Reverse braking control circuit

Reverse braking is to reverse any two of the power lines connected to the motor when it is stopped. Due to the change in the phase sequence of the power supply
, an electromagnetic torque in the opposite direction to the original direction will be generated. The motor still
rotating in the original direction acts as a brake. When the motor speed
approaches zero, the power supply is disconnected. This method has large braking torque and fast braking
, but the braking current is very large. Generally, a resistor must be inserted in series with the stator circuit. The asynchronous motor can perform reverse braking
    after changing its power
phase sequence. When the phase sequence is changed, the rotating magnetic field of the motor stator is reversed,
producing a reverse torque opposite to the original torque of the motor, thus acting as a brake
.
    The reverse braking circuit of asynchronous motor is shown in Figure 4-23. When button SB1 is pressed
, contactor KM1 is closed, causing the motor to drive speed relay
SR - to rotate. After the speed reaches the rated speed, the SR moving contact is closed
and the brake is ready. After pressing the SB2 stop button, Klffl is powered off and
its contact is broken. The SR contact is still
closed under the action of motor inertia. At this time, KM2 is closed and the motor is reversely connected. When the motor speed drops until it stops
, SR is turned off. KM2 is released and braking is completed.