As the most widely used power equipment, electric motors are the main source of power for other electromechanical equipment. Therefore, the normal output of the motor is a prerequisite to ensure the normal operation of the electromechanical equipment. The function of the motor protector is to provide comprehensive protection and control to the motor. When the motor has over-current, under-current, phase loss, phase loss, over-voltage, under-voltage, three-phase unbalance and other faults, it will alarm or protect and control. So far, motor protectors have almost penetrated into most of the power consumption fields, and they play an irreplaceable role in the national economy.
When the motor fails, the three-phase current will change. Therefore, through the detection of the three-phase running current, different protection methods can be determined according to the different nature of the running current, so as to protect the motor from power failure. The operation protection principle of the motor protector uses this method.
At present, there are mainly several types of motor protectors commonly used in my country: thermal relays, temperature relays, electronic motor protectors and intelligent motor protectors. Different types have different functions, precision and quality. The purpose of daily selection of motor protection devices is to enable the motor to give full play to its overload capacity while avoiding damage. Best, it can also improve the reliability of the electric drive system and the continuity of production. Therefore, the ideal motor protector needs to meet the excellent performance of reliability, economy and convenience.