Category: SINGLE-PHASE TRANSFORMERS

The losses that occur in an actual transformer are core or iron losses and copper losses. Then, total copper losses  The currents in the primary and secondary winding vary according to the load, and therefore, these losses vary according to the load and are known as variable losses.

The approximate expression for the no-load secondary voltage is derived in Section 16.1. For inductive load   E2 = V2 + I2Res cosɸ2 + I2Xes sinɸ2 or   E2 − V2 = I2Res cosɸ2 + I2Xes sinɸ2 or where, ∴   % Reg = % resistance drop × cos ɸ2 + % reactance drop × sin ɸ2 Similarly (ii) For resistive load: % Reg = % resistance drop (iii) For capacitive load ∴  …

When a transformer is loaded, with a constant supply voltage, the terminal voltage changes due to voltage drop in the internal parameters of the transformer, that is, primary and secondary resistances and inductive reactances. The internal voltage drop also depends upon the load and its power factor. The algebraic difference between the no-load and full-load…

While drawing simplified circuit of a transformer, the exciting circuit (i.e., exciting resistance and exciting reactance) can be omitted. The simplified equivalent circuit of a transformer is drawn by representing all the parameters of the transformer either on the secondary or on the primary side. The no-load current I0 is neglected as its value is very small…

An actual transformer has (i) primary and secondary resistances R1 and R2, (ii) primary and secondary leakage reactance X1 and X2 (iii) iron and copper losses and (iv) exciting resistance R0 and exciting reactance X0. The equivalent circuit of an actual transformer is shown in Figure 10.23. Primary impedance,  = R1 + jX1 Fig. 10.23  Equivalent circuit of an actual transformer on load Supply voltage is V1. The resistance and leakage reactance…

To make the calculations easy, the reactance of the two windings can be transferred to any one side. The reactance from one side to the other is transferred in such a manner that percentage voltage drop remains the same when represented on either side. Let the primary reactance X1 be transferred to the secondary, and the new…

In an actual transformer, the primary and secondary windings have some resistance represented by R1 and R2, respectively. These resistances are shown external to the windings in Figure 10.19. The resistance of the two windings can be transferred to either side in order to simplify the calculations. The resistance is transferred from one side to the other in such…

When a certain load is connected across the secondary, a current I2 flows through it as shown in Figure 10.16. The magnitude of current I2 depends upon terminal voltage V2 and impedance of the load. The phase angle of secondary current I2 with respect to V2 depends upon the nature of load, that is, whether the load is resistive, inductive, or capacitive. (Neglecting winding resistance and…

A transformer is said to be on no-load when secondary winding is open circuited and the secondary current I2 is zero. In this case, neither the secondary winding has any effect on the magnetic flux in the core nor it has any effect on the primary current. In actual transformer, the losses cannot be neglected. Therefore, if…

When sinusoidal voltage is applied to the primary winding of a transformer, a sinusoidal flux, as shown in Figure 10.12 is set up in the iron core which links with primary and secondary winding. Let ɸm = Maximum value of flux in Wb f = supply frequency in Hz (or c/s) N1 = No. of turns in primary N2 = No. of…