Our Samatic R15000 Series machine (USA Make) analyse the surge test generates a surge pulse in a motor’s windings, which results in a decaying oscillating waveform. The test instrument calculates the difference in waveforms either phase-to-phase or pulse-to-pulse. If the difference is above the operator’s pass/fail threshold, the motor has weak winding insulation . Surge tests are critical because they are the only test that finds turn-to-turn insulation weaknesses. These weaknesses start at voltages above the operating voltage of the motor and are precursors to serious failures and shutdown of a motor.