DIFFERENTIAL PROTECTOR FOR LOW-VOLTAGE ELECTRIC MACHINE

The utility model relates to a differential protector for low-voltage electric machines, which makes no use of an independent power supply and adopts that one end of three equivalent resistors or electrical inductances or capacitors is connected in parallel to the three-phase power supply line of an electric machine, and the other end is provided with a miniature temperature relay WJ and a relay LH[2] driven by a secondary current mutual inductor, and then three end heads are connected together to form into a neutral point. When the line has phase failure, short circuit, over current or excess temperature, the neutral point generates offset, and generates a voltage signal. After the signal is taken out, is rectified via diodes D[1] and D[2], is filtered by the filtering capacitor C[2], and is stabilized by a voltage stabilizing tube, the signal directly drives a relay J[1] controlling the power supply of the electric machine to motion, cuts off the power supply and protects the electric machine. The protector is suitable for 0.5-300KW electric machines, and the asymmetrical voltage is >=30V.