Reversed Supply Polarity in a Separately Excited DC Motor

When the supply polarity to the armature terminals of a separately excited DC motor is reversed, the motor operates under the plugging condition. This means that the motor experiences a sudden reversal in its direction of rotation and comes to an abrupt stop.

Explanation:

1. Separately Excited DC Motor:
- A separately excited DC motor is a type of DC motor where the field winding is supplied from a separate source, independent of the armature winding.
- The field winding creates a magnetic field that interacts with the armature winding to produce torque and rotation.

2. Supply Polarity Reversal:
- In a separately excited DC motor, the armature terminals are connected to the DC power supply.
- The DC power supply provides a direct current to the armature winding, creating a magnetic field that interacts with the field winding to produce rotation.
- Reversing the supply polarity means changing the direction of the current flow through the armature winding.

3. Plugging Condition:
- Plugging is a method of stopping a DC motor by reversing the polarity of the armature terminals while the motor is still rotating.
- When the supply polarity is reversed, the armature current changes direction, causing the motor to experience a sudden reversal in torque.
- This sudden change in torque opposes the existing rotational motion and brings the motor to a quick stop.

4. Regenerative Braking and Dynamic Braking:
- Regenerative braking and dynamic braking are methods of decelerating a motor by converting the kinetic energy of the rotating motor into electrical energy.
- These methods are typically used in situations where the motor is required to slow down or stop gradually.
- Reversing the supply polarity in a separately excited DC motor does not result in regenerative braking or dynamic braking. Instead, it causes the motor to stop abruptly under the plugging condition.

5. Normal Motoring Condition:
- In a normal motoring condition, the supply polarity to the armature terminals is set in such a way that the current flows in the desired direction to produce the desired rotation.
- Reversing the supply polarity disrupts the normal functioning of the motor and leads to the plugging condition.

Therefore, when the supply polarity to the armature terminals of a separately excited DC motor is reversed, the motor will run under the plugging condition, experiencing a sudden reversal in its direction of rotation and coming to an abrupt stop.