Motor protector is a necessary protective component in the motor, which will provide timely protection when the motor encounters problems such as overheating, overload, undervoltage, and missing items. So what are the common types of motor protection? Let's take a look.

The most commonly used are bimetallic motor protectors, composite motor protectors, and intelligent motor protectors.

(1) Bimetal type motor protectors - Bimetal type protectors are divided into thermal protectors and overload protectors. The design principle is to use bimetallic sheets to make switches or relays, and use two layers of metal materials with different thermal expansion coefficients to form bimetallic sheets. The active layer has a high expansion coefficient, while the passive layer has a low expansion coefficient. When the temperature rises, the bimetallic sheet undergoes bending deformation due to different expansion coefficients. After the temperature recovers, the shape of the bimetallic sheet also recovers, forming a switch that closes and opens according to temperature changes.

A thermal protector is a type of protector that causes deformation of bimetallic sheets by heating the protected area. It is usually installed in a position with high winding temperature, and when the motor is detected to have ultra-high temperature, the circuit is instantly disconnected and protection is activated.

The design principle of overload protector and thermal protector is similar, except that it generates its own heat through its internal electric heating. When the current is too high, the temperature of the electric heater will be too high, causing deformation of the bimetallic sheet. Due to its large volume and slow response to temperature, it is different from the installation method of the thermal protector, and cannot be used as an external thermal protector.

(2) Composite Motor Protector - A composite motor protector is a type of motor protector that uses a thermistor+electronic module for protection. This protection needs to be achieved by changing the temperature of the thermistor, causing its resistance value to change, causing the control circuit inside the electronic module to close or open, thus forming a compressor switch. When the temperature of the thermistor is too high, its resistance value will sharply increase, causing the control circuit to open, thus stopping the compressor from working.

(3) Intelligent protector - This type of protector is usually used in industrial and mining enterprises, playing a comprehensive function of real-time measurement, protection, monitoring, display, communication, etc. It is often used for the protection and evaluation of low-voltage distribution network motors.