200 COMMERCIAL ELECTRICAL TESTING 



on the first regulator. The other regulator will have 

 full load secondary current and a partially loaded 

 primary; the short circuited winding on the armature 

 accounting for the current not appearing in the primary. 

 Both regulators would generally pass on the results of 

 these heat runs. When special guarantees are required, 

 however, the heat run should be finished on the first 

 regulator, and then the second regulator should be run 

 with the armature in the maximum boost position. 



Overload heat runs are usually taken as a continuation 

 of the normal load heat run. To shorten the heat run, 

 the regulator, if of the air blast type, may be operated 

 for a short while without air; if oil cooled, it may be 

 operated at an overload; while if oil and water cooled, it 

 may be operated for a time without water. Careful 

 inspection should be made for oil leaks and other mechan- 

 ical defects. Hot resistances should be taken in the 

 same manner as on transformers. 



The insulation tests consist of double and high 

 potential tests and are taken in the usual way. Although 

 only a low voltage is induced in the secondary coil, it 

 is in series with the circuit to be controlled, and should, 

 therefore, have the same potential applied as is applied 

 to the primary winding. 

 Operating Motor Tests 



If the regulator is provided with an operating motor 

 and limiting switch, they should be tested during the 

 early part of the heat run so as to avoid rewiring after 

 the heat run is finished. The motor and limiting switch 

 should be connected according to the proper sketch, and 

 readings of the current should be taken at normal 

 potential and frequency, with the motor disconnected 

 from the shaft and with the motor operating the regu- 

 lator in both directions at no load and at full load. 

 When the regulator is under full load, the motor should 

 operate it from one extreme position to the other. To 

 keep load on the regulators while this is being done, the 

 handwheel of only One regulator need be turned. The 

 time required to travel from one end of the segment 

 to the other should be taken and recorded. The limit 

 switch should be adjusted so as to work properly. 



