There are three types of DC motors; i.e. series wound, shunt-wound, and compound wound. Since their directions are reversible in a straightforward manner, it is crucial to know what kind of China DC Motor you are working with before you begin.
As the name implies, these DC motors have the armature winding alongside field windings that are internally connected in series. AS a result, both receive the same amount of current. Due to design, the field windings receive more current compared to what they do in other kinds of DC motors.
The high torque produced by these motors is what distinguishes them. Due to their high torque, they are useful as starter motors, often running for only a short period. The series-wound motor, unlike the DC shunt-wound motor, cannot regulate its own speed.
In these DC motors (or DC shunt motors) the manufacturer shunts the field windings (in parallel) to the armature winding. Due to this, the field and armature winding are exposed to the equal supply voltage while part of the current passes through the field winding alongside the other part via the armature winding.
Shunt-wound motors have practically constant magnetic field flux; therefore they are called constant flux motors. Also, they have the capacity to regulate their own speed to make themselves constant.
Compound wound DC motors have both the design of shunt and series wound DC motors. The result you get is excellent speed regulation along with high starting torque. However, the speed is not well regulated compared to the shunt-wound motors. Also, the torque is not as high as series-wound motors.
There are two forms of compound wound DC motors:
A long shunt motor contains the shunt field winding placed in parallel across the series and armature field coil. In this scenario, the speed regulation is better.
A short shunt motor is a bit different. Here, the shunt field winding is placed in parallel across the armature winding only. Besides, the series field coil gets the whole supply current before it gets split into the armature and shunt field currents. Better starting torque is what you get as a result.