94 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



current voltage to the direct-current voltage. Assume that the 

 coil pitch is one and that the phase spread is one-third. 



10. In problem 6 calculate the ratio of the twelve-phase alter- 

 nating-current voltage to the direct-current voltage. Assume 

 that the coil pitch is one and that the phase spread is one-sixth. 



11. The graph representing the flux density in the air-gap of 

 a rotary converter is a simple harmonic function. Assume that 

 the armature winding is uniformly distributed. Calculate the 

 ratio of the single-phase alternating-current voltage to the 

 direct-current voltage. Assume that the coil pitch and the 

 phase spread are eaah unity. 



12. In problem 11 calculate the ratio of the four-phase alter- 

 nating-current voltage to the direct-current voltage. Assume 

 that the coil pitch is one and that the phase spread is one-half. 



13. In problem 11 calculate the ratio of the three-phase alter- 

 nating-current voltage to the direct-current voltage. Assume 

 that the coil pitch is one and that the phase spread is two-thirds. 



14. In problem 11 calculate the ratio of the six-phase alter- 

 nating-current voltage to the direct-current voltage. Assume 

 that the coil pitch is one and that the phase spread is one-third. 



15. In problem 11 calculate the ratio of the twelve-phase alter- 

 nating-current voltage to the direct-current voltage. Assume 

 that the coil pitch is one and that the phase spread is one-sixth. 



16. The graph representing the flux distribution in the air- 

 gap of a rotary converter is B = Bisinx + # 3 sin 3x. x is the 

 angular displacement measured from the neutral point. Take 

 the third harmonic component of the flux density as 0.3 of the 

 fundamental. Assume that the armature winding is uniformly 

 distributed. Calculate the ratio of the single-phase alternating- 

 current voltage to the direct-current voltage. Assume that the 

 coil pitch and the phase spread are each unity. 



17. In problem 16 calculate the ratio of the four-phase alter- 

 nating-current voltage to the direct-current voltage. Assume 

 that the coil pitch is one and that the phase spread is one-half. 



18. In problem 16 calculate the ratio of the three-phase alter- 

 nating-current voltage to the direct-current voltage. Assume 

 that the coil pitch is one and that the phase spread is two-thirds. 



19. In problem 16 calculate the ratio of the six-phase alter- 

 nating-current voltage to the direct-current voltage. Assume 

 that the coil pitch is one and that the phase spread is one-third. 



20. In problem 16 calculate the ratio of the twelve-phase 



