In addition to ensuring that the generator frequency matches the frequency of the grid or appliances, the following conditions must also be satisfied:
(a) Output voltage of the generator must match the operating voltage of the grid, or the appliances powered by the generator.
(b) There should be no phase difference between the grid voltage and that of the generator.
In a single-phase generator, the stator has a number of windings connected in series to form a single circuit across which the output voltage is generated.
In a three-phase generator, three single-phase windings are spaced such that there is a phase difference of 120° among the voltages induced in each of the stator windings. The three phases are independent of each other.
Choosing Between Single-Phase and Three-Phase Generators
The output of single-phase generators is usually limited to 25 kVA. At higher ratings, it is less expensive to draw single-phase power supply from a three-phase generator than to buy dedicated single-phase units for higher loads. Read the following article, Tips on Buying Used Generators, to help find the proper generator for any situation.
The choice between a single-phase and a three-phase output is solely dependent on the kind of application to be powered. Single-phase generators are best suited for single-phase output whereas a three-phase generator can easily provide both single- and three-phase power. If all your appliances operate on single-phase power, it makes sense to choose a single-phase generator. If you need to operate appliances that work on different phases, a three-phase generator will serve you best. However, it is essential to account for load balances while stepping up a single-phase generator to a three-phase unit.