Overload protection switch is a circuit protection device designed according to the actual needs of the electrical control industry. It adopts single-chip technology, has complete functions, reliable action, strong anti-interference ability, and adapts to the harsh working environment. It can provide effective protection for the electrical system, squirrel-cage motor, winding motor over current, short circuit, phase loss, phase imbalance, phase mismatch and starting process (avoiding starting over current).