The asynchronous motor has an electric braking system:

Three phase induction motor electrical braking methods are: energy consumption braking, reverse braking, regenerative braking three.

(1) the three-phase AC power supply of motor is cut off when energy consumption is braked, and the direct current is fed into stator winding. To cut off the AC power of the moment, due to inertia, still according to the original direction of motor rotation, this method features are smooth braking, but high power DC power supply, DC motor, the required equipment cost, low speed small power system.

(2) reverse braking is divided into two types: load reverse braking and power reverse braking.

1) load reverse braking is also called load reverse pull reverse braking. This torque causes the heavy object to slow down at a steady rate. This is the reverse brake: no power, no need to brake equipment, but also can adjust the braking speed, but only suitable for winding motor, the rotor circuit on high resistance, the slip ratio is greater than 1.

2) the power supply reverse braking, when the motor needs to brake, as long as the arbitrary exchange of two phase power line, so that the rotating magnetic field opposite can quickly brake. When the motor speed is zero, the power is cut off immediately. The characteristics of this brake are: quick stop, powerful braking system, no braking equipment. But when braking, because the current is big, the impact force is also big, easy to cause the motor to overheat, or to damage the transmission part's components.

(3) regenerative braking is also called feedback braking. Under the influence of heavy load (when the crane motor moves lower weight), the speed of the motor is higher than the synchronous speed of the rotating magnetic field. At this time, the rotor conductor produces an induced current, which produces a counter rotating torque under the action of a rotating magnetic field, but the motor is rotating at high speed and needs to be decelerated by a gear change device.