. Electric railway journal . because of the rapidity with which thegate-opening mechanism responds. In placing the gen-erators on the line the action is similar to that ofbringing a synchronous motor up to speed and placingit on full circuit. The ordinary synchronizing processas usually applied to generators does not become a partof the operation in this hydroelectric plant, since plac-ing the machine on the line with low-field excitationallows the rotor to slip back or to be pulled ahead afraction of a phase angle without trouble. Oscillo-graph records of the current in the main generatorcirc
. Electric railway journal . because of the rapidity with which thegate-opening mechanism responds. In placing the gen-erators on the line the action is similar to that ofbringing a synchronous motor up to speed and placingit on full circuit. The ordinary synchronizing processas usually applied to generators does not become a partof the operation in this hydroelectric plant, since plac-ing the machine on the line with low-field excitationallows the rotor to slip back or to be pulled ahead afraction of a phase angle without trouble. Oscillo-graph records of the current in the main generatorcircuit show that the maximum disturbance during thestarting period is not serious. Protection Against Possible Trouble The bearings of each machine are protected againstoverheat by thermostats of the spiral spring type whichare set to operate at 45 deg. C. Should a bearing be-come overheated, the thermostat would promptly actto cut the machine affected off the line. When thebearing cooled down to normal temperature the thermo-. IOWA AUTOMATIC HYDROELECTRIC PLANT—EXCITER CABINET AND MOTOR-OPERATED DRUM CONTROLLER WITH SIDE CASING? OPEN TO SHOW CONSTRUCTION December 1, 1917] ELECTRIC RAILWAY JOURNAL 985 stat would automatically cut the machine in are also placed on the current-limitingreactors and set to operate at 75 deg. C. Thermostatson the stator coils of the generators are set to operateat 65 deg. C. The speed-limiting device already de-scribed is set so that it shuts down the entire plantwhenever the station frequency reaches 64 cycles persecond. In a test of this device the main oil switchat the steam station was tripped from the benchboard,cutting all load off the hydroelectric plant, which, ofcourse, would tend to make the machines run one and two-fifths seconds after the oil switch wastripped, the frequency-limiting device operated andthe water wheel gates began to close. The possibility of a machine operating single-phaseis prevented by the fac
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