The air circuit breaker is an important protection device that has the responsibility to quickly automatically shut off the power system in the event of a failure in the low-voltage system, as well as to plan for transmission, power, and shutdown using air as a medium.

It is a core wound in a toroidal shape by stripping a material with high investment rate (Ni80%, thickness 0.07~0.1mm) and is mainly used as a CT core of a large-capacity ZCT core and an electronic wattmeter as the non-error rate and phase angle are close to zero even in a low current region (100mA).

It is used as a transformer core, an electronic motor protection relay (EMPR, EOCR), and a core for current sensors, using excellent straightness characteristics and high saturation points.