Change The Rotation Direction Of DC Motor

There are two methods to change the rotation direction of DC motor:

One is the armature reverse connection method, that is, keep the polarity of the terminal voltage of the excitation winding unchanged, and reverse the motor by changing the polarity of the terminal voltage of the armature winding.

The second is the reverse connection method of the excitation winding, that is, the polarity of the armature winding terminal voltage is kept unchanged, and the direction of the motor is adjusted by changing the polarity of the excitation winding terminal voltage. When both voltage polarities change at the same time, the rotation direction of the motor will not change.

The armature reverse connection method is generally used to realize the forward and reverse rotation of separately excited and parallel excited DC motors. The reason why it is not suitable to use the reverse connection method of excitation winding to realize forward and reverse rotation for separately excited and parallel excited DC motors is that the number of turns of excitation winding is large and the inductance is large. When the excitation winding is reversed, a large induced electromotive force will be generated in the excitation winding. This will damage the insulation between the knife switch and the excitation winding.

The reason why series excited DC motor should adopt the reverse connection method of excitation winding to realize forward and reverse rotation is that the voltage at both ends of armature of series excited DC motor is high, while the voltage at both ends of excitation winding is very low, so it is easy to reverse connection. This method is often used in electric locomotive.