What is a motor magnetic starter

A motor magnetic starter is an electromechanical device used to safely start and stop motors.

### Composition
– It consists of a steel – stamped housing, a steel base plate, an AC contactor, a thermal relay, and corresponding wiring. The AC contactor is the core component for controlling the on – off of the circuit. The thermal relay is used to provide overload protection for the controlled motor.

### Working Principle
– When the start button is pressed, the coil of the AC contactor inside the magnetic starter gets energized. The electromagnet attracts the armature, which drives the contact group to close, connecting the power supply of the electrical appliance (usually a motor). At the same time, it self – locks through the auxiliary contacts, so that the motor can keep running after the start button is released. When the stop button is pressed, the coil of the AC contactor loses power, the contacts open, cutting off the power supply of the electrical appliance and unlocking. According to different control requirements, the magnetic starter can be wired flexibly to achieve functions such as inching and phase – changing.

### Functions and Features
– **Overload Protection**: The thermal relay in the magnetic starter can monitor the current of the motor. When the motor is overloaded, the thermal relay will act according to the set current value, open the contact in series with the coil circuit of the AC contactor, cut off the power supply of the motor, and protect the motor from being damaged due to overload.
– **Under – Voltage Protection**: Due to the electromagnet in the contactor, if the power supply voltage is too low or the power fails, the contactor will automatically disengage, cutting off the power supply of the motor. When the power supply recovers, the motor will not start automatically until the start button is pressed again, which can prevent the motor from being damaged by low – voltage operation.
– **Easy to Operate and Control**: It can realize long – distance control of the motor’s start, stop, and reverse through the start – stop button switch, which is convenient for operation and management. And it has the advantages of simple maintenance and low cost.

### Application Scenarios
– Magnetic starters are widely used in industrial and commercial fields, covering almost all scenarios that require the use of motors or high – current load equipment. In industrial automation, they are usually used to control the start – stop processes of pumps, fans, crushers, air compressors, conveyor belts, and other equipment.