In the case of sudden stopping of DC motors, sudden stop switch or relays are used. In case of a sudden stop, the voltage induced in the industry is added to the line voltage. To limit this current, instantaneous stop resistor is used in circuit (Rf). The value of the instantaneous stop resistance (rf) equals approximately the (Ry) resistor resistor. To automatically perform a sudden stop, a switch that is automatically operated in the circuit is used. This key marked with the letter (A) works with the friction force or centrifugal force on the shaft.
In order to ensure high starting torque, the shunt winding in the circuit is continuously kept connected to the mains. When the start button is pressed in this circuit, contactor (M) is energized. The contact (M) contact seals the start button and ensures continuous operation. The contacts in the power circuit (M) are closed. The cable is connected to the mains. A current passes through the lube from top to bottom. The motor rotates in the direction shown. Due to the friction or centrifugal force in the shaft, the (A) sudden stop switch closes. Normally the closed (M) contact is switched on before the contactor G is not energized. The motor operation continues until the stop button is pressed.
When the stop button is pressed, the current of the (M) contactor is cut off and the inductor is disconnected from the mains. The previously opened (M) contact closes. (A) The sudden stop switch remains closed because the inertia is rotating due to the inertia. The contactor G is therefore energized. The contacts (G) are closed and the armature is connected to the mains again. In this case, a current passes from the endogenous to the upper. This current creates a rotational torque in the reverse direction. The rotational speed of the rotating end of the arrow decreases rapidly. When the speed is zero, the (A) sudden stop switch is turned on. The (G) contactor is de-energized. The contacts (G) are opened and the inductor is disconnected from the mains. The motor is stopped in a very short time, without turning in the opposite direction.