What is one disadvantage of using a series wound DC motor?

A series wound DC motor connects its field windings in series with the armature. This configuration allows for high torque at low speeds, making the motor capable of accelerating under load. However, the drawback lies in its speed regulation. As the load on the motor varies, the armature current changes, which in turn affects the field strength and the speed of the motor. When under higher loads, the armature current increases, reducing the speed due to increased magnetic flux. Conversely, under lighter loads, the speed can increase dramatically. This results in poor speed regulation, making it less ideal for applications requiring consistent speed across varying loads.

In comparison, the other options present characteristics that do not accurately reflect the nature of series wound DC motors. For instance, they may not require complex control systems to operate effectively, and while efficiency can vary, it is not solely dependent on the low-speed operation of this motor type.