Wrong surge measurement, should we replace or rewind the motor?

IONIO, we have a wrong surge measurement, should we replace or rewind the motor? A common question from the market and this requires a bit of explanation.

An example of an “unreliable” equation during surge is when a rotor is present in a three-phase motor.

Due to the unequal number of slots in the rotor and stator, some phase windings will “see” another rotor.

Because of this difference, a surge (phase-phase) measurement of a fully assembled motor will be ambiguous in some cases.

To check if this rotor is indeed affecting the surge measurement, one can rotate the rotor (if possible) 360 degrees and see if the 3 surge graphs move with the rotation of the rotor.

If this is indeed the case, we will at least know whether the rotor affects the surge test and is not an immediate reject.

In some situations it is not possible to rotate the axis, in which case one still has the option of performing the “Peak to Peak” measurement on single stages, in practice this requires a certain know-how from the person performing the measurements.

Want to know more about off-line measurements of E-motors? And keep the knowledge within your organisation up to date? IONIO provides tailor-made training courses on the most common off-line measurements