Ans. Lack of sensitiveness.
Ques. Which is the accepted lamp method, dark or brilliant?
Ans. In the United States it is usual to make the connections for a dark lamp at synchronism, while in England the opposite practice obtains.
With the dark lamp method, the breaking of a filament might cause the machines to be connected with a great phase difference, whereas, with the brilliant lamp it is difficult to determine the point of maximum brilliancy. This latter method, therefore may be called the safer.
Ques. What may be used in place of lamps for synchronizing?
Ans. Some form of synchroscopes, or synchronizers.
Ques. How does the Lincoln synchronizer work?
Ans. The construction is such that a hand moves around a dial so that the angle between the hand and the vertical is always the phase angle between the two sources of electric pressure to which the synchronizer is connected.
If the incoming alternator be running too slow, the hand deflects in one direction, if too fast, in the other direction. When the hand shows no deflection, that is, when it stands vertical, the machines are in phase. A complete revolution of the hand indicates a gain or loss of one cycle in the frequency of the incoming machine, as referred to the bus bars.
Cutting Out Alternator.—When it is desired to cut out of circuit an alternator running in parallel with others, the method of procedure is as follows: