What defines an asynchronous motor?

An asynchronous motor is characterized by operating at a speed that is slower than its synchronous speed. This deviation from synchronous speed occurs due to the presence of slip, which is the difference between the synchronous speed of the magnetic field in the stator and the actual speed of the rotor. This slip is essential for the motor to generate torque and is a fundamental principle of induction motors.

In contrast, synchronous motors run at their exact synchronous speed and do not experience slip under normal operation, which is why that choice does not accurately define an asynchronous motor. Asynchronous motors can run on alternating current, making them unsuitable to be defined only as functioning with direct current. While they can be used in mechanical applications, this characteristic alone does not define them but rather describes one of their potential uses. Thus, the defining feature of an asynchronous motor is its operation at a speed slower than synchronous speed, emphasizing the critical aspect of slip involved in their function.