Winding Resistance Ohmmeter WRM10

Quick and Accurate Measurements

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, and four-wire (Kelvin) connections provide high accuracy and require no lead compensation. The WRM-10 provides stable resistance readings of very large transformers by utilizing a 36Vdc 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" tapswitching sequences of voltage regulators and load tap changers. The WRM-10 is furnished with three 50-foot test cables. Each test cable lead is terminated with a quick-disconnect test clip.

Built-in Safety Features

At the end of each test, the WRM-10 automatically dissipates the stored energy in the transformer. This discharge circuit will continue to work even if the supply voltage is lost. For added safety, the unit's power supply is thermally protected from over-load damage.

User Interface

The WRM-10 features a back-lit LCD screen (16 characters by 2 lines) that is viewable in both bright sunlight and low-light levels. A "turn-and-push" knob is used to control the unit. A built-in RS-232C interface port is provided for diagnostic testing and firmware upgrades.