Abstract: In some factories, mining machinery and electrical equipment must be considered because of wrong phase sequence, causing the motor reversal will cause serious consequences, but the traditional phase protector for fault phase protection and phase state of a design problem incapable of action, protector, shaping the protector for three-phase incoming sampling, three respectively, to the logic of Fang Bo phase discrimination logic control unit, for the normal phase control unit generates a series of pulses LED light driven by a transistor, and LED encapsulated in the photosensitive resistance by light with the other switch tube bias and conduction, the contactor, electric motor starting operation; on the other hand, if the wrong sequence or lack of power phase indicator off, disconnect contactor, the motor stops rotating protection of personal property security. The protector can be made into a circuit module, at any time with any of a three-phase AC electromechanical equipment complete protection from work. Through the practical application of coal mine, the protector of flexible application, stable performance, high performance to price ratio.