32 THE DESIGN OF STATIC TKANSFORMERS 



a sine wave (which has a form factor of 1,11). The effect of 

 assuming a sine-wave curve when the curve will actually be 

 peaked will usually not be detrimental in any respect as 

 regards the performance of the transformer. In fact, it can 

 easily be seen from the precise formula given above, i.e., that 

 involving the use of the form factor, that the flux will be 

 decreased in proportion to the " peakedness " of the pressure 

 curve and consequently the core loss will also be decreased. 

 If the transformer is designed for a high saturation of the core 

 whilst assuming a sine-wave function, then this decrease in 

 the core loss may be quite considerable if the transformer is 

 operated on a peaked pressure-curve. 



The introduction of the form factor in the flux formula, 

 however, is very necessary when the pressure curve is flat, in 

 order that misunderstandings shall not arise between the 

 buyer and the manufacturer should the core loss not corres- 

 pond with the specification. In any case, it would be wise to 

 make more conservative calculations for circuits supplying flat 

 curves than for circuits supplying peaked curves. It may be 

 said, however, that there are few instances in modern generat- 

 ing plants where flat wave forms for the pressure curves are 

 obtained from an alternator, the wave (in cases where there is 

 any departure from the sine form) usually being more or less 

 peaked. The modern tendency is strongly in the direction of 

 specifying that generators shall provide a sine-wave curve of 

 pressure at all loads. The extent of the dependence of the 

 form factor upon the proportions and winding of an alternator 

 is fully discussed at p. 92 of Parshall and Hobart's " Electric 

 Machine Design " (" Engineering," London). 



There can be no object gained by taking the form factor into 

 account in a design such as that with which we are at present 

 dealing, since the application of the form factor to the calcula- 

 tions is of the simplest nature, and, therefore, having no 

 particular supply circuit in mind, we have no reason for 

 assuming other than a sinusoidal pressure. Applying those 



