Study On Intelligent Integration Protector Of Motor

The production process are broken frequently due to the motor in operation are damaged, which is caused by abnormally running conditions. The intelligent motor protectors can be used, which will protect the abnormally running motors from damage, to minimize the malfunction time and reduce the economic losses.In this paper, a single-chip microcomputer, PIC16F877, based intelligent motor protector with functions of the overload protection, phase failure protection, ground protection, locked rotor protection and short-circuit protection is designed on the basis of analyzing the development and status quo of motor protectors in the world. The main work of the thesis is as follows. A method of using the Power System Blockset in Matlab to simulate the failures of motor is proposed. The analysis and calculation process are simplified because no differential equation need be solved. Taking 30kW asynchronous machine as a model, the current changes during the failures of motor are analyzed in detail. The relations between load torque and overload current, load torque and staring time, load torque and current of phase failure are given. On the basis of analyzing the running states of motor, the mathematic models for motor protection are built and several failure criterions are proposed. A single-chip microcomputer based intelligent motor protector is designed. The protection parameters can be set by user so that scope of application is stretched. A special artificial circuit is designed for short-circuit protecting together with digital protection so the reliability is ensured. The line current based power supply is designed for the protector to break the circuit when short circuit occurs.