Circuit arrangement for testing insulation by partial discharge technique

Claim 1

Apparatus for testing the insulation of a commutator type armature winding and for also separately checking the resistance of the winding which comprises, for insulation testing, an inductor-stator provided with a multi-coil winding and within which the armature is mounted in a non-rotative manner, means producing from test voltage pulses a rotary magnetic field within said inductor-stator including means for sequentially energizing said coils with corresponding test voltage pulses each of which has the configuration of a damped sinusoidal oscillation and which serve to induce corresponding voltage pulses in different portions of the armature winding, contact means engaged with the commutator segments and which connect the different portions of the armature winding with an active filter unit which serves to separate the high-frequency partial discharge components from the fundamental of the damped sinusoidal oscillation, and a discriminator connected to the output of said filter unit for determining whether or not the insulation on the armature winding is satisfactory; and which comprises for resistance testing, a test voltage source connected to successive pairs of the commutator segments through said contact means for effecting corresponding flows of test current through the corresponding parts of the armature winding, means for measuring the magnitude of the test currents which are indicative of the resistance of the winding parts, and a second discriminator connected to the output of said measuring means for determining whether or not the armature winding parts have satisfactory resistance values.