How can the speed of a DC motor be changed?

The speed of a DC motor can be effectively changed by varying the motor field or armature voltage. This method is rooted in the fundamental operations of a DC motor, where the speed is directly proportional to the voltage applied to the armature. When you increase the armature voltage, it enhances the current flowing through the motor, leading to a higher magnetic field strength and an increase in motor speed. Conversely, decreasing the voltage lowers the speed by reducing the overall power and torque produced in the motor.

Additionally, altering the field voltage—through series or shunt control—can also impact the speed. In a shunt-wound motor, for instance, increasing the field current increases the magnetic field strength, but when balanced with an appropriate armature voltage adjustment, it effectively allows the motor to operate at different speeds.

Modifying the armature winding typically serves other purposes, like changing the characteristics of the motor under load, rather than directly influencing the speed. The mechanical load itself does impact the performance of a motor, but it does not directly change speed through electrical adjustments. Finally, commutator settings are less about speed control and more about ensuring proper electrical contact and minimizing arcing within the motor, which affects performance but not speed regulation.