Alternate Current Transformer. 53 



L"',=«,/|i + log-|, 

 and if x"\y x"'.2 be the corresponding leakage coefficients 



•^ 1=-^ = — U + log-f. 

 L"., / (, 1) 



Now it is easy to show by means of i-elations already given, 

 that 



where P.2=fu]l load (non-inductive) output, t-=:amp. of current 

 density, p=sp. res. of copper ; so that we have 



ze'Po ( 1 ") 



It will ])e shown, for similar transformers designed on the 



same lines, that t is proportional to v^ZfPa, hence if the e.m.f.s 

 remain fixed, x\ and x" .^ will increase as the square root of the 

 product of output and frequency increases. 



If tlie conductors be rectangular in section instead of circular, 

 the above expressions for x-l" and A",/" will be sufficiently accurate 

 for all practical purposes. 



Note. — The connectors from the ends of either coil to the 

 corresponding ter-minals outside the cases of large transformers 

 ought to include as sninll an area as possible, since on account of 

 the proximity of the ii'on of the transformer and of the case, the 

 loops so formed would have considerable inductance, thus increas 

 ing the leakage coefficients, especially that of the low pressure 

 coil, and so impairing the regulation on inductive loads. 



51. Let us determine the leakage coefficients xp, Xg^ for the 

 transformer designed in Section II. [In this paragraph Xp^ x g^ 

 will be the primary and secondary coefficients respectively, while 

 X2, q.21 etc., will still refer to the coil with the middle section]. 



The details for this transformer are (see §§ 28 et seq.), 



/=!, b=b\ /5=/3', y3=1.151^, /x=2250, 



p=1800, ^=12.9, Ei=3111.10^ E,=311.10«. 



