114 COMMERCIAL ELECTRICAL TESTING 



Load is increased by turning the core of the regulator 

 in the direction of boost, the ammeter of machine No. 

 1 being watched at the same time. If the reading 

 reverses from motor load, then No. 1 is running as a 

 rotary; if, however, No. 1 does not reverse, the regulator 

 should be turned in the opposite direction. This shows 

 that the regulator is wrongly connected in reference 

 to its markings; there is no necessity, however, to 

 change connections. 



Using A-C. Loss Supply 



If, instead of supplying the losses from a direct 

 current source of power, an alternator is connected 

 across the alternating current lines, between the inverted 

 rotary and the regulator as in the preceding method, 

 the losses can be supplied at the alternating current 

 end. When the alternator is large enough to start 

 the rotaries, the wiring on the direct current end is 

 greatly simplified. The starting panel is omitted and 

 the shunt fields are connected according to the print 

 of connections for the machine. Load is obtained by 

 means of the regulator as before and the test carried 

 out as already described. 



If the alternator is too small to start the machines, 

 the latter may be started singly from the direct current 

 side as before, and the two phased together. The 

 alternator is then synchronized with the pair. If only 

 one machine can be started by the alternator, bring it 

 up to speed, open all its circuits, and let it run by its 

 own momentum while the second machine is quickly 

 started. The excitation is then removed from the 

 alternator field and the switches on the first machine 

 are closed. Excite the alternator field and bring both 

 machines up to speed together. After the machines 

 are once started, they can be brought up to speed 

 without an excessive current from the alternator. 



