Electric braking is a method of stopping or slowing down a DC motor by using its own generated electromotive force (EMF) to counteract the applied voltage. Shunt DC motors are one type of DC motor that can be effectively braked using this technique.
Shunt DC motors have a field winding (shunt field) in parallel with the armature winding. When the armature rotates, it generates a back EMF due to Faraday's law of electromagnetic induction. This back EMF opposes the applied voltage, and the motor speed is controlled by the balance between the applied voltage and the back EMF.
During electric braking of a shunt DC motor, the armature circuit is opened, disconnecting the motor from the power supply. However, the field circuit remains connected. As a result, the motor continues to rotate due to its inertia. The armature windings continue to rotate within the magnetic field of the shunt field winding, generating a back EMF.
The generated back EMF now acts as a voltage source, but in a direction that opposes the original motion of the motor. This back EMF causes a current to flow in the armature circuit in a direction opposite to the original current flow during normal operation. This current produces a braking torque that opposes the motion of the motor, causing it to slow down and eventually come to a stop.
The effectiveness of electric braking in a shunt motor depends on various factors, such as the strength of the shunt field, the initial speed of the motor, and the load attached to the motor. It's important to note that electric braking might not bring the motor to an immediate stop; it will gradually slow down the motor until it comes to rest.
Electric braking is a regenerative process in which the kinetic energy of the rotating motor is converted back into electrical energy. This can be useful for energy efficiency in certain applications, as the recovered energy can be dissipated as heat or fed back into the power supply.
In industrial and practical applications, electric braking of shunt DC motors can be achieved through various methods, including dynamic braking and plugging. Dynamic braking involves using external resistors to dissipate the generated back EMF, while plugging involves reversing the voltage polarity applied to the motor to bring it to a stop more quickly.
It's important to implement electric braking carefully to avoid overheating of components and to ensure the safety of the motor and the surrounding equipment. Proper control systems and circuitry are often used to manage the braking process effectively.