File:The Street railway journal (1902) (14758637481).jpg

Identifier: streetrailwayjo191902newy (find matches)
Title: The Street railway journal
Year: 1884 (1880s)
Authors:
Subjects: Street-railroads Electric railroads Transportation
Publisher: New York : McGraw Pub. Co.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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sured length of level track, keeping an accuraterecord of the current input and voltage per motor at each in-stant. Then let this sample run be repeated successively for aperiod of 10 Ik mi s, or long enough for the motor temperatures tohave reached their maximum, and we have the relation betweenenergy lost in the motor and its temperature for a given set ofconditions. Vary the length of the test run and repeat the 10-hour test, and we have another relation between temperaturerise and energy loss for another set of conditions. It is evidentthat a series of such tests taken on a given type of motor wouldgive material from which the relation between its internal losses £< 320028002400200016001200800400 Volts Spe ed K _ Amp ! 1 es 600550500 the motor during its cycle of operation. If necessary, an auto-matic device for applying the current could be used, such as amotor to throw on the controller at a pre-determined speed.Sufficiently good results can be obtained, however, by ordinary
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FIG. 5 hand control with a trained operator, while sample runs taken;every few minutes by recording instruments serve as a checkand furnish the material upon which to base the motors perform-ance during the test. A sample set of curves of such a test is shown in Fig. 4 indicat-ing voltage, amperes and speed upon a time basis, all taken byrecording instruments. The voltage indicated is that between-third-rail and ground, but the motor voltage during running uponresistance may be taken as proportional to its full internalvoltage at the moment of cutting out final starting resistance,without making any appreciable error in arriving at iron lossvalues. The ampere curves give the means of determining thecopper losses by plotting on polar co-ordinates as in Fig. 5, anddetermining the area by planimeter, giving directly the squareroot ofmean square value. Both Fig. 4 and Fig. 5 show curvesproduced by a recording instrument placed directly in the maincircuit of the car. thus giving the series

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