What is the principal advantage of series-wound DC motors?

The principal advantage of series-wound DC motors is their high starting torque. This characteristic is primarily due to the way the motor is designed; in a series-wound configuration, the field windings are connected in series with the armature windings. Consequently, when the motor starts, the armature current is high, which also results in a strong magnetic field. This strong magnetic field allows the motor to produce a significant amount of torque at startup, making series-wound DC motors particularly effective for applications that require high initial thrust, such as in cranes or electric traction systems.

In contrast, while constant-speed operation or low-speed efficiency might be desirable in certain applications, those features are not typically aligned with the advantages of series-wound motors. Instead, they are better suited for shunt-wound or compound-wound motors, which provide more stable speed characteristics under varying loads. Thus, the high starting torque remains a defining trait of series-wound DC motors, making them suitable for situations where a substantial initial force is required.