Ques. How is the voltage of an incoming machine adjusted so that it will be the same as the one already in operation?
Ans. By varying the field excitation with a rheostat in the alternator field circuit.
Ques. How may two or more alternators be started simultaneously?
Ans. After bringing each of them up to its proper speed so as to obtain equal frequencies, the main switches may be closed, thereby joining their armature circuits in parallel. As yet, however, their respective field windings have not been supplied with current, so that no harm can result in doing this. The exciters of these machines after being joined in parallel, should then be made to send direct current simultaneously through the field windings of the alternators, and from this stage on the directions previously given may be followed in detail.
Ques. What are the conditions when two or more alternators are directly connected together?
Ans. If rigidly connected together, or directly connected to the same engine, they must necessarily run in the same manner at all times.
When machines connected in this way are once properly adjusted so that they are in phase with each other, their operation in parallel is even a simpler task than when they are all started together but are not directly connected.
Ques. When an alternator is driven by a gas engine, what provision is sometimes made to insure successful operation in parallel?
Ans. An amortisseur winding is provided to counteract the tendency to "hunting."