482 MAGNETIC CIRCUITS AND TRANSFORMERS
+−V 1 = E 1 Z = jXm(a)+−V 1 = E 1 RC jXm(b)+−V 1 RC jXm(c)R 1 jX 1E 1+
−Figure 11.3.2Equivalent circuits of an iron
core excited by an ac mmf.+−V (^1) R jXm
C
IC Im
R I^0
1 jX 1 jX 2 R 2
E 1
- −
E 2
−
ZL
a : 1
−
V 2
N 1 N 2
(Ideal transformer)
I 1 I 2
Figure 11.3.3Equivalent circuit of a two-winding iron-core transformer as a combination of an ideal
transformer and the nonideal effects.
a Turns ratioN 1 /N 2
E 1 ,E 2 Induced voltage in primary and secondary
V 1 ,V 2 Terminal voltage of primary and secondary
I 1 ,I 2 Input and output current
I 0 No-load primary exciting current
R 1 ,R 2 Winding resistance of primary and secondary
X 1 ,X 2 Leakage reactance of primary and secondary
Im,Xm Magnetizing current and reactance (referred to primary)
IC,RC Current and resistance accounting for core losses (referred to primary)
Y ̄o Exciting admittance (referred to primary), which is the admittance of the parallel
combination ofXmandRC
Z ̄L Load impedance=V ̄ 2 /I ̄ 2