Vanguard WRM-10 User Manual
TM
WRM-10
TRANSFORMER WINDING RESISTANCE METER
USER’S MANUAL
Vanguard Instruments Company, Inc.
1520 S. Hellman Ave.
Ontario, California 91761, USA
TEL: (909) 923-9390
FAX: (909) 923-9391
June 2009
Revision 2
WRM-10 USER’S MANUAL REV 2
SAFETY SUMMARY
FOLLOW EXACT OPERATING PROCEDURES
Any deviation from the procedures described in this User’s Manual may create one or more
safety hazards, may damage the WRM-10, damage the test transformer, or cause errors in the
test results. Vanguard Instruments Company, Inc. assumes no liability for unsafe or improper
use of the WRM-10.
All safety precautions provided in this manual must be observed during all phases of testing
including test preparation, test lead connection, actual testing, and test lead disconnection.
SAFETY WARNING AND CAUTIONS
The WRM-10 shall be used only by trained operators. All transformers under test shall be offline and fully isolated.
DO NOT MODIFY TEST EQUIPMENT
To avoid the risk of introducing additional or unknown hazards, do not install substitute parts or
perform any unauthorized modification to any WRM-10 test unit. To ensure that all designed
safety features are maintained, it is highly recommended that repairs be performed only by
Vanguard Instruments Company factory personnel or by an authorized repair service provider.
Unauthorized modifications can cause safety hazards and will void the manufacturer’s
warranty.
WARNING
Do not remove test leads during a test. Failure to heed this warning can result in lethal
electrical shock to personnel and damage to the equipment.
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REV 2 WRM-10 USER’S MANUAL
TABLE OF CONTENTS
CONVENTIONS USED IN THIS DOCUMENT ..................................................................................... 1
1.0 INTRODUCTION .................................................................................................................. .. 2
1.1 General Description and Features ................................................................................... 2
1.3 Technical Specifications ................................................................................................... 3
1.4 WRM-10 Controls and Indicators .................................................................................... 4
2.0 PRE-TEST SETUP ................................................................................................................... 6
2.1 Operating Voltages .......................................................................................................... 6
3.0 OPERATING PROCEDURES ................................................................................................... 9
3.1 WRM-10 Cable Connections ............................................................................................ 9
3.2 General Procedures ....................................................................................................... 11
3.3 Performing Transformer Tests ....................................................................................... 12
3.3.1. Performing a Single Resistance Test ...................................................................... 12
3.3.2. Performing a Voltage Regulator Test ..................................................................... 14
3.4 User Diagnostic Mode .................................................................................................... 16
LIST OF FIGURES
Figure 1. WRM-10 Controls and Indicators .................................................................................... 4
Figure 2. 100 – 120 Vac Jumper Settings ........................................................................................ 6
Figure 3. 200 – 240 Vac Jumper Settings ........................................................................................ 6
Figure 4. Relay Location .................................................................................................................. 7
Figure 5. Typical WRM-10 Connections Diagram #1 ...................................................................... 9
Figure 6. Typical WRM-10 Connections Diagram #2 .................................................................... 10
Figure 7. Typical Dual Winding Connections Diagram .................................................................. 10
LIST OF TABLES
Table 1. WRM-10 Technical Specifications ..................................................................................... 3
Table 2. Functional Descriptions of WRM-10 Controls and Indicators .......................................... 5
Table 3. Voltage Selection Jumper Settings .................................................................................... 6
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WRM-10 USER’S MANUAL REV 2
CONVENTIONS USED IN THIS DOCUMENT
This document uses the following conventions:
• The WRM-10’s control knob is referenced as [CONTROL KNOB]
Menu names are referenced as “MENU NAME”
•
• WRM-10 LCD screen output is shown as:
MAIN MENU
<RUN TEST>
• Warning messages are indicated as:
Warning message
WARNING
• Important notes are indicated as:
Note details
NOTE
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REV 2 WRM-10 USER’S MANUAL
1.0 INTRODUCTION
1.1 General Description and Features
The WRM-10 is designed to accurately measure the winding resistance of highly inductive
power transformers. The unit’s dual resistance-reading input channels can measure two
winding resistances simultaneously. Four-wire (Kelvin) connections provide high accuracy
voltage reading and require no lead compensation. The WRM-10 provides stable resistance
readings of very large transformers by utilizing a 36 Vdc power supply capable of outputting up
to 10 Amperes. The resistance reading of a 100MVA transformer can be achieved in 5 minutes
or less. The unit’s power supply is cooled by heavy-duty fans designed for continuous
operation.
Since the WRM-10 can accurately measure resistances ranging from 1 micro-ohm to 2,000
ohms, it can also be used to measure EHV circuit-breaker contact resistance, motor winding
resistance, or any low resistance. In addition to measuring the resistance value, the WRM-10
also checks the “make-before-break” tap-switching sequences of voltage regulators and load
tap changers.
The WRM-10 is furnished with three 50-foot test cables, a ground cable, a power cord, and a
cable carrying bag. Each test cable lead is terminated with a quick-disconnect test clip.
1.2 Functional Description
The WRM-10’s operation is based on the electrical relationship described by Ohm’s law: R=V/I,
where I is a known current and V is the DC voltage measured across the unknown resistance.
The value of the unknown resistance is calculated by dividing the measured voltage by the
current which is calculated by the microprocessor. Calculated resistance readings are then
displayed on the unit’s back-lit LCD screen.
A special current source allows the WRM-10 to output up to 10 Amperes of test current. The
test current is automatically adjusted depending on the load resistance. For added safety, the
current source circuit is thermally protected. Also, a built-in discharge circuit automatically
discharges the stored energy in the transformer at the end of each test.
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1.3 Technical Specifications
Table 1. WRM-10 Technical Specifications
TYPE Portable transformer winding resistance meter
PHYSICAL SPECIFICATIONS 16.8”W x 12.6”H x 10.6”D (42.6 cm x 32.0 cm x 27 cm); Weight: 27 lbs
(12.2 kg)
INPUT POWER 100 – 120 Vac or 200-240 Vac (factory pre-set), 50/60 Hz
RESISTANCE READING
RANGE
ACCURACY 1 – 19,999 micro-ohms: ±0.5% reading, ±1 count
TEST VOLTAGE 36 Vdc max
TEST CURRENT RANGE Auto range, 10 Amperes max
DISPLAY Back-lit LCD Screen (16 characters by 2 lines); viewable in bright sunlight
CONTROL Single “turn-and-push” knob
COMPUTER INTERFACE RS-232C port (19,200 baud) used for factory calibration and diagnostics
SAFETY Designed to meet IEC61010 (1995), UL61010A-1, CSA-C22.2 standards
ENVIRONMENT Operating: -10˚C to 50˚ C (15˚F to +122˚ F); Storage: -30˚ C to 70˚ C (-
CABLES Three 50-foot test cables, ground cable, power cord and cable bag
OPTIONS Transportation case
WARRANTY One year on parts and labor
1 micro-ohm – 2,000 ohms
20 – 999 milli-ohms: ±1% reading, ±1 count;
1 – 2,000 ohms: ±1.5% reading, ±1 count
and low-light levels
22˚F to +158˚ F)
WRM-10 USER’S MANUAL REV 2
NOTE
The above specifications are valid at nominal operating voltage and at a
temperature of 25°C (77°F). Specifications may change without prior notice.
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