24 



COMMERCIAL ELECTRICAL TESTING 



In making out reports of core loss tests, the following 

 data should be recorded in addition to the electrical 

 readings already mentioned: Circumference of com- 

 mutator; circumference of shunt and series field spools; 

 height of shunt and series field spools; number and 

 width of commutator bars ; size and material of brushes ; 

 number of studs and brushes per stud; brush pressure 

 per brush; rating of driving motor together with its 

 armature and frame number; and the type, rating 



4000 



SOOO 



ZOO 



-4OO 



00 



700 



Fig. 7. 



Short Circuit Core Loss on a 500 Kw., 600 Volt, 20-Pole, 360 R.P.M. 

 3-Phase, 60 Cycle, A-C. Generator 



and number of the machine under test. On series 

 motors core loss tests should be taken at several different 

 speeds covering the range of the speed curve. The 

 method used is identical with that described above, 

 and will be considered in connection with railway and 

 series motor tests. 



Synchronous alternating machines generally have 

 loss measurements taken on open circuit as outlined 

 above, and also with the armature of the machine under 

 test short circuited. In the latter case, the increase in 

 power supplied by the driving motor over that required 



