Operating Alternators or AC Generators in Parallel

Pointers for Operating Alternators in Parallel:
1) If the load of a single generator becomes too large that its rating is exceeded, it is necessary to add another generator in parallel to increase the power available from the power station. Before attempting to connect AC generator in parallel, the following conditions must be met:

Three Phase Synchronous Motor

Figure 1: Cutaway view of  an eight pole, 2000 horsepower synchronous motor.

Introduction:
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.

Polyphase Induction Motors

Figure 1: A typical three phase motor.