THREE-PHASE SHORT-CIRCUIT TESTING METHOD

PURPOSE:To apply no excessive stress to a breaker to be tested by turning on turning-on devices having either of two phases among three phases almost at the crest value of the line voltage between the two phases, turning on the remaining device of one phase several ms later, and suppressing the making current crest value. CONSTITUTION:When a short-circuit test is conducted, the turning-on devices 89 of the U and V phases are turned on at a U-phase and a V-phase turning-on point (where the U-V line voltage reaches the crest value). A two-phase circuit is formed by the turning on the U phase and V phase. Then when the W phase is 5ms delayed by a timer, etc., and turned on, so that the U-V line voltage falls to the zero point. Then the W-phase current reaches the crest value. Consequently, the crest value of the W-phase current is suppressed and currents E/Z flow to the respective phases. Consequently, no excessive stress if applied to the breaker.