REGULATORS 211 



under load; if humming is noticed during the core loss 

 test, the cable lugs connecting the two secondary circuits 

 in multiple should be removed to see if the noise is caused 

 by exchange current. 



Fig. 73 shows the connection for the heat run on two 

 IRH regulators. 



When the heat run is finished, measure all hot resist- 

 ances and finish the test as on transformers. In using 

 high potential between the secondary windings, a very 

 high charging current is necessary on account of the large 

 electrostatic capacity. The damper of the air-blast 

 regulator should be inspected for proper operation. Oil 

 cooled regulators should be inspected for leaks and pres- 

 sure test should be made on the cooling coils of water 

 cooled regulators. 



Switch Type (BR) Regulator 



Modern central stations employ alternating current 

 generators of large capacity, each generator usually sup- 

 plying two or more districts through independent feeders. 

 One feeder may serve a business district, while another 

 from the same generator may feed a residential district. 

 As the voltage regulation required on any of the feeders 

 depends on the amount of load carried by the feeder, 

 and as the load peak occurs at different times in different 

 feeders, a device to regulate the feeder voltages inde- 

 pendently is necessary. 



Induction regulators may be used, but the automatic 

 BR feeder regulator has been expressly designed for this 

 work. Fig. 74 shows the circuits of this regulator. 



The automatic BR feeder regulator can change the 

 line voltage quicker and with a smaller power consump- 

 tion than any other automatic type. The only moving 

 part is a small, light switch arm. The friction of a 

 number of small switch contacts constitutes the only 

 resistance to turning. 



The moving part of the switch carries a series of fingers 

 the majority of which are always in contact. (See Fig. 75.) 

 Each finger is connected to a stationary collector ring by 

 a brush, and the collector ring is connected to the line 



