Series-Wound DC Motor (Series-Wound)
A type of DC motor whose field winding is connected in series with the armature. Because the same current feeds both the field and the armature, it produces very high torque at start-up; on the other hand, when the load is removed the speed can rise dangerously. You will meet it in starter motors, winches and some lifting mechanisms.
Torque grows roughly with the square of the current, which is why it excels at lifting heavy loads, but the current also climbs quickly. The current drawn at start-up can reach typically 5–8 times the rated value, and depending on the load this pulse lasts 0.5–3 seconds.
On the driver side, watch two points:
- Sizing: The selection must be made according to the starting pulse, not the average current. If the peak current window of the driver does not cover that pulse, the protection trips or the power stage is stressed.
- Runaway on no load: If the load is removed completely the field weakens and the speed can rise uncontrolled; motors of this type are generally run directly coupled to the load.
Reversing is different too: reversing the supply polarity reverses the field and the armature current together, so the direction does not change. To reverse the direction, only the terminals of either the field or the armature connections must be swapped. For this reason a standard H-bridge output does not give the expected direction behaviour with a series-wound motor.
Where this term is used: DC Motor Driver Selection Guide