Pacific service magazine . that a trolleywire has fallen and theline has become short-circuited, or grounded,and that the machine isin danger of burning out. On the oc-currence of the short circuit, the currentflow increases rapidly to an excessiveamount. For an instant this excessive cur-rent does not prove dangerous, as fre-quently when two or more large trainsstart at the same time the instantaneouscurrent is excessive, but should it continuefor more than a fraction of a minute theapparatus would be damaged. To preventthis, an electric relay opens the switchesconnecting the machine to the l
Pacific service magazine . that a trolleywire has fallen and theline has become short-circuited, or grounded,and that the machine isin danger of burning out. On the oc-currence of the short circuit, the currentflow increases rapidly to an excessiveamount. For an instant this excessive cur-rent does not prove dangerous, as fre-quently when two or more large trainsstart at the same time the instantaneouscurrent is excessive, but should it continuefor more than a fraction of a minute theapparatus would be damaged. To preventthis, an electric relay opens the switchesconnecting the machine to the line and thusprotects it from destruction. After a fewseconds to allow the short circuit to clearitself, if possible, the switch is automaticallythrown in again, feeling out to deter-mine if it can be closed with safety. Ifthe line is clear, the switch will stay inand the operation will continue as , should the line still be short-circuited the switch will feel out againand again, continuing this process until. Motor generator automatic switchboard and supervisory controlledrailway feeder at Station E, Piedmont. the line is clear and the switch remainsclosed. In addition to being protected againstshort-circuits and grounds on the lines, themotor-generator sets are automatically pro-tected against many other classes of acci-dents. Should the voltage on the line fur-nishing alternating current power to thestation drop below a certain point, thustending to make the machines inoperative,the machines are automatically shut down,but may be started again when the voltagerises to the proper amount. Each time aswitch is opened or a machine is shut downby the automatic equipment the bell alarmsounds in Station L, thus informing theattendant there that the operation at StationE is not normal. Should the bearings on a machine get toohot and be in danger of burning out, athermal relay shuts the machine down anddoes not permit starting again until some Pacific Service Magazine 3
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Keywords: ., bookcentury1900, bookdecade1910, bookidpacificservi, bookyear1912
