96 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



28. In a three-phase rotary converter assume that the cur- 

 rents on the direct- and alternating-current sides are respec- 

 tively steady and sinusoidal, and neglect all of the losses in 

 calculating their relative values, (a) Calculate the ratio of the 

 average heating in a conductor at one of the alternating-current 

 taps to that in a conductor midway between the taps when the 

 rotary is operating at unit power factor, (b) Calculate this 

 ratio when the rotary is operating at 0.7 power factor. 



29. In a six-phase rotary converter assume that the currents 

 on the direct- and alternating-current sides are respectively 

 steady and sinusoidal, and neglect all of the losses in calculating 

 their relative values, (a) Calculate the ratio of the average 

 heating in a conductor at one of the alternating-current taps to 

 that in a conductor midway between the taps when the rotary 

 is operating at unit power factor, (b) Calculate this ratio 

 when the rotary is operating at 0.7 power factor. 



30. In a twelve-phase rotary converter assume that the cur- 

 rents on the direct- and alternating-current sides are respec- 

 tively steady and sinusoidal, and neglect all of the losses in 

 calculating their relative values, (a) Calculate the ratio of the 

 average heating in a conductor at one of the alternating-current 

 taps to that in a conductor midway between the taps when the 

 rotary is operating at unit power factor, (b) Calculate this 

 ratio when the rotary is operating at 0.7 power factor. 



31. In a single-phase rotary converter assume that the cur- 

 rents on the direct- and alternating-current sides are respec- 

 tively steady and sinusoidal and neglect all of the losses in cal- 

 culating their relative values, (a) Calculate the relative out- 

 puts when operating as a rotary converter at unit power factor 

 and as a direct-current generator on the basis of the same arma- 

 ture copper loss, (b) Calculate the relative outputs when the 

 rotary is operating at 0.7 power factor, (c) Calculate the rela- 

 tive outputs when operating as a rotary converter and as a 

 synchronous generator at unit power factor on the basis of the 

 same armature copper loss, (d) Calculate the relative outputs 

 when both are operating at 0.7 power factor. 



32. In a four-phase rotary converter assume that the currents 

 on the direct- and alternating-current sides are respectively steady 

 and sinusoidal, and neglect all of the losses in calculating their 

 relative values, (a) Calculate the relative outputs when operat- 

 ing as a rotary converter at unit power factor and as a direct- 



