Apparatus for measuring insulation qualities of a material including plural shielding means surrounding the excitation voltage source

Claim 1

AN APPARATUS FOR THE MEASURMENT OF ELECTRICAL QUALITIES OF INSULATION BETWEEN TWO CONDUCTIVE POINTS OF CONNECTION, COMPRISING IN COMBINATION; A SOURCE OF ALTERNATING CURRENT HIGH VOLTAGE HAVING EXCITATION MEANS AND AT LEAST FIRST AND SECOND OUTPUT TERMINALS; A CONDUCTOR LEADING FROM THE FIRST OUTPUT TERMINALS TO ONE OF THE SAID POINTS OF CONNECTION; AN INNER SHIELDING MEANS ENVELOPING THE SAID SOURCE OF HIGH VOLTAGE AND THE SAID CONDUCTOR AND ELECTRICALLY CONNECTED TO THE SECOND OF SAID TERMINALS; AN OUTER SYSTEM OF SHIELDS SURROUNDING THE HIGH VOLTAGE SOURCE AN THE SAID CONDUCTOR AND ELECTRICALLY CONNECTED TO A POINT OF GROUND POTENTIAL; A CONTINUOUS ELECTRICAL PATH INTERCONNECTING THE OTHER OF SAID POINTS OF CONNECTIONS AND THE INNER SYSTEM OF SHIELDS, SAID PATH COMPRISING, CURRENT MEASURING MEANS; A SECOND SOURCE OF ALTERNATING CURRENT VOLTAGE HAVING FIRST AND SECOND OUTPUT TERMINALS, SAID FIRST TERMINAL ELECTRICALLY COMMON WITH THE SECOND TERMINAL OF THE HIGH VOLTAGE SOURCE, AND SAID SECOND SOURCE OF VOLTAGE ADAPTED TO PRODUCE A VOLTAGE AT ITS SAID SECOND TERMINAL WHICH IS OPPOSITE IN PHASE TO THE OUTPUT OF THE FIRST TERMINAL OF THE HIGH VOLTAGE SOURCE; AND CAPACITIVE MEANS CONNECTED BETWEEN A POINT OF GROUND PONTENTIAL AND THE SECOND TERMINAL OF THE SAID SECOND SOURCE OF ALTERNATING CURRENT VOLTAGE.