50 Dr. McLachlan on Effective Inductance, Effective 



nearly constant. This is again attributable to eddy currents 

 and to the effect of the air-gaps. A similar curve is obtained 

 in testing an iron circuit completely wound and without air- 

 gaps. In this latter case the power factor of iron sheets of the 



Fig. 11. — Curves showing variation in primary effective resistance, under 

 different conditions, with frequency. 



300 



250 



5 200 



! 50 



P3 100 



Id 



m 50 













V 



..-''" 











/a'X 



**■ 









• 













s 



S 





(D 







/ * 



/*' 



) 











-A 



/a 















5x!G 3 



20 

 per 



25 



30 



35x10' 



second. 



10 15 



Frequency - 



Curve 1 = Effective Resistance of Primary with iron unpolarized, 

 i. e. magnet removed after full advance. Coil with brass 

 end-plates, and in housing. 



Curve 2 = As in Curve 1 but with magnet in place, i. e. iron polarized. 



Curve 3 = Effective Resistance with armature removed from housing. 



Intercept on vertical axis = res. of primary at zero frequency =0 55 w. 



same thickness as those in the magneto is greater at 10,000 ~ 

 than that in fig, 13. The power factor of the primary winding 

 cannot be considered as " small." Its magnitude is due to 

 (1) the increase in loss and (2) the decrease in inductance 

 with frequency. The use of thin sheets of iron of high 

 permeability, high resistivity, and low hysteresis loss would 

 improve matters considerably. 



