1 Due to full compensation of resonant reactive power the power of power supply and equipment is less than 1/10 of the required capacity of the subject (1/q10); Small size and light weight with the same capacity large output capacity of the device and small power capacity required for configuration cheap convenient and safe operation. 2 Series resonance is actually a current filtering circuit so that the current passing through the subject is basically the fundamental current and the waveform distortion rate (THD) of the output voltage is very small which is superior to all existing ac voltage withstand equipment. 3 The short circuit current of the sample after flashover or breakdown is only less than 1/10 (1/Q) of the test current before short circuit which can effectively prevent the expansion of damage to the fault point after breakdown. 4ã??After flashover the arc will be automatically extinguished immediately. The long (number of seconds) process of restoring resonant state voltage after arc quenching is a steady-state establishment process and there is no danger of voltage overshoot and no danger of restoring overvoltage in microsecond millisecond transient process.