I'd like to gather opinion on how widespread the use of surge testing on low voltage motors is and any areas of concern. I have a vendor who wants to either sell his testing service or the test equipment to me. He insists it is OK to do the surge test, however other people( motor rewinders) tell me not to use the test as it may in fact cause insulation stress and premature failure. They recommend this test only be carried out on new or rewound/reinsulated motors and should not be used on in-service machines. The motors generally are 415v 4 pole.

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It depends on the type of surge test being applied. The SKF Baker AWA, for instance, is a variation of the surge comparison test specifically designed for field service testing. It includes the ability to stop testing should certain thresholds be crossed. The type of testing is referred to as PD Surge in IEEE Std 1415-2006.

In the case of a standard surge test, it is normally not recommended for field testing due to the potential of contamination causing a path (Ref. ANSI/EASA AR100-2006). Normally, new windings, rewound motors, and windings that have been cleaned and dried first.

One of the issues that has been brought up frequently is more of an 'old wives tale.' That is that repeated stress testing of a winding will somehow degrade the winding. According to research performed and published by Sedding, Stone, et.al., using repeated high potential testing, this was found to be incorrect, as long as no damage exists (ie: a fault reading).

The minimum turn to turn voltage required is 350 V. (peak). Specific values for form-wound machines, both new and used insulation systems, can be found in IEEE Std 522-2004, "IEEE Guide for Testing Turn Insulation of Form-Wound STator Coils for Alternating-Current Electric Machines."

A standard currently in development is IEEE P1068 "Draft Standard for the Repair and Rewinding of AC Electric Motors in the Petroleum, Chemical and Process Industries." Per this draft standard, after the winding has been cleaned, "the required test levels are 1.21 times motor phase to phase rated voltage for a rise time of 0.1 microsecond, 1.4 times for 0.5 microseconds and 1.72 times for 1.2 microseconds."

While there is some risk as performing surge testing, of any type, on a winding can potentially cause damage, it can be used as a method of detecting potential winding and insulation to ground faults. It is recommended that you have a reasonable level of experience and knowledge about any high voltage test before you perform it.