Manual for submarine mining

by United States. War Department

In the fourth receptacle, voltage of storage battery.

With the A. C. plug:

In the second receptacle, voltage of A. C. power on the busses is indicated.

In the third receptacle, voltage of external A. C. power, if the latter is supplied.

In general, no external A. C. power should be led into the casemate, as the system would be unsafe, owing to the liability of a “cross.” The standard system is perfectly safe, as it is impossible for a mine to be fired when the motor-generators are idle.

The double circuit breaker is an ordinary single-coil breaker. The single circuit breaker is an overload and reverse-current circuit breaker. The reverse-current coil has two windings, one of which is bridged across the power supply, and the other is in series with it. On charge, the effect of these coils is differential, and on discharge it is cumulative and will trip the circuit breaker when the current from the storage battery exceeds 2 amperes.

Fig. 3.—OPERATING BOARD.

To charge the storage battery:

(a) From an external source of power: Both the single and the double circuit breakers are closed and switch No. 2 is closed to the right (facing the board).