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TARE Marine REVIEw 27 44 to 81 are used by the power company, and, although only partly installed, the plan covers the whole installation so far as the switchboard, generators, transmission, etc., are con- cerned. As power is rented, the installation progresses. The generators installed at present were supplied by the Stanley Electric Manufacturing Co., of Pittsfield, Mass. They were represented on the ground by Mr. E. O. Sessions. Three-phase, 30-cycle, 2,400-volt, 180-R.P.M. revolving-field generators with 95 percent efficiency and 7 percent regulation are used, excited at 220 volts. Three 400-Kw., direct-current, 600-volt, compound-wound (with adjustable shunt from I percent to Io percent over- compound) generators supply current for the street railway. 'Lhe base, pedestal, shaft, coupling, etc., of these direct-current generators are interchangeable with those of the alternating- current generators... [The exciter units are 100-Kw., syn- chronous motor-generators with 2,400-volt revolving-field motors and 220-volt compound exciting generators. The motor-generators ordinarily are started from the direct-cur- rent end with 3-step resistance in the armature circuit. A 100-Kw.-hour storage battery is also provided to regulate the exciter circuit and supply exciting current if the exciters are shut down for any reason. The switchboard arrangements are the most novel features of the plant, as the whole of the starting, stopping or regulat- ing of all units is done at the switchboard by one man, as well as the manipulation of all the switching apparatus. To accomplish this, only pilot and indicating circuits are brought to the operating switchboard, all the regular rheostats, oil switches, etc., being located near the generators themselves. The power units are divided for switchboard purposes into three sections and each section provided with an upper and lower set of bus-bars. The circuits are distributed along the bus-bars, as far as possible joining them at the same points as the generator leads, so that practically the bus serves only to carry the cross or equalizing current and hold the units in synchronism instead of transmitting the whole amount of power. The sections are tied together ordinarily by oil cir- cuit breakers so that only one section would be affected by an accident or short circuit. Ordinarily, half of each section is on the upper and half on the lower bus, making practically six sections. Three oil switches for each generator and feeder are so arranged that two operate as selector switches to either the upper or lower bus before the remaining one is thrown. Two switches are always in series on the circuit and both open together when the circuit is interrupted either automatically or from the switchboard. All the oil switches are solenoid operated of the type that hold in by the action of the solenoid and release whenever the solenoid current is interrupted. Switches in the pilot circuit are provided at the generator and oil switches, so that, in case of accident or inspection, the oil switches can be open from any point and their control taken automatically from the switchboard. This is in a line with automatic block- signal practice, in which any failure of electric circuits is on the side of safety and it is an excellent idea to carry out in switchboard design. Beginning at the top of each panel of the operating switchboard, there is a short panel, devoted to one outgoing feeder, with ammeters of the edgewise type in each leg of the three-phase circuit. At one side of these three instrument dials is the pilot switch - controlling the main-feeder switch. This control switch, when thrown up, connects its feeder to one set of bus-bars and, when thrown down, to the other set. Energiz- ing the solenoid will close the circuit breaker, but this will immediately open again in case there is a short circuit. In case the pilot-cireuit switch is closed in such a position as to close the main circuit breaker, and the circuit breaker is open, a green lamp is lighted below the pilot switch on the board. This green lamp is lighted as long as the circuit breaker is open and the pilot switch closed. If the pilot switch is open, the circuit breaker will necessarily be open and the green lamp will not be lighted. Immediately below the feeder panel are two generator panels. Beginning at the top, each generator panel has an indicating wattmeter, at the side of which is the double- throw pilot switch, controlling the solenoids of the main operating switch and circuit breaker, which is of the same type as that just described for the feeders. Next below this is an edgewise ammeter, in one leg of the generator circuit, at one side of which is a voltmeter switch. This voltmeter switch is for the purpose of connecting the generator to a voltmeter located elsewhere on the switchboard. There are two voltmeters on the board, one of which is permanently connected to the bus-bars, and the other one used only when a generator is being started up. The voltmeter switch will spring back to off position as soon as the attendant lets go of it. Next below the generator ammeter on the board is an edgewise ammeter in the field circuit of the generator. This ammeter has beside it a switch by which the attendant at the board can regulate the speed of the water wheel driving the generator and can also start or stop the wheel. The principle of this control is very simple. A small direct-cur- rent motor is attached to the Lombard water-wheel governor so as to change the relative opening of the gates at a given tension of the governor balls. By rotating the motor in one direction the gates are opened wider with the governor balls in a certain tension and, by rotating it in the other direction, the reverse action takes place. In starting up and increasing the speed, the attendant holds in the switch, which will cause this motor to revolve to open the gates wider. The motor will run to open the gates as long as the attendant holds the switch closed, but the switch will open as soon as the attend- ant lets go of it. The attendant can, therefore, bring the machine into exact synchronism without leaving the switch- board. One very important feature of the way this switchboard is arranged is the facility with which the attendant can note any variation in the load carried by the several machines in operation. The dials of all the indicating wattmeters and ammeters being very close, side by side, like instruments being in the same horizontal plane and provided with scales of similar dimensions, it is easy to note the relative position of the pointers on the same kind of instruments clear around the switchboard. To facilitate this, the pointers are made broad and tapered to a point at one end for accurate reading of the scale. When the load is equal on all the generators, the wattmeter needles should show a continuous unbroken band around the length of the switchboard and a variation on any instrument is easily noted by the break which it would cause in the line. The same thing will hold true with the ammeters in the field circuits of each generator. If the current in the field circuit of each generator is the same, the only thing which could cause a variation to the load, taken by the different generators, would be a lack of. sufficient gate opening on the turbines to hold a generator fully up to synchronism, or the reyerse. In order to make the gen- erator take its share of the load, the attendant would only have to hold his speed-regulating switch up, so as to rotate the synchronizing motor for a few seconds, to change the governor adjustment and give a greater gate opening on the turbine driving that generator. The com- pactness and completeness of this switchboard commend themselves to every electrical engineer who has had to do with the switchboards of large power stations. On each generator is an emergency switch, as it is called, by which a man on the generator-room floor can open all the circuits leading to any generator in case of trouble. When this emergency switch is open, a red