The surge comparison tester is used to simultaneously test turn-to-turn,
coil-to-coil, and coil-to-ground insulation. The surge tester is an electronic
device that applies surge voltage stress between turns of a coil, between
phases, from winding to ground, and it can detect short-circuited turns in
windings under test. The surge voltage is of very short duration and therefore
will not damage the windings. However, the surge voltage can be
increased high enough so that insulation breakdown and arcing can
be observed. The surge comparison test can be used as a go or no-go test.
This test is a very useful diagnostic test for quality-control shop testing when
reconditioning or rewinding wound components and in the fi eld to detect
early impending winding insulation failures. Rewound and reconditioned
motors and generators should be given a surge comparison test before varnishing
so that winding faults, such as shorted turns or coils, reversed coil
groups or phases, and incorrect number of turns in a coil, can be corrected
before the windings are treated with varnish