Measuring a transformer’s winding (DC) resistance from one external terminal to another can reveal a great deal of information about the transformer. In addition to the obvious faulted winding (i.e., an open winding), more subtle problems can be detected. The DC current, in addition to flowing through the winding, must also flow through the off-load ratio adjusting switch (De-Energized Tap Changer or DETC) and the on-load ratio adjusting switch (Load Tap Changer or LTC), as well as numerous welded and mechanical connections.
The Vanguard TRM-403 Transformer Resistance Meter is a three phase transformer winding resistance meter that allows the user to connect all test cables to the transformer bushings.
The Vanguard TRM-403 can automatically demagnetize the inductive device under test, eliminating the manual task of demagnetizing the transformer core after a resistance test.
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.
Vanguard TRM-403 features:
• Perform three phase test on transformers 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 20A (TRM-203) and 1A to 40A (TRM-403)
• Computer-control via RS-232C, USB, or bluetooth interface
• Built-in 2.5″ wide thermal printer