CHAPTER IV 

 INDUCTION MOTORS 



1. A 2-phase induction motor has a stator with 2 slots per 

 pole per phase. There are 4 inductors in series per slot. The 

 coil pitch is 4 slots. The effective value of the current in each 

 phase of the stator winding is 7.07 amperes, and the current 

 in phase two lags behind the current in phase one by 90 electrical 

 degrees. Place the first slot in phase one at the extreme left 

 of the paper and draw the zero lines to allow for a maximum 

 ordinate of 2 in. Use the following scales in these plots. 



Abscissae Pole pitch = 3 in. 



Ordinates 40 ampere turns = 1 in. 



(a) Plot the distribution of the magnetomotive force in the 

 air-gap due to the stator currents at the time that the current in 

 phase one is a maximum. 



(b) Plot the distribution of magnetomotive force in the air- 

 gap at one-eighth of a period later than in (a). 



(c) Plot the distribution of the magnetomotive force in the 

 air-gap at one-quarter of a period later than in (a). 



2* A 2-phase induction motor has a stator with 4 slots per 

 pole per phase. There are 4 inductors in series per slot. The 

 coil pitch is 8 slots. The effective value of the current in each 

 phase of the stator winding is 7.07 amperes, and the current in 

 phase two lags behind the current in phase one by 90 electrical 

 degrees. Place the first slot in phase one at the extreme left of 

 the paper and draw the zero lines to allow for a maximum or- 

 dinate of 3 in. Use the following scales in this plots: 



Abscissae Pole pitch = 3 in. 



Ordinates 40 ampere turns = 1 in. 



(a) Plot the distribution of the magnetomotive force in the 

 air-gap due to the stator currents at the time that the current in 

 phase one is a maximum. 



Note. Unless otherwise stated assume that the ratio of the turns in the 

 stator and rator windings is the same as the ratio of transformation. 



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