Summary:...
For motors, there are three types of electronic brakes: regenerative braking, dynamic braking, and plugs. In terms of the three methods, the plug provides a quick stop function, but for electronic and mechanical devices, this requirement is very high. For this reason, it is a rarely used brake system, but in some applications, it is very easy.
Plug-in-sometimes called "reverse current braking" is able to use DC or AC motors. For DC motors, plug-in is achieved by reversing the polarity of the armature voltage. When this happens, the back-EMF voltage is not the opposite of the supply voltage. On the contrary, the back-EMF works in the same direction as the supply voltage, contrary to the rotation of the motor and stops it almost immediately. The reverse current produced by the combined supply voltage and electromotive force is very high. Therefore, the current is placed on the circuit to limit the current.
For AC induction motors, the stator voltage is reversed by any two exchanged power leads. The magnetic field rotates in the opposite direction and the motor slip (the difference between the stator magnetic field and the rotor speed) is greater than one. In other words, the rotor is rotating faster than rotating the magnetic field in the stator. The rotor develops in the opposite direction of the motor rotation, which will produce a strong braking effect.
Sliding, which is different from the speed of the stator's rotating magnetic field and the speed of the rotor, is the basic characteristic of AC induction motors. In normal operation, the rotor rotates more slowly, compared to the rotor rotating magnetic field.
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When the motor speed reaches zero, if it is not connected to the power supply, it will reverse or rotate in the opposite direction. In some applications, the rotation of the motor direction is originally a purpose. However, when the plug-in is used to brake the motor, when its speed reaches zero, a zero-speed switch or plug-in contactor is used to disconnect the motor from the power supply.
As a plug-in method of braking, one potential problem is that it is very difficult to brake the motor at zero speed. Another drawback of plug-in is that it may cause high mechanical shock loads on the motor due to its sudden stop. Plug-in is a very inefficient method to stop, and, therefore, this will generate a huge amount of heat.
Despite these reasons, plug-in power is used in equipment such as elevators, elevators, cranes, machine tools, etc. In these fields, the rapid stop of the motor is necessary.
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