CHAPTER XIV 

 SYNCHRONOUS CONVERTERS 



1. Draw 2 diagrams showing 4-pole, parallel-wound synchro- 

 nous converters for 3 and 4 phases respectively, and show the loca- 

 tion of the brushes and connections to the slip rings on these 

 diagrams. (8 min.) 



2. Construct a table giving in per cent for a direct-current 

 generator and for converters single-phase and 3, 4 and 6-phase, 

 the relation of maximum and effective e.m.f.'s and of the effective 

 alternating currents in the armature windings and in the leads 

 from the brushes. Take the e.m.f. and line current for the direct- 

 current generator as one hundred in each case. (15 min.) 



3. A converter gives 110 volts direct current; determine graphi- 

 cally the maximum e.m.f. between adjacent brushes of the alter- 

 nating-current side if 4-phase, also if 3-phase and 6-phase. From 

 these calculate the effective e.m.f.'s. (8 min.) 



4. In problem 3 if the direct current is 65 amperes and the 

 efficiency 100%, what is the effective single-phase line current? 

 Determine the effective 3, 4 and 6-phase currents in the line. 

 Obtain these values directly by use of the effective e.m.f.'s. (8 

 min.) 



5. Converters are placed upon 2000-volt systems, single, 3, 

 4 and 6-phase. Find the direct-current e.m.f. in each case. 

 (3 min.) 



6. The converters of problem 5 are fed in each case with 250 

 amperes alternating current; determine the direct current in each 

 case. (15 min.) 



7. The converters of problem 5 are each carrying 150 amperes 

 alternating current (sine wave), in the armature conductors; 

 required the alternating line current and the direct current 

 delivered. (9 min.) 



8. A double-current generator is designed to give 230 volts 

 across the outside of a three-wire system. The alternating-current 

 side supplies 3-phase current to step-up transformers. For what 

 e.m.f. must they be designed. If the machine were 4-phase what 



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