REGULATORS 215 



The per cent loss and exciting current will be about the 

 same as for a Type H transformer of the same kilowatt 

 capacity. Throw the switch into the other extreme posi- 

 tion and repeat the test. 



Impedance 



Supply current to the primary, with the secondary 

 and iron grid short circuited through an ammeter, the 

 switch being in one extreme position. Increase the 

 primary current until full rated current is obtained on 

 the short circuited secondary, and read amperes, watts 

 and volts primary at the proper frequency. Throw the 

 switch into the other extreme position and repeat the 

 test. Impedance must be taken with the switch in both 

 extreme positions, as in either position only one-half of 

 the secondary winding is short circuited. 



Heat Run 



If two regulators are in test at the same time they 

 may be ' ' pumped back ' ' on each other ; if only one is in 

 test, it may be pumped back on a suitably arranged bank 

 of transformers, or loaded on a water box. In the 

 latter case apply voltage to the primary, connecting the 

 secondary to a water box and adjusting until full load 

 secondary current is obtained. The switch must be in 

 one of the extreme positions. Read and record the tem- 

 perature and also record the temperature of the iron grid 

 resistance. 



Start the test at overload so as to shorten the length of 

 the heat run. Finish as if testing on a transformer. 

 Throw the switch in the other extreme position and run 

 at 50 per cent overload current for one hour to test the 

 other half of the secondary. 



Insulation Tests 



Apply double potential for one minute and one and 

 one-half potential for five minutes. High potential tests 

 on regulators are similar to those made on transformers. 



