Fig. step 13.8 . A beneficial transformer having a loaded additional: (a) new magnetized circuit, a good schematic drawing of your own transformer; (b) the electronic similar circuit.

The primary current has two components. One is the magnetizing current i_{Yardseterseters} (the current that flows in the primary when no current flows in the secondary). The other is i?_{1} the component resulting from the flow of current in the secondary. Therefore,

Since could well be questioned the benefit input off an ideal transformer is the same as the advantage returns since there are no loss.

where R?_{L} is the apparent resistance ‘seen looking into the primary’ as a result of connecting R_{L} to the secondary. It is perhaps more useful to express it as

## During the an ideal transformer, the flux is the identical in both windings (assumption (2) above) therefore the mmfs produced by both windings can be assumed getting equivalent and you can oppose one another

In practice, the flux in the two windings is not exactly the same, and assumption (2) for the ideal transformer does not strictly apply to the practical one. As shown in Figure 13.9(a) , some of the flux ‘leaks’ out of the core and is linked to only one of the windings. It is shown in the description of the circuit of Figure 13.9(a) that the effect of this leakage flux is to induce a voltage which opposes the input voltage. This effect is represented in the equivalent circuit by an inductor. The revised equivalent circuit of the transformer therefore includes the two inductors L_{1} and L_{2} to account for the leakage inductance of the two windings. The equivalent circuit is shown in Figure 13.9(b) .

Fig. thirteen.nine . An excellent transformer which have a jam-packed supplementary indicating the new leakages flux and the new ensuing inductance: (a) the brand new magnetized circuit demonstrating the brand new leakage flux; (b) brand new electricity similar routine.

The equivalent circuit shown in Figure 13.9(b) is more commonly used in its simplified form. The simplification is done in two steps. First, assume that the voltage drop in R_{1} and L_{1} due to the magnetizing current i?_{M} is negligible. Therefore, L_{M} can be connected directly across the source on the other side of R_{1} and L_{1} without the introduction of any error. The component R_{M} is added to represent the loss of energy in the core caused by the alternating magnetic flux. The second step makes use of Eqn () . This allows the secondary resistance and leakage inductance to be combined with the primary ones. The resistor R_{2} is seen at the primary as R?_{2} and this can be combined with R_{1} to form R_{W} as

Figure 13.5(a) shows a coil, or winding, of N_{1} turns wound on a meetville magnetic core. The coil is connected to a d.c. source of voltage V_{1}. The current I_{1} is determined by the resistance of the coil R_{1} as indicated by the equivalent circuit shown in Figure 13.5(b) . The magnetic flux induced by the current I_{1} is determined as follows (see also Hughes, 1995 ; R. J. Smith, 1984 ; Slemon and Straughen, 1980 ).

Figure 13.8(a) shows a transformer with a load R_{L} connected to the secondary winding. As a result of the voltage v_{2} induced in the secondary, a current, i_{2} flows around the secondary circuit. However, this current flowing in the secondary winding creates an mmf which, according to Lenz’s law, opposes the flux in the core which induced v_{2} in the first place. Thus, the net mmf in the magnetic circuit is reduced and this in turn reduces the flux?. According to Eqn (13.5) , the reduced flux leads to a reduction in the voltage induced in the primary which opposes the input voltage v_{1}. The increased difference between the two leads to an increase in the current i_{1} until a new state of equilibrium is achieved. Therefore, an increase in the current in the secondary leads to an increase in the current in the primary.