SYNCHRONOUS MOTORS 



57 



The resistance of the field circuit is 0.37 ohm. The friction and 

 windage loss is 19.0 kw. The core loss due to rotation is 45.2 

 kw. at 2200 volts and may be assumed constant. The open- 

 and short-circuit characteristics are given by the following data: 



What is the efficiency of this motor when it receives 3200 kw. 

 at 0.80 power factor (a) if the excitation is greater than normal, 

 (b) if the excitation is less than normal? 



Calculate the field current by the magnetomotive-force 

 method. 



13. The following test data are given on a 1340-h.p., 11,000- 

 volt, 3-phase synchronous motor. The armature effective resist- 

 ance is 0.94 ohm per phase, and the resistance of the field winding 

 is 3.11 ohms. The armature windings are connected in Y. 



The friclii.ii and windage 1.. i- 1'J.l h.p. 



\Vh:it i- tin- efiiciencv of thU motor when it receives Us amper.^ 

 per terminal at 11,550 volts if the excitation ifl iirvntiT than 

 normal and i< adjusted so that the power factoris 78.4 per cent.? 



14. The following t.-M .lata an- LMV.-II on a (i.V)O-h.p.. liliOO- 



volt, 3-phase -yn< -hronou- motor. The effective resistance of 



Mre \\indini: ifl D.osl olmi per pha<e. and the nsistance 



of tlie field winding is 0.549 ohm. The armature windings are 



connected in Y. 



