• accurately measure resistance from 1 micro-ohm to 500 Ohms
• Perform three phase test on a transformer without the need to switch cables
• Can provide individual Delta winding resistance values
• Can provide individual Wye (with no neutral) winding resistance values
• Demagnetize transformer after test
• Selectable test current from 1A to 40A
• Computer control via RS-232C, USB, or Bluetooth interface
• Built-in 2.5" wide thermal printer

The TRM-403 is a  three phase transformer winding resistance meter that allow the user to connect all test cables to the transformer bushings. The unit will then measure the transformer resistance value for each of the phases without the need to disconnect and reconnect cables for each phase. The TRM-403 can provide a fast and stable reading of very large transformers by utilizing a 60Vdc power supply. It is capable of outputting a selectable test current from 1A to 40A. Since the TRM-403 can accurately measure resistance from 1 micro-ohm to 500 Ohms, it can be used as a micro-ohm meter to measure EHV circuit breaker contact resistance, or for any low resistance measuring application

For a Delta transformer, the TRM-203/403 can

measure the phase resistance readings and

provide the individual Delta winding resistance

values. The TRM-203/403 can also provide the

individual winding resistance values for a Wye

transformer without the neutral terminal.

If the transformer winding resistance temperature

is available at the time of testing, the TRM-

203/403 can calculate the equivalent resistance

value at any temperature value. This useful feature

can be used to compare the fi eld readings

against the factory test resistance values.

The TRM-203/403 can perform a special test to

collect data automatically for up to 90 minutes

(at 60-second sampling intervals) or 45 minutes

(at 30 second sampling intervals). The test data

is recorded with a time stamp.

All test results can be printed on the unit’s builtin

2.5” wide thermal printer. Test record header

information including the Company, substation

name, transformer information, and operator information

can also be entered using the rugged,

44–key “QWERTY”-style membrane keypad.

The TRM-203/403 can automatically demagnetize

the inductive device under test, eliminating

the manual task of demagnetizing the transformer

core after a resistance test.

The TRM-203/403 also has a “make-beforebreak”

test mode that can be used to test the

Load Tap Changer (LTC) or Voltage Regulator

contact test sequence. The TRM-203/403 produces

a “Dynamic-Resistance” graph of the LTC

or Voltage regulator contact under operation. An

opened contact can be detected visually from

this resistance chart.

The TRM’s built-in LTC/Voltage regulator can be

used to conveniently change the LTC/voltage

regulator tap position from the TRM-203/403

front panel.

ordering information

Part number TRM-203 TRM-203, cables, software

Part number TRM-403 TRM-403, cables, software

Part number TP3 2.5-inch wide thermal printer paper