220 COMMERCIAL ELECTRICAL TESTING 



be changed to the next tap. On very large compensators 

 it is often necessary to wait several hours between heat 

 runs, otherwise the compensator will run hot and smoke. 

 The heat run at normal rating cannot always be taken 

 on all legs at the same time on account of insufficient 

 power. In such cases run at reduced current and increased 

 time or bare the Y connection, short circuiting the tap to 

 the Y. 



On compensators not standard, or those covered by 

 special instructions, the impedance volts should be 

 measured. See that frequency is correct for this test. 

 When the heat runs have been finished, inspect the oil 

 boxes for leaks; if they are tight, empty the oil out and 

 turn them upside down to drain. Connrci inside 1 motor 

 leads to the second lowest tap, replace the oil boxes, 

 tape and insulate all the connections, and replace the 

 covers. All cast iron oil boxes are tested for leaks by 

 filling with oil for ten hours. Pressed steel boxes are 

 tested before delivery to the testing department and 

 therefore need not be removed from the compensator. 

 Insulation Test 



Double potential should always be applied after the 

 compensator has been completely assembled and the 

 taps insulated with tape. Double voltage is applied to 

 the line terminals for one minute, the frequency being 

 high in order to keep the magnetizing current below the 

 normal current of the compensator. 



If the compensator is designed for high voltage, double 

 potential may be applied on the taps for one minute. 

 The high potential test is made in the usual way, with 

 all leads connected together. Compensators up to and 

 including 600 volts are tested at 2500 volts. 



ROTARY CONVERTER REACTANCES 



Reactances are generally used in compounding rotary 

 converters. They are placed between the secondary of 

 the step-down transformer and the collector rings of the 

 rotary. 



The ratio of conversion of rotary converters, except 

 those of the split pole type, is practically constant for all 

 field strengths. Therefore, to increase the continuous 



