. Electrical world. transformers, resistances or other regulat-ing devices and confines the current to the motors themselves, andas these are below the car floor the danger from the current is re-duced to the minimum. At the same time the air cylinders, in addition to performing all thefunctions of speed control, give to the machine the independent unitelement, and the ability to store the kinetic energy of the train instopping and utilizing it in starting. On account of these and otherfeatures the electric motors of this system can be much smaller incapacity when rated as continuous working m
. Electrical world. transformers, resistances or other regulat-ing devices and confines the current to the motors themselves, andas these are below the car floor the danger from the current is re-duced to the minimum. At the same time the air cylinders, in addition to performing all thefunctions of speed control, give to the machine the independent unitelement, and the ability to store the kinetic energy of the train instopping and utilizing it in starting. On account of these and otherfeatures the electric motors of this system can be much smaller incapacity when rated as continuous working motors, than those ofother systems not possessing this equalizing load feature, and thecapacity of the power house and line can be reduced to about one-halfof what would be required with systems where the fluctuating start-ing loads of the cars are transmitted back to the power house. In order to better understand the diflferent operations of the sys-tem, Fig. 4, showing a speed diagram, has been prepared, in FIG. 4.—DIAGR.\MMATIC OF OPERATION. on the axis of abscisse, O U L, are represented the different carspeeds in per cent of the synchronous motor speed, while the co-ordinate axis, A O B, represents the rotor and stator speeds corre-sponding to the car speeds shown. The operation of the car may be divided into the following periods: I. STANDING IN THE STATION. Referring to Fig. 3 the rotor R is standing still, while the stator 5runs wifh full synchronous speed. The stator is then transferringthe full energy of the electric motor through crank C to the com-pressor cylinder 5 C, which energy is being delivered in form ofcompressed air into the air reservoir. Since the relative velocity between the stator and the rotor is,under all conditions of operation, constant, the speed curves of statorand rotor may be represented by two parallel lines, OCR and A DS in Fig. 4. The origin O of the given co-ordinate system representsthe period of rest of the car, an
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectelectri, bookyear1883
