YZW15(DW15)series universal auto air circuit breakers(herein after referred to as the breakers)are suitably used in AC 50Hz,rated current up to 4000A and rated working voltage up to 1140V(using frame level rated current 630A and below)and 380V (using frame level rated current 1000A and over)power distributing systems for power distribution and protection fo power supply circuit and power apparatus from overload, under voltage and short circuit.