DC separately excited motor commutation circuit

The direction of rotation of a DC motor is determined by the direction of the field field and the direction of the current in the armature winding, and the direction of the field is determined by the direction of the current in the field winding. If the direction of the excitation magnetic field (i.e., coil current) is changed alone or the direction of the armature current is changed alone, the rotation direction of the motor can be changed. The DC separately excited motor commutation circuit is also composed according to the above principles. The circuit is as shown in the figure. In figure (a), switch SA to change the positive and negative wiring at both ends of the excitation coil (winding) L, and the armature at both ends The direction of motor rotation can be changed as long as the polarity of the power supply remains unchanged. In Figure (b), SA is used to change the positive and negative polarity of the power supply at both ends of the armature M, while the polarity of the magnetic coil remains unchanged, and the steering can also be reversible. If the positive and negative polarities of the excitation coil and the armature are changed at the same time, the direction of the magnetic field generated by both will change, so the direction of rotation will not change.