What is the effect of armature current in a series-wound DC motor during startup?

In a series-wound DC motor, the armature current plays a critical role during startup due to the design of the motor. A series-wound motor has the armature winding and the field winding connected in series, meaning that the same current flows through both at all times.

When the motor starts, the armature current is initially low because the motor is not yet spinning and generates little back EMF (Electromotive Force). As a result, this low back EMF allows a high armature current to flow, which creates a strong magnetic field due to the series configuration. This strong magnetic field leads to a significant development of torque, which is essential for overcoming inertia and getting the motor up to speed.

The characteristic of producing high starting torque makes series-wound DC motors particularly useful in applications requiring substantial initial power, such as electric traction and cranes. Therefore, the effect of armature current during startup in this type of motor makes it capable of producing the high starting torque necessary for effective operation.