Because of the nature of AC voltage and current, the operation of an AC generator requires that rules and procedures be followed. In addition, there are various types of AC generators available, each type having advantages and disadvantages.

EO 1.5DESCRIBE the bases behind the kW and current ratings of an AC generator.

EO 1.6DESCRIBE the conditions that must be met prior to paralleling two AC generators including consequences of not meeting these conditions.

EO 1.7DESCRIBE the difference between a stationary field, rotating armature AC generator and a rotating field, stationary armature AC generator.

EO 1.8EXPLAIN the differences between a wye-connected and delta-connected AC generator including advantages and disadvantages of each type.

Ratings

Typical name plate data for an AC generator (Figure 4) includes: (1) manufacturer; (2) serial number and type number; (3) speed (rpm), number of poles, frequency of output, number of phases, and maximum supply voltage; (4) capacity rating in KVA and kW at a specified power factor and maximum output voltage; (5) armature and field current per phase; and (6) maximum temperature rise.

Power (kW) ratings of an AC generator are based on the ability of the prime mover to overcome generator losses and the ability of the machine to dissipate the internally generated heat. The current rating of an AC generator is based on the insulation rating of the machine.

Figure 4 AC Generator Nameplate Ratings