Three-phase induction motors have three electrical braking methods: energy consumption braking, reverse braking, and regenerative braking.
(1) Cut off the three-phase AC power supply of the motor during dynamic braking, and send the DC power into the stator winding. At the moment the AC power is cut off, the motor still rotates in the original direction due to inertia. This method is characterized by smooth braking, but requires a DC power supply and a high-power motor. The cost of DC equipment required is high, and the braking force is small at low speeds.
(2) Reverse connection braking is divided into load reverse connection braking and power supply reverse connection braking.
1) Load reverse connection braking is also called load reverse connection braking. This torque makes the weight drop slowly at a steady speed. The characteristic of this kind of braking is: the power supply does not need to be reversed, no special braking equipment is needed, and the braking speed can be adjusted, but it is only suitable for winding motors, and the rotor circuit needs to be connected in series with a large resistance to make slip The rate is greater than 1.
2) Reverse power supply braking. When the motor needs to be braked, the two-phase power cord can be arbitrarily adjusted to make the rotating magnetic field opposite to quickly brake. When the motor speed is equal to zero, immediately cut off the power supply. The characteristics of this kind of braking are: fast parking, strong braking force, no need for braking equipment. However, due to the large current and the large impact force during braking, it is easy to overheat the motor or damage the components of the transmission part.
(3) Regenerative braking is also called feedback braking. Under the action of heavy objects (when heavy objects are placed under the crane motor), the speed of the motor is higher than the synchronous speed of the rotating magnetic field. At this time, the rotor conductor generates an induced current, which generates a torque in the reverse rotation direction under the action of the rotating magnetic field, but the motor speed is high, and a transmission device is required to decelerate.
