TransactionsPublished under the care of the General Secretary and the Treasurer . in reality, they do not complicate matters to any greatextent nor add materially to the cost of a large installation. While, as stated above, the average machine tool may be con-sidered as requiring constant horse-power through its workingrange, in numerous instances, particularly when dealing with large DAT: MOTORS IN MACHINE SHOPS. 607 machinery, we find that requirements call for an increased horse-power with an increase speed. For such cases the multiple-volt-age system is most desirable as is clearly shown b
TransactionsPublished under the care of the General Secretary and the Treasurer . in reality, they do not complicate matters to any greatextent nor add materially to the cost of a large installation. While, as stated above, the average machine tool may be con-sidered as requiring constant horse-power through its workingrange, in numerous instances, particularly when dealing with large DAT: MOTORS IN MACHINE SHOPS. 607 machinery, we find that requirements call for an increased horse-power with an increase speed. For such cases the multiple-volt-age system is most desirable as is clearly shown by the curves inFig. 13. This data relates to a large gun lathe, driven by multiple-voltageapparatus. The lower curves are drawn through points determinedby actual test and show the power required to drive the lathe withface plate in place but otherwise running light. The power avail-able for useful work is represented by the vertical height betweenthe curves just referred to and the upper ones, which show therelation between horse-power and speed of a standard 35-hp Fig. \ 3 9 Face Plate - Data kelative to motor EQriPMEXT for large gtjn lathe SHOWING ADVANTAGE OF A CONSTANT TORQUE SYSTOM. Crocker-Wheeler motor. Such examples are, of course, excep-tional. So far I have assumed the use of the same range in motor speeds,when operating on the spindle, back gear, and triple gear and in thecase of field weakening motors, or those operating on a balancedthree-wire system and rated as above. There would not be any ad-vantage in doing otherwise. The characteristics of the multiple-voltage system, however, are such that a smaller motor can frequentlybe used if the gear ratios are determined by the nature of the loadcurve. This fact was borne in mind when plotting the curves shownin Fig. 14, relative to multiple voltage equipment for lathe A motor weighing 2350 lbs. and operating from 235 608 DAY: MOTORS IN MACHfNE SHOPS. r.
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