What are the components of an AC motor starter?

The components of an AC motor starter

The starter for AC motor is a device used to start an AC motor, and its main components include several key parts:

1. Electromagnetic Components

Electromagnetic components are one of the core parts of an AC motor starter. They use electromagnetic principles to connect and disconnect the starter and the motor. When the starter is connected to the power supply, current flows through the coil to generate a magnetic field. This magnetic field attracts the iron core in the starter, causing it to move. The movement of the iron core causes the mechanical switch in the starter to close, connecting the power supply to the coil of the motor and allowing the motor to start running.

2. Control Circuit

The control circuit is used to implement the start and stop control of the motor. When it is necessary to start the motor, the control circuit will send a start signal to the starter, which will connect the power supply and thus start the motor. When it is necessary to stop the motor, the control circuit will send a stop signal to the starter, which will disconnect the power supply and thus stop the operation of the motor.

3. Main Contactor

The main contactor is used to control the starting and stopping of the motor and is an important component of the starter. It can connect the power supply when the motor starts and disconnect the power supply when the motor stops.

4. Thermal relay

A thermal relay is used to protect electric motors from damage caused by overloads and short circuits. When a current of 1.2 times the rated current flows through it, the thermal relay can automatically trip and cut off the power within 20 minutes.

5. Button Switch

The button switch is used for manual control of the motor's start, stop, and direction change. By operating the button switch, remote control of the motor can be achieved.

6. Auxiliary Components

Assisting components include filters and contactors. Filters are used to eliminate electromagnetic interference generated during the operation of the motor, ensuring the normal functioning of the motor. Contactors, on the other hand, are employed to control the direction of the motor, enabling forward and reverse functions.

7. Autotransformer (Autotransformer Voltage Reduction Starter)

Autotransformers are used for reduced voltage starting, where the autotransformer is used to reduce the voltage for infrequent starting of electric motors. Autotransformer voltage reduction starters can be equipped with overload protection, which will automatically trip and cut off the power within 20 minutes when the current reaches 1.2 times the rated current.

8. Time Relay (Star-Delta Starter)

The time relay is used in the star-delta starter to achieve the purpose of reduced voltage starting by changing the connection mode of the stator winding. The star-delta starter is suitable for low-voltage cage-type motors with delta winding during normal operation and six output terminals.

The above are the main components of the AC motor starter, and these components work together to ensure that the motor can start and run safely and efficiently.