Which type of motor operates equally well on AC and DC?

The universal motor is designed to operate effectively on both alternating current (AC) and direct current (DC). This versatility is primarily due to its construction, which includes a series wound armature and field winding. When powered by AC, the universal motor uses the alternating polarity of the current to generate rotation, effectively creating a magnetic field that switches direction in sync with the current. On DC, the motor functions similarly, allowing for consistent torque and speed performance.

Induction motors and synchronous motors, on the other hand, are typically designed for use with a specific type of current. Induction motors require AC for operation, as they rely on the changing magnetic fields generated by AC to induce current in the rotor. Synchronous motors, while also predominantly AC machines, operate on synchronous speed with the supply frequency, which does not allow for efficient operation on DC.

Stepper motors are primarily designed for precise control in digital circuits, usually requiring a specific control mechanism that is not compatible with standard AC or DC configurations. Thus, the universal motor stands out for its ability to run on both types of current, making it suitable for various applications, particularly in household appliances and power tools where variable speed is beneficial.