Short-circuit braking of brushed DC motors

Following the rotation principle and power generation principle of brushed DC motor, we will introduce the short-circuit braking of brushed DC motor in this article. Because this is also one of the series of working principles of brushed DC motor, please understand it together.

Brushed DC motor short circuit braking

For brushed DC motors, the brushes can be shorted to apply the brake, quickly stopping the inertial spinning rotor after power is turned off.

With the brushes disconnected from power and the coil (rotor) still rotating in the counterclockwise direction, short-circuit the brushes.

In the state of ①, as described in the previous power generation principle, the left brush generates a (+) electromotive force relative to the right brush, so current flows due to the brush short circuit. As a result, the outside of coil A becomes N, and the outsides of coils B and C become S.

After transitioning to state ②, current also flows, the outside of coil B becomes S, and the outsides of coil A and coil C become N.

When the brushes of a brushed DC motor are short-circuited in this way, a rotational force (solid black arrow) is generated in the opposite direction of the current rotation, and this becomes a braking action that stops the original rotation. This is called "short-circuit braking."

As the current of the brushed DC motor increases, the force to stop the rotation increases, so when the brushed DC motor speed is high, a stronger brake will be applied; when the brushed DC motor speed decreases, the brake will become weaker, and when the brushed DC motor rotation stops, the brake will become zero.

Key Takeaways:

・By short-circuiting the brushes, a rotational force in the opposite direction can be generated, and a braking effect can be obtained to stop the rotation.