Resistance, and Self- Capacity of Magneto Windings. 71 



the peak voltage and the -damping attain maximum values, 

 but these occur at the same value of the added inductance. 

 In the absence of wave forms, it is impossible to explain 

 the phenomenon folly; but there is a similarity between the 

 results and those of fig. 17. 



It appears, therefore, that when the phase relation of the 

 two oscillations is such that the peak voltage is a maximum 

 the effect on the iron of the core is to magnetize it in 

 such a way that the damping is a maximum. Although 

 the peak voltage is increased, it will be found that the 

 conversion efficiency is practically the same with an added 

 inductance of 2'2 millihenries as it is without this inductance. 

 Similar curves were obtained with the armature in the 

 housing, but the damping was much higher. By increasing 

 the inductance sufficiently, more than one peak was obtained. 



Oneof the most important factors in ignition with a sparking- 

 plug is the " rate of rise of voltage/' Although the peak 

 voltage for a given current is augmented by adding uncoupled 

 inductance to the primary, it does not follow that this would 

 be beneficial, since it is possible that it would cause a 

 reduction in the rate of rise of voltage. Dr. Campbell has 

 shown that, apart from the foregoing consideration, it would 

 be impracticable to add uncoupled inductance to the primary 

 of a magneto*. 



General Conclusions en Losses. 



(1) The evidence with regard to iron loss caused by 

 hysteresis and eddy-currents is such that its occurrence 

 reduces the efficiency of the magneto considerably. 



(2) The reduction in the effective permeability of the 

 magnetic circuit caused (a) by air-gaps, (//) by the screening 

 effect of eddy currents, (c) by polarization due to the magnet 

 especially at retard break, gives rise to an appreciable drop 

 in peak voltage. 



(3) Apart from modifications arising from alteration in 

 the coefficient of coupling of the two circuits, the detri- 

 mental effects commented on in (1) and (2) can be partially 

 remedied by the use of thin laminations of the form specified 

 at the beginning of the paper. 



(12) Self-Resonance of Secondary Winding. 



Owino- to the large effective inductance and self-capacity 

 of the secondary coil, its first resonance occurs at a fre- 

 quency well within the acoustic range. Two methods of 



* Loc at. 



