JPS6119941B

PURPOSE:To make the injection of the electric current which exceeds a breaking current point by the resultant current of di/dt above the breaking capacity of a test breaker and of which the resultant current after exceeding the current zero point does not pass by the zero point again possible by providing a current source for vibrating current and a current source for non-vibrating current to an equivalent tester for breakers by a synthesis test method. CONSTITUTION:A current source by a capacitor C1-a reactor L1 for discharge-a line reactor L2 and a non-vitrating current source by the capacitor C1-a resistance R1-a line reactor L2 are provided to an impulse circuit IMP as an injecting current source for arc extension. The large vibrating current by the C1-L1-L2 circuit is supplied at a decreased loss to increase the resultant current just before zero of the current I1 of the current source A beforehand, and the non-vibrating current of high di/dt by the C1-R1-L2 circuit is superposed in a negative polarity direction at a resultant current zero timing, whereby the zero point is passed by at the increased di/dt near the zero point of the resultant current, and the voltage value applied between the terminals of the test breaker of the moment when the resultant current goes zero is increased.