AC Single-Phase Motors

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Single-phase motors arc used frequently in large and small industries. They are especially useful in applications where motors of less than 1 horsepower are required and in locations where a motor is required and three-phase voltage is not available. In these applications the single-phase motor can be installed on the single-phase voltage source and produce the required horsepower.

The single-phase motor uses a theory of operation that is similar to that of the three-phase motor. There are several minor changes in the single-phase motor design to achieve the same function as a three-phase motor. These changes include the addition of several components and the modification of several others. Fig. 1 (above) shows a picture of a typical single-phase motor. It's important to note at this time that a single-phase voltage source may consist of L1 and L2 for 208 and 230 volt systems, or L1 and neutral for a 115 volt system.

A typical single-phase motor.
Above: Fig. 1: A typical single-phase motor.
Three Phase Synchronous Motors

Single-Phase Motor Components