REGULATORS 209 



ance voltage varies from 15 to 20 per cent. This test 

 should be made on three-phase regulators by using three- 

 phase voltage, and on six-phase regulators by using six- 

 phase voltage. Wattmeter readings are not required, as 

 the efficiency is calculated, using the I 2 R losses as com- 

 puted from the resistances. When calculating the full 

 load primary current for this test, assume that the regu- 

 lator operates at a power-factor of 80 per cent. 



In special cases, impedance may be taken from the 

 secondary side, in which event connect the secondaries 

 in Y and apply rated current. An ammeter should be 

 placed in one phase of the short circuited primary. If 

 the primary is permanently connected to the secondary 

 inside the machine, each secondary coil must be short 

 circuited on itself. On all other types, the secondary 

 is short circuited by connecting all the secondary termi- 

 nals on either side with a copper bar. 



A curve should be taken ranging from 50 to 150 per 

 cent full load, with the armature in the maximum boost 

 position. A curve should also be taken while holding 

 full load current and varying the position of the arma- 

 ture. This curve should be very carefully taken over 

 one-half of the segment, to obtain the maximum imped- 

 ance. 



Heat Run 



Whenever possible, heat runs should be made with 

 full load on the regulator, either by pumping one regu- 

 lator back on another, or by pumping back against a 

 bank of transformers. The heat run on two regulators 

 of the same size and type is made by connecting the 

 primaries in multiple through a dynamometer board. 

 One end of the secondary coil of the regulator is con- 

 nected to the end of the secondary coil of the other by 

 short circuiting bars. The other ends of the secondary, 

 coils of one regulator must be in multiple with corres- 

 ponding coils of the other regulator. Normal voltage of 

 the proper phase and frequency is applied to the pri- 

 maries of the two regulators. The handwheel of one 

 regulator must be turned so as to cause sufficient phase 

 displacement of the secondary voltages of the two regu- 



