QUESTIONS AND I'HnHLEMS 



md attracted during the other half-cycle? What are the approximate 



efliciencv and maximum capacity of this type of device? 



5. What property hits aluminum, when immersed in a It solutions, 

 which make- it possible to utilize it in the rectification of alternati: . 



Sketch a wiring diagram of such a rectifier which rectifies every 

 le. What are the disadvantages and the limits of capacity for this 



>T? 



6. What common methods may be used to convert alternating; to direct 

 current on a large scale? Name the disadvantages of each type f apparatus. 



7. Name the machines whose principles are embodied in the synchronous 

 converter. Just how is the converter armature connected? How i^ power 

 supplied to the. ordinary converter armature? What power is taken from 

 the armature? Name the different types of familiar machines for which 

 the converter may be used. 



8. Under what operating conditions is the synchronous converter called 

 direct"? "Inverted"? 



9. Indicate the points at which the slip-ring taps connect to the winding 

 in a four-phase, two-pole converter. Four-phase, four-pole con ver 



10. Repeat (9) for a three-phase, two-pole converter and a three-phase, 

 four-pole converter. How many taps will an eight-jNile. six-phase converter 

 have? What special restriction, not necessary with the ordinary direct 

 current winding, is imposed on the converter winding? Why? 



11. Compare the numlxjr of active conductors between brushes with the 

 numl>er between sharing taps in the single-phase converter. llo\\ is 



-ulting voltage between direct-current brushes obtained? IV 

 sli|>-ring taps? What is the relation between the t\\o? 



12. Show by a circle and an inscribed polygon how the individual in- 



voltages of a converter add. Indicate how; (a) the single-phase volt- 

 age is obtained; (l,\ the three-phase voltage; (c) the four-phase voltML'e: 

 (d) the six-phase voltage. 



13. Knowing the . lations in a converter armature, derive tin- 

 ratio of the direct current to the alternating current |*-r terminal 



irle-phase converter. (/M the three-phase converter. < the four-phase 

 converter; </ the six-phase c< ct of efficiency and 



power-factor on these ratios. 



14. Sketch the variation of the direct current in a single conductor midway 



![>-ring taps, as it takes successive positions in its rotation 

 Sketch the alternating current in this same conduct. riding 



>it is in phase \\ith the induced emf. I md the 

 resultant current. 



15. Repeat I 1 for a conductor iip-rinir t 



16. Refloat (15) for n i- rabl> lev. than , M . 



17. What is the effect on t he resultant current cur\- Q| increMfaf the 

 number of phases? 



18. Whv of phases materially In 



' \\ i (1 



rapidly \\ith u decrease i:. ."c in most other typee of 



apparatus? 



