Surge Testing is an important and effective test. It not only tests ground insulation but more importantly, it tests turn-to-turn coil-to-coil and phase-to-phase insulation. If as few as one turn is shorted the surge test till detect this fault. Most winding failures start with a turn–to–turn short. Circulating currents in that shorted loop generate excess heat that eventually deteriorates the ground insulation. High voltage Surge Comparison Testing can detect faults before they shut down the motor. A majority of insulation faults start as weakness in the turn insulation. Holes in the wire insulation and damage during the winding process lead to shorts and quality problems. Aging during operation reduces the dielectric strength of the turn insulation.

With a Baker Surge Comparison Tester, these incipient faults can be detected before it shuts down the motor. The quality of the winding insulation is tested and assured. In repair and service, the condition of the winding insulation can be determined. When using this technique as a preventative maintenance tool, production shutdowns in industrial plants will be avoided.


Baker Surge Comparison Testers use extremely short high voltage pulses to test electric windings and their insulation. This surge creates a voltage difference between turns. The turn-to-turn insulation is tested for its quality. Turn-to-turn insulation weakness, incipient faults and all winding problems and faults are immediately visible on the oscilloscope screen of the Baker Tester.

The Baker Surge Comparison Tester applies two identical pulses to two windings or phases under test. This produces two wave patterns on the display of the instrument. If the windings match, their patterns will superimpose. A fault produces two separate patterns.

Additional to Surge Testing

A DC high-potential test is incorporated in a Baker Tester. The combination of both High Voltage Surge Comparison Testing and DC High Potential Testing in one instrument provides the most effective tool for assuring the quality of electric windings.