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ROTARY CONVERTERS 97 



shifted to give the best commutation over the whole 

 range. 



A set of readings while varying the direct current 

 volts through the total range by means of the auxiliary 

 field, the main field being adjusted to give minimum 

 input for each change in direct current voltage. 



A full load ratio and the current per phase for min- 

 imum input, using main field only. 



Phase Characteristics 



Three full load phase characteristics should be taken 

 as follows : 



1st. Holding the alternating current volts constant 

 and using the main field only. 



2nd. At the lowest limit of the direct current volts: 

 holding the alternating current and direct current volts 

 constant and adjusting the direct current line current 

 to that value which gives the rated output for the mid 

 voltage with zero auxiliary field. 



3rd. At the highest limit of the direct current volts: 

 holding the alternating current and direct current volts 

 constant and adjusting the direct current line current 

 to that value necessary to give the rated output for 

 the mid voltage with zero auxiliary field. 



Core Loss 



Three core loss tests are required to cover the various 

 conditions of operation. These are made as follows: 



1st. Core loss while varying the direct current volts 

 by means of the main field only, with auxiliary field 

 not excited. 



2nd. Core loss while holding the excitation of the 

 main field constant at that value which gives mid 

 direct current voltage, and varying the auxiliary field 

 to change the direct current voltage. 



3rd. Core loss while holding the alternating current 

 volts constant and varying the main field each time 

 the auxiliary field is changed to change the direct 

 current volts throughout the range. This gives unity 

 power-factor. 



All other tests are made as on standard rotaries. 



