
Passive components 21
£B = -L állát = -Ν άΦΙώ, and all of the flux Φ
links both windings, it follows that the ratio of
secondary voltage E, to the primary back EMF
Ep B
is equal to the turns ratio:
E, _ /Vs
(1.7)
If a resistive load R is now connected to the
secondary, a current EJR will flow, since Es
appears to the load like a source of EMF. By
itself,
this current would produce a large flux in the core.
However, the flux cannot change, since the resul-
tant primary back EMF
Ep «
must balance the fixed
applied EMF
E „
(see Figure 1.10b and c). Conse-
quently an additional current /p flows in the
primary to provide an MMF which cancels out th ...