An elementary book on electricity and magnetism and their applications . parts of the rail and splice bars to be welded complete the sec-ondary circuit. Since the contact between the rail and the bars oneach side is the point of greatest resistance in the secondary circuit,it becomes intensely hot. The current in the welding circuit is about28,000 amperes, and so, after a very short time, the pieces of steelfuse together. An enormous force of about 34 tons is applied to theweld by means of the pressure levers and the ram at the top. Since it is not easy to build ammeters to carry thousands ofa
An elementary book on electricity and magnetism and their applications . parts of the rail and splice bars to be welded complete the sec-ondary circuit. Since the contact between the rail and the bars oneach side is the point of greatest resistance in the secondary circuit,it becomes intensely hot. The current in the welding circuit is about28,000 amperes, and so, after a very short time, the pieces of steelfuse together. An enormous force of about 34 tons is applied to theweld by means of the pressure levers and the ram at the top. Since it is not easy to build ammeters to carry thousands ofamperes, or voltmeters to measure the high voltages now used in long-distance trans-^\ mission, we use instru- ment means of a poten-tial transformer, whichis merely a step-downtransformer with acapacity of only a fewwatts, we may meas-ure the voltage on line with avoltmeter having a range of 125 volts. Such a transformer can-not be used as a step-up transformer and must not be over-loaded. A current transformer (Fig. 263), such as would be. Fig. 263. — Current transformer for mountingon bus bar and plan of connections.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
