Osborne’s #13937T324 high impedance transformer has a 480 Volt, 60 Hertz input and a no-load output voltage of 600 Volts. Should the insulation of the motorette under test fail in a shorted condition, the impedance of this transformer has been calibrated to limit the short circuit current to the motorette to 11 Amps RMS. The 600 Volt output is used to test the dielectric strength between each winding and ground and from each winding to all other windings. In addition to the impedance of this transformer, the circuit incorporates a circuit breaker in series with the output to trip and open the output circuit in a time no greater than three (3) seconds.