. A text-book of electrical engineering;. Fig- 334 The resultant excitation corresponding to this is seen from Fig. 332 to be 162 amperes, or ,^ ^ A = 162 amperes. The armature demagnetising effect KH = 20 amperes is added geometricallygiving a field excitation BK, where BK = X^ = 176 amperes. Hence, to maintain the terminal at 2200 volts with the lagging arma-ture current, it is necessary to increase the field current to 176 amperes. Onthrowing off the load the will naturally rise to a higher value thanbefore, and Fig. 332 shows this value to be 2520 volts, corresponding to a
. A text-book of electrical engineering;. Fig- 334 The resultant excitation corresponding to this is seen from Fig. 332 to be 162 amperes, or ,^ ^ A = 162 amperes. The armature demagnetising effect KH = 20 amperes is added geometricallygiving a field excitation BK, where BK = X^ = 176 amperes. Hence, to maintain the terminal at 2200 volts with the lagging arma-ture current, it is necessary to increase the field current to 176 amperes. Onthrowing off the load the will naturally rise to a higher value thanbefore, and Fig. 332 shows this value to be 2520 volts, corresponding to afield current of 176 amperes. The rise of the terminal pressure is therefore2520 — 2200 = 320 volts, which is 14-6 per cent, of the normal pressure. The last case which we shall consider is one which is hardly likely tooccur under normal working conditions, viz. cos (f> = o. 320 Electrical Engineering The whole 2200 volts will be used in neutralising the back of theexternal purely inductive load. By adding the internal induct
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