Alternate Current Transformer. 5 



d — 



~ "i^(.^io-«iCi) 



due to variation of the primary leakage flux. 



Hence from B draw BC perpendicular to ON and equal to 



wX'ji^(jQt^=x-{ryr^^ say, 



wn^cr 

 where t, = 



CB will fully represent {c). 



From C draw CE perpendicular to OR and equal to wn-^, 

 EC will fully represent {b). 



Join OE. OE will fully represent Ej, the e.m.f. impressed on 

 the primary of the transformer. 



6. At this place attention may be drawn to the importance 

 that will be attached in what follows to the quantities Tj, Tj, 

 and $'. 



As Ti which we will call the numeric of the primary circuit of 

 the transformer or, shortly, the primary numeric, is equal to 



w 



«/ «]^ «!«! 



and ; = —r- 



''i A pA 



I' a, 

 where a^ = sectional area of primary wire 

 /j = mean length of primary turns 

 p = specitic resistance of copper 

 also ar — 4:Tr. permeance of magnetic circuit. We see that tj is 

 equal to Attw into the conductance of the primary wires, considered 

 as one turfi or belt, into the permeance of the magtietic circuit. 



T2 is a similar constant for the secondary circuit, and will 

 generally be nearly equal to tj; we will call it the secondary 

 numeric. In what follows the ratio of Tj to Tj will where 

 necessary be denoted by/ so that 

 Wi" n^a^ 



/-- = — = -^ 



On the other hand & is a variable, varying with the load on 

 the transformer, and for a given load-power-factor approximately 

 as the load. 



