Many different tests are performed on rotating machines to determine their state and discover possible future failures. One of the tests that are used to determine electrical problems is the DC winding resistance measurement. For the purpose of measuring low resistance accurately, winding ohmmeters such as RMO-M Series are used. Simple and quick reliable DC resistance measurement is a basic maintenance task performed on electrical motors and generators.
The resistance measurement can help maintenance personnel to detect different problems in the stator and rotor windings:
- such as turn-to-turn short circuit;
- phase-to-phase short circuit;
- short-to-ground short circuit;
- loosen or corroded connections;
- bad soldering contacts and etc.
To measure accurately, four-points Kelvin measurement method is used. This means applying high current using current leads and measuring the voltage drop with the other two leads. The procedure is then repeated for all other phases.
Using RMO-M instruments, it is possible to reduce the testing time by measuring the resistance of up to three windings simultaneously. The only requirement is to have accessible stator or rotor terminals.
Three channels, four-point Kelvin measurement of resistance, enable users of RMO-M devices to obtain a simultaneous measurement of up to three windings in rotating machinery. This cuts down testing time significantly.
After the measurement, the demagnetization process is performed automatically with RMO-M winding ohmmeters.