What distinguishes a synchronous motor from an asynchronous motor?

A synchronous motor is distinguished by its ability to run at a constant speed that is directly proportional to the frequency of the electrical supply. This is a fundamental characteristic of synchronous motors; they maintain synchronization with the supply frequency, meaning their rotational speed does not fluctuate under varying load conditions, as long as the motor is adequately powered and not overloaded. This quality allows synchronous motors to provide stable operation, making them ideal for applications requiring precise speed control.

In contrast, asynchronous (or induction) motors do not have this same characteristic. Their speed can vary with load changes, leading to a phenomenon known as slip, where the speed of the motor is slightly less than the synchronous speed dictated by the supply frequency. This difference is due to the way these motors operate, where the rotor must ‘catch up’ to the stator's magnetic field.

Understanding this distinction is crucial for selecting the appropriate motor for specific applications in industries where speed stability is essential.