factory Settings...............................................................................................................82
Table 6-9: Model 3C038-28-EV Factory Settings .........................................................................................................83
Table 6-10: Model 3C038-38 Factory Settings.............................................................................................................83
Table 6-11: Model 3C038-38 Factory Settings.............................................................................................................84
Table 6-12: Model 3C075-75 Factory Settings.............................................................................................................84
Table 6-13: Model 3C112-112 Factory Settings...........................................................................................................85
Table 6-14: Model 3C150-112 Factory Settings...........................................................................................................85
Table 6-15: Model 3C188-112 Factory Settings...........................................................................................................86
Table 6-16: Model 3C225-112 Factory Settings...........................................................................................................86
Table 8-1: RS232 DB9 Pin Assignments .......................................................................................................................94
Table 8-2: Supported Command Terminators..............................................................................................................95
Table 8-3: Remote Control Setting Command Syntax - Short Form.............................................................................96
Table 8-4: Remote Control Query Command Syntax - Short Form ..............................................................................97
Table 8-5: Remote Control Limit Command Syntax.....................................................................................................98
Table 8-6: Stage Command Syntax..............................................................................................................................98
Table 8-7: System Commands Syntax ..........................................................................................................................99
Table 8-8: Measure Command Syntax.........................................................................................................................99
Table 8-9: Auto Sequence Command Syntax .............................................................................................................100
Table 8-10: Remote Control Setting Command Syntax - Complex Form....................................................................101
Table 8-11: Remote Control Query Command Syntax - Complex Form .....................................................................102
Table 8-12: Remote Control Limit Command Syntax - Complex Form .......................................................................103
Table 8-13: Stage Command Syntax - Complex Form................................................................................................104
Table 8-14: System Commands Syntax - Complex Form............................................................................................104
Table 8-15: Measure Command Syntax - Complex Form...........................................................................................104
Table 8-16: Event Status Enable Register ..................................................................................................................118
Table 8-17: Status Byte Register................................................................................................................................121
Table of Figures
Figure 3-1: 3C Series Available Test Modes Diagram ..................................................................................................15
Figure 3-2: CC Mode Applications................................................................................................................................16
Figure 3-3: CC LIN Mode Applications..........................................................................................................................16
Figure 3-4: CR Mode Applications................................................................................................................................17
Figure 3-5: CV Mode Applications................................................................................................................................18
Figure 3-6: CP Mode Battery Evaluation Applications.................................................................................................19
Figure 3-7: Battery Test Modes 1 ~ 3...........................................................................................................................20
Figure 3-8: Current Protection Device Categories........................................................................................................21
Figure 3-9: : Fuse Test Trip Mode - Normal and Turbo Mode......................................................................................22
Figure 3-10: Fuse Test Non-trip Mode - Normal and Turbo Mode...............................................................................22
Figure 3-11: AC Rectifier Test Mode ............................................................................................................................23

3C Series AC & DC Load Operation Manual
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Figure 4-1: Model 3C018-18 V-I Curve.........................................................................................................................41
Figure 4-2: Model 3C028-18-EV V-I Curve ...................................................................................................................42
Figure 4-3: Model 3C028-28 V-I Curve.........................................................................................................................43
Figure 4-4: Model 3C038-28-EV V-I Curve ...................................................................................................................44
Figure 4-5: Model 3C038-38 V-I Curve.........................................................................................................................45
Figure 4-6: Model 3C056-56 V-I Curve.........................................................................................................................46
Figure 4-7: Model 3C075-75 V-I Curve.........................................................................................................................47
Figure 4-8: Model 3C112-112 V-I Curve.......................................................................................................................48
Figure 4-9: Model 3C150-112 V-I Curve.......................................................................................................................49
Figure 4-10: Model 3C188-112 V-I Curve.....................................................................................................................50
Figure 4-11: Model 3C225-112 V-I Curve.....................................................................................................................51
Figure 5-1: AC Input Voltage Label ..............................................................................................................................52
Figure 5-2: AC Line Fuse Holder Location.....................................................................................................................53
Figure 5-3: 3C Series Chassis Rear Panel – GPIB Option Location................................................................................57
Figure 5-4: Analog I/O Connector ................................................................................................................................58
Figure 5-5: Cable induced input voltage drop..............................................................................................................59
Figure 5-6: Unstable condition waveform capture example........................................................................................60
Figure 5-7: Load Cable Length and Twisted Pairs........................................................................................................60
Figure 6-1: 3C Series Load Front Panel ........................................................................................................................61
Figure 6-2: Front Panel Display and Controls Call-outs................................................................................................62
Figure 6-3: Diagram of available Operating Modes ....................................................................................................73
Figure 6-4: Diagram of available Test Modes..............................................................................................................74
Figure 6-5: Sequence EDIT Mode Operation Flow Chart..............................................................................................78
Figure 6-6: Sequence TEST Mode Operation Flow Chart .............................................................................................80
Figure 7-1: Rear Panel Connector Locations................................................................................................................89
Figure 7-2: Internal and External Voltage Sense Connections .....................................................................................91
Figure 8-1: RS232 Connection to PC and DB9 Pin out..................................................................................................94
Figure 9-1: Parallel Load Connection .........................................................................................................................122
Figure 9-2: Three Phase Wye Connection .................................................................................................................123
Figure 9-3: Three Phase Delta Connection.................................................................................................................123
Figure 9-4: Three Phase AC Load Cabinet with MODE4 Switch Option .....................................................................124
Figure 9-5: Three Phase AC Load Cabinet Rear View.................................................................................................125
Figure 9-6: Parallel / Boost CC Mode Setup...............................................................................................................128
Figure 9-7: Parallel / Boost LIN Mode Setup..............................................................................................................128
Figure 9-8: 3-PHS CC Settings ....................................................................................................................................129
Figure 9-9: 3-PHS LIN Settings ...................................................................................................................................129
Figure 9-10: 3-PHS CR Settings ..................................................................................................................................129
Figure 9-11: 3-PHS CP Settings ..................................................................................................................................130
Figure 9-12: 3-PHS CV Settings ..................................................................................................................................130
Figure 10-1: USB Device Driver Download .................................................................................................................131
Figure 11-1: LAN IP Scanner Utility Program Download............................................................................................135

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1Contact Information
AMERICA/CANADA
Adaptive Power Systems, Inc.
Irvine, USA
Phone: [phone]
Fax: [phone]
Email: [e-mail]
EUROPE
Caltest Instruments GmbH.
Kappelrodeck, Germany
Phone: [phone]
Fax: [phone]
Email: [e-mail]
CHINA
PPST Shanghai Co. Ltd.
Shanghai, China
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Web: http://www.adaptivepower.com

3C Series AC & DC Load Operation Manual
Warranty, Service & Safety
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2Warranty, Service & Safety
Limited Warranty
Adaptive Power Systems, Inc. (APS) warrants each unit to be free from defects in material and
workmanship. For the period of one (1) year from the date of shipment to the purchaser, APS
will either repair or replace, at its sole discretion, any unit returned to the APS factory in Irvine,
California or one of its designated service facilities. It does not cover damage arising from
misuse of the unit or attempted field modifications or repairs. This warranty specifically
excludes damage to other equipment connected to this unit.
Upon notice from the purchaser within (30) days of shipment of units found to be defective in
material or workmanship, APS will pay all shipping charges for the repair or replacement. If
notice is received more than thirty (30) days from shipment, all shipping charges shall be paid by
the purchaser. Units returned on debit memos will not be accepted and will be returned
without repair.
This warranty is exclusive of all other warranties, expressed or implied.
Service and Spare Parts Limited Warranty
APS warrants repair work to be free from defects in material and workmanship for the period of
ninety (90) days from the invoice date. This Service and Spare Parts Limited Warranty applies to
replacement parts or to subassemblies only. All shipping and packaging charges are the sole
responsibility of the buyer. APS will not accept debit memos for returned power sources or for
subassemblies. Debit memos will cause return of power sources or assemblies without repair.
This warranty is exclusive of all other warranties, expressed or implied.
Safety Information
This chapter contains important information you should read BEFORE attempting to install and
power-up APS Equipment. The information in this chapter is provided for use by experienced
operators. Experienced operators understand the necessity of becoming familiar with, and then
observing, life-critical safety and installation issues. Topics in this chapter include:
•Safety Notices
•Warnings
•Cautions
•Preparation for Installation
•Installation Instructions
Make sure to familiarize yourself with the SAFETY SYMBOLS
shown on the next page. These symbols are used throughout this manual and relate to
important safety information and issues affecting the end user or operator.

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Warranty, Service & Safety
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SAFETY SYMBOLS
Direct current (DC)
Alternating current (AC)
Both direct and alternating current
Three-phase alternating current
Off (Supply)
On (Supply)
Protective Earth (ground) terminal
Caution: Refer to this manual before this Product.
Caution, risk of electric shock
Fuse

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Warranty, Service & Safety
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Safety Notices
SAFETY SUMMARY
The following general safety precautions must be observed during all phases of operation,
service, and repair of this instrument. Failure to comply with these precautions or with specific
warnings elsewhere in this manual violates safety standards of design, manufacture, and
intended use of the instrument. Adaptive Power Systems assumes no liability for the customer's
failure to comply with these requirements.
GENERAL
This product is a Safety Class 1 instrument (provided with a protective earth terminal). The
protective features of this product may be impaired if it is used in a manner not specified in the
operation instructions.
ENVIRONMENTAL CONDITIONS
This instrument is intended for indoor use in an installation category I, pollution degree 2
environments. It is designed to operate at a maximum relative humidity of 80% and at altitudes
of up to 2000 meters. Refer to the specifications tables for the ac mains voltage requirements
and ambient operating temperature range.
BEFORE APPLYING POWER
Verify that the product is set to match the available line voltage and the correct fuse is installed.
GROUND THE INSTRUMENT
This product is a Safety Class 1 instrument (provided with a protective earth terminal). To
minimize shock hazard, the instrument chassis and cabinet must be connected to an electrical
ground. The instrument must be connected to the AC power supply mains through a properly
rated three-conductor power cable, with the third wire firmly connected to an electrical ground
(safety ground) at the power outlet. Any interruption of the protective (grounding) conductor or
disconnection of the protective earth terminal will cause a potential shock hazard that could
result in personal injury.
FUSES
Only fuses with the required rated current, voltage, and specified type (normal blow, time delay,
etc.) should be used. Do not use repaired Fuses or short circuit the fuse holder. To do so could
cause a shock or fire hazard.
DO NOT OPERATE IN AN EXPLOSIVE ATMOSPHERE.
Do not operate the instrument in the presence of flammable gases or fumes.
KEEP AWAY FROM LIVE CIRCUITS.
Operating personnel must not remove instrument covers. Component replacement and internal
adjustments must be made by qualified service personnel. Do not replace components with
power cable connected. Under certain conditions, dangerous voltages may exist even with the
power cable removed. To avoid injuries, always disconnect power, discharge circuits and
remove external voltage sources before touching components.

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Warranty, Service & Safety
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DO NOT SERVICE OR ADJUST ALONE.
Do not attempt internal service or adjustment unless another person, capable of rendering first
aid and resuscitation, is present.
DO NOT EXCEED INPUT RATINGS.
This instrument may be equipped with a line filter to reduce electromagnetic interference and
must be connected to a properly grounded receptacle to minimize electric shock hazard.
Operation at line voltages or frequencies in excess of those stated on the data plate may cause
leakage currents in excess of 5.0 mA peak.
DO NOT EXCEED LOAD INPUT VOLTAGE RATING.
WARNING
DO NOT EXCEED LOAD INPUT VOLTAGE RATING
This instrument does NOT have a means to disconnect its Load input from a
connected power supply. If the voltage applied to the Load input exceeds its
maximum rating – even if the load is turned completely off – damage to the load
WILL occur. Damage caused by exceeded maximum load input voltage under any
circumstance is NOT covered by the manufacturer’s product warranty. Remove any
load input connections when the load is not in use, even when it is turned off.
DO NOT SUBSTITUTE PARTS OR MODIFY INSTRUMENT.
Because of the danger of introducing additional hazards, do not install substitute parts or
perform any unauthorized modification to the instrument. Return the instrument to an Adaptive
Power Systems Sales and Service Office for service and repair to ensure that safety features are
maintained.
Instruments that appear damaged or defective should be made inoperative and secured against
unintended operation until they can be repaired by qualified service personnel.

3C Series AC & DC Load Operation Manual
Product Overview
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3Product Overview
This chapter provides an overview of the APS 3C Series programmable AC & DC loads. It
introduces the reader to general operating characteristics of these loads.
General Description
The APS 3C Series electronic load is designed to test, evaluation and burn-in of AC or DC power
supplies and batteries. The APS 3C Series electronic load can be operated from the front panel
(manual mode) or using remote control via one of its optional digital interfaces.
The VI curve constant power contours of the various 3C Series models are shown in the
Technical Specification Section. Maximum current and power capability depends on the specific
model.
Operating Modes
Available operating modes for all models are:
•Constant Current (CC) mode
•Linear Constant Current (LIN) mode
•Constant Resistance (CR) mode
•Constant Voltage mode
•Constant Power mode
•UPS Efficiency mode
•PV System Efficiency mode
•UPS Backup Test mode
•Fuse Test mode
A more detailed explanation of each mode and under what condition each mode is most
appropriate to use follows.
3.2.1 Constant Current Mode
This is the most commonly used mode of operating
when testing a voltage source such as an AC power
source, DC supply or battery. In this mode of
operation, the load will sink a constant level of
current as set by the user, regardless of any voltage
variations. A real time feedback loop ensures a
stable current under any voltage variation of the
AC source, DC supply or battery.
This mode is recommended for load regulation
testing, loop stability testing, battery discharge
testing and any other form of voltage regulation
loop testing.
VOLTAGE
CURRENT
V
I

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Product Overview
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3.2.2 Linear Constant Current Mode (LIN)
When operating in linear constant current mode,
the load current input into the 3C Series load
depends on the current setting regardless of the
input voltage, e.g., the current rms level remains
unchanged. The load current will follow the input
voltage waveform in real-time.
The LIN mode is implemented through a high-
bandwidth auto gain control circuit (ACG) and the
ACG output current control signal will track the
input voltage. The AGC circuit produces a constant
amplitude output signal so long as the amplitude of the input signal exceeds an adjustable
reference voltage applied to the peak detector. The reference voltage may be changed to
change the range of input voltage resulting in a constant-amplitude output.
The AGC circuit responds almost instantly to adjust for a sudden increase in input voltage. This
fast voltage transient response makes the LIN mode especially suitable for non-sinusoidal AC
voltage inputs such as step waveform, square waveform and any AC input voltage with a highly
distorted waveform.
3.2.3 Constant Resistance Mode (CR)
In Constant Resistance mode, the load will sink current directly proportional to the sensed input
voltage. The ratio between voltage and current is linear per ohms law and can be set by the user
within the operating range of the AC & DC load. The current is defined by the formula shown
here where R is the set value in CR mode and V is the AC or DC input voltage from the unit under
test.
=/
CR mode is useful for battery discharge testing of battery systems used to power constant
impedance loads as the voltage will decrease as the battery discharges over time resulting in
reduced current sinking.
3.2.4 Constant Voltage Mode
In Constant Voltage mode, the load will attempt to sink
as much current as needed to reach the programmed
voltage setting. This mode should only be used with
current controlled DC power sources.
Note: Most power supplies and sources are voltage
controlled, i.e. they regulate the output voltage to a
predefined voltage level. Such voltage supplies should
not be tested using CV mode as the supply voltage
regulation loop will conflict with the load control loop.
CURRENT I
VOLTAGE
V
VOLTAGE
CURRENT
V
I

3C Series AC & DC Load Operation Manual
Product Overview
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3C SERIES AC & DC LOAD OPERATION MANUAL Page 15 of 149
3.2.5 Constant Power Mode
In Constant Power mode, the load will attempt to
maintain the programmed Power dissipation by sinking
more or less current at the voltage sensed. The current is
defined by the formula shown below.
=/
Constant power mode is useful for battery discharge
testing as it simulates constant power drain on the
battery, regardless of battery charge state.
Load Applications & Test Modes
This section covers various load applications and special test modes that are available on the 3C
Series AC+DC Loads. The figure below shows the various test modes for either AC and/or DC
applications.
Figure 3-1: 3C Series Available Test Modes Diagram
VOLTAGE
CURRENT
V
I

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Product Overview
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3.3.1 CC Mode Applications
The Constant Current (CC) mode is ideal for testing the Load Regulation, Cross Regulation,
Output Voltage and Dynamic Regulation of a voltage power supply. The CC mode can also be
used to test the Discharge Characteristics and the Life Cycle of cells and battery packs. In CC
mode, the load can operate as a static load with switchable high and low current levels. It is also
possible to operate the load dynamically enabling the user to adjust sink current with time.
Figure 3-2: CC Mode Applications
Linear CC Mode (LIN)
During Linear C.C. mode, the load current input into the load depends on the current setting
regardless of the input voltage, e.g., the current setting remains unchanged. The load input
current waveform follows the input voltage waveform.
The LIN mode uses an Automatic Gain Control (AGC) circuit. The circuit will response to the
input voltage. The AGC circuit produces a constant amplitude output signal as long as the
amplitude of the input voltage exceeds an adjustable reference voltage applied to the peak
detector. The reference voltage may be changed to change the range of input voltage resulting
in a constant-amplitude output. The AGC circuit responds almost instantly to changes a sudden
increase in input voltage.
Figure 3-3: CC LIN Mode Applications
The AGC circuit is especially suitable for Step waveform, Square waveform and the AC input
voltage sinewaves with high levels of distortion. Examples are DC/AC inverters and UPS’s.

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3.3.2 CR Mode Applications
Operating in Constant Resistance mode is useful for testing both voltage and current sources.
The CR mode is particularly suited for evaluation the ‘soft start’ behavior of power supplies. This
is explained in more detail below.
Power Supply Start-up Sequence Tests
With the load set to constant current mode, the current demand at initial ‘Load ON’ of the
preset current value is almost instantaneous. This might cause problems for the Device under
Test (DUT) if it is unable to satisfy this relatively high current demand at initial switch-on.
For example, a 5V/50A output power
supply may not be able to deliver 50A
over its entire start-up range of 0-5
volts. In many cases the power supply’s
short circuit or over current protection
circuit will cause the power supply to
shut down under this scenario. This is
because the power supply is trying to
deliver the 50A at a voltage level that is
too low.
The answer to this problem is not to
use CC mode but to use CR mode
instead. This is because in CR mode the
current and voltage ramp up together
providing a ‘soft start’ when compared
to standard CC mode.
Note also that the load allows an
adjustable current ramp. This feature is
found under dynamic settings as RISE slew rate. Even in static mode the series load will regulate
its current demand at ‘Load ON’ in line with the adjusted RISE slew rate. The FALL slew rate also
in the dynamic settings allows the current ramp down to be controlled at ‘Load OFF’.
3.3.3 CV Mode Applications
In Constant Voltage (CV) operation, the load will attempt to sink as much current as required in
order to reach the set voltage value. CV operation is useful in checking the load regulation of dc
current sources. The CV mode is also ideal for characterizing the current limit of dc power
supplies.
Current source testing.
A common application for a dc current source is as a battery charger. Most battery chargers are
designed to automatically adjust their charging current according to the battery voltage. In CV
mode, the electronic load will sink the current that is needed to reach the desired voltage. The
CV mode is therefore ideal for checking the charge current at a particular voltage level.
Figure 3-4: CR Mode Applications

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If the battery charger is tested at a number of different voltage levels in CV mode, a current
curve can be recorded. Thus, the battery charger’s load regulation can be checked during
development and production testing.
Power supply current limit characterization
The current limit function is a necessary feature for all power supplies. A fold back current limit
curve is very common for fixed output switching power supplies. A constant current limit curve
is more popular for adjustable laboratory power supplies.
It is very difficult or near impossible to find the current limit curve by using CC or CR mode.
However, it becomes simple by using CV mode. The user sets the CV voltage and records the
output current. Plotting the current measurements against the voltage settings results in the
output current limit curve of a power supply.
Figure 3-5: CV Mode Applications

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3.3.4 Constant Power Mode Battery Evaluation
Primary or secondary batteries are the power source for a wide range of portable electronics
products, such as notebook computers, video cameras and mobile phones. To ensure long usage
times and customer satisfaction, the battery pack should be able to provide a constant power
for the longest time possible.
This can be measured, as the output voltage of a battery will drop over time. The rate of voltage
decay depends on a number of factors including duty cycle, chemistry type, battery age and
ambient temperature.
So to keep the device powered for the longest possible time the battery must be able to provide
a stable power output regardless of output voltage. In order to maintain a constant power the
output current will need to increase over time to compensate for the reducing voltage.
Operating the 3C Series electronic load in CP mode is ideal for testing the characteristics of a
battery. This is because as the battery voltage drops the load current will automatically increase
in order to keep the CP setting. By logging sink values against time the test engineer can also
measure the battery’s energy capacity at various discharge rates.
The 3C Series load also features an adjustable Load OFF setting. This allows a voltage level to be
set so that the electronic load automatically stops sinking power upon reaching this preset
voltage. This function can be used to ensure the battery is not subjected to a damaging deep
cycle discharge.
Along with static operation, the load can also be operated dynamically in CP mode. The dynamic
functions allow the ramp, fall and plateau times to be adjusted between two levels of power.
This capability means that ‘real world’ loads can be more accurately simulated. For example, the
dynamic mode could be used to test the performance of a battery that is required to provide
power pulses to transmit data from a radio frequency terminal.
Figure 3-6: CP Mode Battery Evaluation Applications

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3.3.5 Battery Test Functions
The 3C Series AC & DC electronic load has three dedicated battery test modes called TYPE1,
TYPE2 and TYPE3. All are different forms of discharge tests. The user can select the desired
battery test mode as needed. Test results are displayed on the LCD display and include battery
AH capacity, remaining battery voltage after discharge and the cumulative discharge time data.
Figure 3-7: Battery Test Modes 1 ~ 3