Apparatus for high voltage testing of insulated conductors and oscillator circuit for use with same

An apparatus for high voltage testing of the insulation of electrical conductors, the apparatus comprising:

• an electrode for passing through an insulated electrical conductor;
• and
• an oscillator circuit including:
• a transformer including a primary winding and at least one secondary winding, the secondary winding to be coupled across the electrode;
• at least one bipolar junction transistor employed in an oscillator loop and coupled to the primary winding of the transformer for producing high frequency voltage;
• at least one field effect transistor coupled in parallel with the bipolar junction transistor;
• and
• means for actuating the field effect transistor to conduct with the bipolar junction transistor upon excitation of the transformer windings and upon an oscillator signal in the oscillator loop reaching a predetermined voltage, whereby the current conducting through the primary winding is substantially shunted from the bipolar junction transistor to the field effect transistor to significantly reduce power loss otherwise occurring if the current were conducting through the bipolar junction transistor alone.