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| Figure 1: Cutaway view of an eight pole, 2000 horsepower synchronous motor. |
The synchronous motor is one type of three phase AC motor which operates at a constant speed from no-load to full-load. It is similar in construction to a three phase AC generator but it has a revolving field which must be separately excited from a direct current source. By changing the DC field excitation current, the power factor of this type of motor can be varied over a side range of lagging and leading values. This motor is used in many industry applications because of its fixed speed from no-load to full-load, its high efficiency and to initial cost. It is also used to improve the power factor of three phase AC industrial circuits.
