Measuring the DC conductor resistance of a rotating machine stator can reveal a lot of information about the machine.
It is always desirable to find out the existence of any resistance that is higher than the nameplate value, which might be caused by poor joints, corrosion or mechanical deformation of the stator winding.
The excessive electromagnetic force caused by overcurrent and vibration can lead to failure or partial failure of conductors. The wear of winding insulation caused by vibration can also lead to a turn-to-turn short fault of the winding.
By measuring the resistance accurately, the subtle change of conductor condition can be detected and allow corrective actions to be taken to avoid unexpected failure.
It is important to note that a stator winding is a high inductance object. Abrupt interruption of test current may introduce a very high voltage that places the tester in danger. Therefore, ohmmeters that are designed for large inductive objects are recommended for stator winding conductor resistance measurements.