What are the methods of braking three-phase asynchronous motors?

Braking of three-phase asynchronous motors is an important topic in the field of motor control. In practical applications, motors need to start, run, stop and other operations under different working conditions, and braking is one of the important means to achieve these operations. This article will introduce the braking methods of three-phase asynchronous motors in detail, including energy consumption braking, reverse braking, feedback braking, electromagnetic braking, etc., and conduct an in-depth analysis of the principles, characteristics, application scenarios, etc. of various braking methods.

1. Dynamic braking

Energy-consuming braking is a common braking method for three-phase asynchronous motors. The principle is to short-circuit the rotor winding of the motor so that the motor can continue to run after power failure. However, at this time, the rotor winding of the motor will generate a large current, thereby consuming the kinetic energy of the motor and achieving the purpose of braking.

The advantages of dynamic braking are simple structure, low cost, and applicable to various types of three-phase asynchronous motors. However, the disadvantage of dynamic braking is that a lot of heat will be generated during the braking process, and corresponding heat dissipation measures need to be taken, otherwise it may cause damage to the motor.

1.1 Working principle of dynamic braking

When the three-phase asynchronous motor is powered off, the current in the rotor winding still exists, but the motor speed will gradually decrease due to the lack of power drive. At this time, the current in the rotor winding will generate a large electromagnetic force, so that the motor continues to run. Since the rotor winding is short-circuited, the current is large, which will generate a large amount of heat, consume the kinetic energy of the motor, and achieve the purpose of braking.

1.2 Application scenarios of dynamic braking

Energy consumption braking is suitable for occasions that require rapid stopping, such as elevators, cranes, etc. In these occasions, the motor needs to stop running in a short time, and energy consumption braking can quickly consume the kinetic energy of the motor and achieve rapid braking.

1. Reverse braking

Reverse braking is a method of braking using the reverse electromotive force of the motor. The principle is to reverse the three-phase power supply of the motor after the motor is powered off, so that the rotor winding of the motor generates reverse current, thereby achieving braking.

The advantages of reverse braking are fast braking speed and good braking effect, which is suitable for occasions that require rapid braking. However, the disadvantage of reverse braking is that a large current shock will be generated during the braking process, which may cause damage to the motor and power supply system.

2.1 Working principle of reverse braking

When the three-phase asynchronous motor is powered off, the three-phase power supply of the motor is reversed, and the rotor winding of the motor will generate a reverse current. Due to the existence of the reverse current, the rotor winding of the motor will generate a large electromagnetic force, which will rapidly reduce the speed of the motor and achieve the purpose of braking.

2.2 Application scenarios of reverse braking

Reverse braking is suitable for occasions that require rapid braking and high braking effect, such as conveyor belts, cranes, etc. In these occasions, the motor needs to stop running in a short time and the braking effect is required to be stable and reliable.

1. Regenerative braking

Regenerative braking is a method of using the regenerative energy of the motor to achieve braking. Its principle is to short-circuit the motor's rotor winding during the motor's operation, so that the motor's rotor winding generates a large current, thereby consuming the motor's kinetic energy and achieving the purpose of braking.

The advantage of regenerative braking is that no heat is generated during braking, and the impact on the motor and power system is small. However, the disadvantage of regenerative braking is that the braking speed is slow, and it is suitable for occasions that require slow braking.

3.1 Working principle of regenerative braking

When the three-phase asynchronous motor is running, the motor's rotor winding is short-circuited, and a large current will be generated in the motor's rotor winding. Due to the existence of the current, the motor's rotor winding will generate a large electromagnetic force, which will gradually reduce the motor's speed and achieve the purpose of braking.

3.2 Application scenarios of regenerative braking

Regenerative braking is suitable for occasions where slow braking is required and the braking effect is not high, such as elevators, cranes, etc. In these occasions, the motor needs to stop running for a long time and the braking process is required to be smooth and reliable.

1. Electromagnetic brake

Electromagnetic braking is a method of braking using electromagnetic force. The principle is to install an electromagnet on the rotor of the motor and brake the motor by controlling the current of the electromagnet.

The advantages of electromagnetic braking are fast braking speed and good braking effect, which is suitable for occasions that require rapid braking. However, the disadvantages of electromagnetic braking are complex structure and high cost, which is suitable for occasions that require high braking effect.

4.1 Working principle of electromagnetic brake

When the three-phase asynchronous motor needs to be braked, the current of the electromagnet is controlled to make the electromagnet generate a large electromagnetic force. The electromagnetic force acts on the rotor of the motor, causing the motor speed to decrease rapidly, thus achieving the purpose of braking.

4.2 Application scenarios of electromagnetic braking

Electromagnetic braking is suitable for occasions where rapid braking is required and high braking effect is required, such as elevators, cranes, etc. In these occasions, the motor needs to stop running in a short time and the braking effect is required to be stable and reliable.

1. in conclusion

There are many braking methods for three-phase asynchronous motors, and different braking methods are suitable for different application scenarios. When selecting a braking method, it is necessary to comprehensively consider factors such as the type of motor, operating conditions, and braking requirements. Dynamic braking, reverse braking, regenerative braking, and electromagnetic braking are common braking methods, each of which has different characteristics and application scenarios.