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room, in two separate compartments divided by a watertight bulkhead' and arranged so that, in the event of either dynamo room. being flooded with water, the ship could still be lighted from the unflooded side. A better arrangement for the gen- erators would have been to place them nearer the center of the ship, but be- ing a vulnerable part, the admiralty required them to be placed below the water line, hence the reason for placing them so far aft. MAIN SWITCHBOARD, To control this great power with safety and efficiency in a confined space exposed to a high temperature and possible 'trouble from vibration, required controlling switch gear of a substantial design, yet sensitive in ac- tion. The main switchboard is divid- ed into two parts, one section being erected in the port generating room and the other in the starboard gener- ating room. Each board has two generator pan- els, 12 feeder panels, and one discon- necting panel. Normally the two switchboards are connected together as one board through the disconnect- ing switches, but may be separated in a moment from either room, and each side of the ship operated as a sepa- rate installation. The use of fuses for the control of the large currents dealt with, would have been inconvenient and _ unsafe, and instead automatic circuit breakers (performing the function of both switch and fuse) were fitted. These circuit breakers are of mas- sive construction, the contact surfaces being pressed firmly together by lev- ers. The make-and-break contacts are massive carbon 'blocks, at the extrem- ity of the switch arms, and the main circuit breakers are so arranged that the flash at breaking takes place in fireproof compartments well clear of the attendant. To accomplish this ob- ject and to make the operation of the switches easy, the handles are placed below and connected to the switches by insulating links behind 'the board. These switches are held in the closed position by engaging with a trigger which may be released either by hand or by a trip coil. In order to prevent the opening of the circuit breakers during a momen- tary overload, a relay is introduced which closes the trip coil circuit when an overload occurs, after a period ad- justable up 'to 15 seconds. Should, however, a reversal of current through the generator take place, the relay Promptly closes the trip coil circuit, and thus cuts the machine out of cir- "TAE 7/\ARINE. REVIEW cuit. The opening of the « circuit breaker in turn breaks athe ftip coil circuit, and prevents damage to the coil or waste of energy. The feeder switches are operated in a similar way, but without the reverse current arrangement. They have, how- ever, in addition, a trip coil in series with the main current, adjusted to open the circuit with a greater current than the' relay is set to operate at, but. instantaneous: in. action. Thus, should a short circuit or heavy over- load occur and the relay fail to op- erate, damage to the cables and ma- chinery is effectively prevented. The rélay is simple and reliable in operation, "It consists ofa small. mo- 'tor, similar to that used in meters, through which part of the current is shunted. This motor tends to wind a strong silk cord onto a drum against the pull of a weight fastened to the Gther end of the cord. The cord passes round a drum to which the contact arms are fitted. When the current exceeds the overload limit, the torque of the motor is sufficient to wind up the cord, and thus close the trip coil scircuits. The adjustments are affected by altering the weights and varying the distance between the contacts. All the ammeters and voltmeters are of the moving coil type, the former being operated from shunts in the Main. circtuts. By this. méans. it: ts possible to have the reading instru- ments in any convenient place, and in the Mauretania two instruments are fitted for each machine, one béing in the port and one in the starboard room. On each board, one additional ammeter is fitted, connected to bars behind the feeder panels, and so ar- ranged that it may be connected by a plug to any one circuit at a time. By this means the current in any feeder may be: ascertained without the ex- pense of separate instruments for each circuit. Two station voltmeters and two paralleling voltmeters are provid- ed, and the shunt regulators, which are placed behind the boards, are op- erated by a hand wheel on the front. MAIN CABLES. ' The Cunard company, with their usual precautions for the comfort 'and safety of their passengers, decided that a high voltage would not be advisable, which accounts for the current being generated at only 110 volts. This ne- cessitated cables of a great carrying capacity, and also very heavy switch gear. The admiralty further required all main cables to be run under the water line, and to accomplish this it was' necessary to utilize the only available 33 spaces in the coal bunkers or through the 'boiler rooms. Those who ,have had experience in the lighting of ships will know that these spaces generally are most objectionable for electric wires, especially the coal bunkers. The high temperature of the boiler room, and the very large cables ne- cessitated special precautions being taken to prevent the heat softening the insulation and allowing the cable to sink through the rubber, causing a short circuit. With ordinary armored and lead-sheathed cables, the heat would readily effect the insulating materials. It was, therefore, neces-' sary to adopt fire-resisting covering as well.as the usual vulcanized rub- ber, so that in addition there is a heat- resisting compound and an outer cov- ering of two coats of asbestos braid fitted on the cables. The double-wire system is used throughout, and there are 48 main cables of about 2 in. external diameter running from the generating station to the various sections of the ship. The power is divided into 24 sub- stations of approximately 100 H. P. each, 12 of these being on the port side of the ship and 12 on the star- 'board side. Eight of these stations provide power for forced-draft fans, two to supply the engine ro6m ma- chinery, and.two for engine room lighting, the remaining 12 being con- nected to auxiliary switchboards at convenient distributing centers throughout the ship. AUXILIARY SWITCHBOARDS, These 12 auxiliary switchboards are placed 'directly opposite each other, port and starboard, and cross connect- ing. cables. are fitted so that, in the event of one section failing, the supply can be maintained from the other side. It should be mentioned here that, as. the motors are only used intermittent- ly, there is always sufficient surplus carrying capacity in the cables to pro- vide for emergencies of this nature, thus guarding against any total ex-. tinction of the light. The auxiliary switchboards are fit- ted in fireproof chambers, principally ion the main deck. The switches are single pole, and the fuses double pole --Mr. Lackie's patent zinc fuse--which breaks circuit with a minimum flash. Each board is provided with a spare panel containing spare fuses ready at 'a moment's notice. BRANCH CABLES AND WIRES, From these auxiliary switchboards, vulcanized rubber cables are carried in wood casings to section fuse boxes, which again provide distributing boxes at convenient positions for supplying