Single Phase Transformer
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
The efficiency and regulation of a transformer on any load condition and at any power factor condition can be predetermined by indirect loading method.
Single Phase Transformer
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
When the primary winding of a transformer is excited with suitable rated voltage then e.m.f. gets induced in both the windings. The polarities of these e.m.f.s depend on how the windings are wound on the core.
Single Phase Transformer
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
• Due to the losses in a transformer, the output power of a transformer is less than the input power supplied. Power output = Power input - Total losses Power input = Power output + Total losses = Power output +Pi + PCu
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
In a transformer, there exists two types of losses. i) The core gets subjected to an alternating flux, causing core losses. ii) The windings carry currents when transformer is loaded, causing copper losses.
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
• This decrease in the secondary terminal voltage expressed as a fraction of the no load secondary terminal voltage is called regulation of a transformer.
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
• The term equivalent circuit of a machine means the combination of fixed and variable resistances and reactances, which exactly simulates performance and working of the machine.
Single Phase Transformer
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
• Consider a transformer supplying the load as shown in the Fig. 6.12.1.
Solved Example Problems | Single Phase Transformer
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
• The transformer primary has resistance R1 and reactance X1. While the transformer secondary has resistance R2 and reactance X2. Thus we can say that the total impedance of primary winding is Z1
Single Phase Transformer
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
• Uptill now it is assumed that the entire flux produced by the primary links with the secondary winding. But in practice it is not possible. Part of the primary flux as well as the secondary flux completes the path through air and links with the respecting winding only. Such a flux is called leakage flux.
Single Phase Transformer
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
• A practical transformer windings possess some resistances which not only cause the power losses but also the voltage drops. Let us see what is the effect of winding resistances on the performance of the transformer.
Single Phase Transformer
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
When the transformer is loaded, the current I2 flows through the secondary winding. The magnitude and phase of I2 is determined by the load. If load is inductive, I2 lags V2. If load is capacitive, I2 leads V2 while for resistive load, I2 is in phase with V2.
Single Phase Transformer
Subject and UNIT: Electrical Machines: Unit IV: Single Phase Transformer
• Actually in practical transformer iron core causes hysteresis and eddy current losses as it is subjected to alternating flux. While designing the transformer the efforts are made to keep these losses minimum by,