Abstract A surge tester simultaneously applies oppositely polarized surge pulses to a test winding and a standard winding. If there is an unbalance in the electrical characteristics of the two windings, a difference voltage representative of the difference in the voltages developed across the windings is applied to a fault detecting circuit. If the unbalance is sufficiently great, a fault indication is provided. A fault indicator circuit includes an electronic control device arranged so that it can be gated into a conductive condition in response to a fault condition only during half cycles of line voltage of one polarity and the surge pulses are applied to the windings only during half cycles of the opposite polarity. The magnitude of the difference voltage, representative of an unbalance condition, is compared against a reference voltage which varies in accordance with fluctuations in the line voltage. A ground fault condition is represented by an oscillatory voltage and this is detected by providing a fault indication only if the number of pulsations of the oscillatory voltage attains a given pulse count within a given period of time.
Apparatus for surge testing a winding to determine the presence of a ground fault by virtue of an electrical connection, at least when a surge voltage pulse is applied to said winding, between said winding and an associated electrically conductive core member comprising: capacitor means connected between said winding and said core member; means for applying a surge voltage pulse to said winding so that if a said ground fault exists, a damped oscillatory output voltage is provided across said capacitor means; and ground fault detector means for receiving a said oscillatory output voltage and providing an output indication representative of a said ground fault as a function of the number of pulsations of said oscillatory voltage during a given period of time.
Claim 2
Dependent Claim
123 words
Apparatus for surge testing a winding to determine the presence of a ground fault by virtue of an electrical connection, at least when a surge voltage pulse is applied to said winding, between said winding and an associated electrically conductive core member comprising: capacitor means connected between said winding and said core member; means for applying a surge voltage pulse to said winding so that if a said ground fault exists, a damped oscillatory output voltage is provided across said capacitor means; and ground fault detector means for receiving a said oscillatory output voltage and providing an output indication representative of a said ground fault as a function of the number of pulsations of said oscillatory voltage during a given period of time.
Claim 3
Dependent Claim
123 words
Apparatus for surge testing a winding to determine the presence of a ground fault by virtue of an electrical connection, at least when a surge voltage pulse is applied to said winding, between said winding and an associated electrically conductive core member comprising: capacitor means connected between said winding and said core member; means for applying a surge voltage pulse to said winding so that if a said ground fault exists, a damped oscillatory output voltage is provided across said capacitor means; and ground fault detector means for receiving a said oscillatory output voltage and providing an output indication representative of a said ground fault as a function of the number of pulsations of said oscillatory voltage during a given period of time.
Claim 4
Dependent Claim
123 words
Apparatus for surge testing a winding to determine the presence of a ground fault by virtue of an electrical connection, at least when a surge voltage pulse is applied to said winding, between said winding and an associated electrically conductive core member comprising: capacitor means connected between said winding and said core member; means for applying a surge voltage pulse to said winding so that if a said ground fault exists, a damped oscillatory output voltage is provided across said capacitor means; and ground fault detector means for receiving a said oscillatory output voltage and providing an output indication representative of a said ground fault as a function of the number of pulsations of said oscillatory voltage during a given period of time.
Claim 5
Dependent Claim
63 words
Apparatus as set forth in claim 1 including time delay means responsive to the first of said pulsations for timing a said given period of time and providing a trigger signal, resettable counting means for counting said pulsations and providing a fault signal only in the event that N pulsations have been counted before said counting means is reset by said trigger signal.