The Wrangell sentinel., 1923-06-28

generators ana exclterS are com. pound wound.
 Current from the two generators is led to a double aramature propul- sion motor unit consisting of two 300 brake horsepower, 130 rpm 230-volt shunt-wound General Elec- tric motors mounted on the same shaft and having common base, from which the tail shaft extends back to the single screw. This is of nine feet three inches diamater with eight feet pitch. It is huilt-up with bronze blades on a cast-iron hub. The exciters are overhung and over sized, and power is drawn from them for running the auxiliary appa- ratus-except the cargo pumps. Use of exciters in connection with direct current generators is necessary be- cause of the Ward Leonard system of control with which the ship is equipped.
 With this installation the en- zines run always in the same direc- tion, irrespective of the vessels progress or maneuvers, and all changes in speed or direction are controlled from the bridge or pilot house by varying the supply of cur rent to the driving motor. Either main Diesel engine will drive the ship at three-quarter speed, mean while operating all necessary aux iliaries for her operation, except. of course, the cargo pumps which nor mally are not in use while the vessel is moving. Either main Diesel en- zine and generator will drive all the cargo pumps.
 The two main generators and the two armatures of the driving motor are connected in series, with one motor armature between the generators in each side of the line. Either motor or generator may be cut out and the circuit at the same time left intact. The exciters are connected through double throw switches to either of two sets of busses, so that the load of the aux iliaries may be distributed to the best advantage.
 An important feature in the cleo trical installation is the absence of any automatic Gircuit-opening de- vices. The field windings of the gen orators are arranged differentially and any excess current in the main line (above that to which the ma chimes are adjusted) will operate to reduce the generator voltage, thus automatically protecting the system from excess strains and at the same time insuring against loss of power at critical moment, as when the control lever is thrown from full ahead to full-astern to avoid collis- ion. The controlling rheostadt of the system by which the ships speed and direction is varied is ;n the engine room, but is operated from the bridge through a distant control. This reduces the amount and size of the apparatus on the bridge and in the pilot house.
 There are two field rheostadts for each generator, and by double pole double = throw switch either can be used. One is for use when the gener- ators are supplying power to the driving motor, and the other is thrown into the circuit when the cargo pumps are being used. In the first condition no adjustment of voltage can be made at the switch board, but in the second the field can be altered as desired. When the second rheostadt is in use the series field of the generator is thrown out of circuit, to prevent a fluctuation of voltage due to heavy starting cur rents. The field switches of the mo- tors are interlocked with the main line switches to prevent inadvert- ent short-circuiting of any motor armature by opening it's field.
 There is fresh water pump built by the Krogh Manufacturing Com pany of San Francisco, and a fire pump supplied by Alberger. of New burg, NY. The sanitary and hot wa ter service-pump unit was also built by the Krogh concern. This unit consists of a motor mounted be- tween two centrifugal pumps, one ot which maintains a supply of wa ter at constant pressure for operat- ing the ships sanitary appliances, and the other maintaining prcula- tion in a water--heating system that utilizes the exhaust-gases from the main oil engines.
 These gases are led through a tu- bular heater, the flow being con- h- l- -a,c o4 xLox