192 ELECTRIC PROPULSION OF THE U. S. S. JUPITER. 



The character of the apparatus installed in the Jupiter is shown by the ac- 

 companying cuts. It is all of a type commonly used in the electrical industry and 

 need not be described in detail here. There is only one feature about the gener- 

 ating unit which is different from the type of units ordinarily used for electrical 

 purposes, that is, that the governor is so designed that it can be set to hold "any de- 

 sired speed through a wide range, the adjustment of the governor being the nor- 

 mal method of speed variation used in this vessel. The ship can also, if desired, 

 be controlled by the throttle, so that the governor is simply a convenience and in no 

 sense a limitation. 



The windings of the generator, which carry the alternating current, are on 

 the stationary part and are insulated with non-combustible material. The genera- 

 tor drives its own ventilating air by powerful impellers attached to the ends of the 

 rotor. This air is delivered from the top of the generator through a duct which 

 connects to the space from which the fire-room blowers take their air supply. The 

 heated air from the motors also passes out of the engine room through similar 

 ducts. The revolving parts of motors are connected to water-cooled resistances 

 through collector rings, and means are provided by which these collector rings can 

 be short circuited so that the rotor circuits are closed upon themselves. Such a 

 condition, with the resistances cut out, is the normal state of efficient operation, 

 the resistances being used only for the purpose of giving a large torque in revers- 

 ing. The vessel can be operated with the resistances continually in circuit. With 

 this connection, the immediate movement of either motor in either direction is very 

 convenient, and this method of operation is normally used in maneuvering in nar- 

 row waters or about wharves. The ship can, however, be maneuvered and reversed 

 without the use of the resistance, and while this method has not yet been fully ex- 

 perimented with, it is thought that her reversal, even without the resistance, will be 

 about as effective as that of vessels having existing types of equipment. 



Since the Jupiter apparatus was designed, a method of designing induction 

 motors has been developed which will give all the desired characteristics for re- 

 versal without the use of external resistance. Such motors will have squirrel-cage 

 rotors, which are of a simpler character than the definite wound rotors now used. 

 While the method of control and operation of the Jupiter is extremely quick and 

 •simple, the operations necessary with this new type of motor will be simpler still. 

 With this new method it will be extremely easy to accomplish all the operations of 

 speed control or reversal of either propeller from the bridge if desired. 



When the first tests of the Jupiter operation were made she had been lying at 

 the navy yard dock for four months, so that her bottom was in a very foul condi- 

 tion. Her speed in that condition was something like 25 per cent below normal. 

 This produced abnormal electrical conditions, since the low frequency made neces- 

 sary the use of higher magnetic densities than are desirable. Many of the condi- 

 tions of these runs were very unfavorable. A large proportion of the crew were 

 green men ; in one fire-room watch a large proportion of the fire-room force were 

 seasick. A great deal of boiler compound was used in the boilers, and the priming 



