CHAPTER IV 



FIELD COMPOUNDING TESTS AND 

 MAXIMUM OUTPUT TESTS 



Field Compounding 



Field compounding tests determine the additional 

 ampere turns field necessary to overcome armature 

 reaction and CR drop in a machine from no load to 

 full load. The test is made by separately exciting the 

 field of the machine under test, in order to hold the 

 voltage at the armature terminals constant as the load 

 is increased from no load to full load. Readings of 

 amperes field, volts field, amperes armature, volts 

 armature, and speed are taken at no load and at least 

 three intermediate points between no load and rated 

 load. It is generally required and usually advisable 

 to take an observation at 25 per cent overload, if the 

 power is available. All readings should be made with 

 a rising field current. On polyphase apparatus the 

 phases should be loaded equally so that their currents 

 will be properly balanced. Fig. 10 shows a curve of 

 field compounding in which amperes field or ampere 

 turns are plotted as ordinates and amperes armature 

 as abscissae. This curve is plotted to the values given 

 in Table V. 



TABLE V 



Field Compounding on a 150 Kw., 250 Volt, 225 R.P.M., 

 6-Pole, D-C. Generator 



(6 Bar Brush Shift) 



[33] 



