testing

Any motor that we receive for repair is given a “megger” test as the first line of diagnostics. This test checks the windings to “ground” (the frame of the motor).

A second test for the stator, if it passes the “megger” test, meaning we didn’t find a “grounded” winding, is a “hi-pot” test. Hi-pot stands for “high potential” test. The “hi-pot” test is to really see how good the insulation is. This test will also give us a “leakage” value of the current that “leaks” through the insulation to ground, and that value is rated in “milliamps” of DC current.

Assuming the winding passes the megger and hi-pot tests, the final test is a “surge test”. This test subjects the winding to pulses of electrical voltage and the data is displayed on a screen and looks like an electronic oscilloscope. The pulses are fed to EACH of the phases of a three-phase motor and the resultant display shows those “traces” on the screen. If the winding is GOOD, the 3 traces can be superimposed on each other and you will see what appears as a single trace. If there are 2 or more wires shorted together in the coils, the traces will NOT superimpose and you will see the multiple traces. The motor then needs to be rewound.