A transformer is an ac machine that
1. transfers electrical energy from one electric circuit to another
2. does so without a change of frequency
3. does so by the principle of electromagnetic induction
4. has electric circuits that are linked by a common magnetic circuit. The energy transfer usually takes place with a change of voltage, although this is not always necessary. it is a static machine and has high efficiency ( in the range of 96-99%).
A transformer is never operated on dc. If the dc supply is connected to the transformer primary or secondary, it may burn out since there is no self-induced emf and heavy current will flow through it.
Although in the actual construction the two windings are usually wound one over the other, for the sake of simplicity, the figures for analyzing transformer theory show the winding opposite sides of the core.
In an ideal transformer, winding resistance, magnetic leakage, and iron losses are neglected and the core is assumed to have infinite permeability and zero reluctance.
if the transformer is operated with the frequency and voltage changed in the same proportion, the flux density will remain unchanged, and apparently, the no-load current will also remain unaffected.
The transformer can be operated safely at a frequency less than the rated one with correspondingly reduced voltage. In this case, iron losses will be reduced. But if the transformer if operated with increased voltage and frequency in the same proportion, the core losses may increase to an intolerable level. An increase in frequency with constant supply voltage will cause a reduction in hysteresis loss and leave the eddy current losses unaffected. some increase in voltage could, therefore, be tolerated at higher frequencies
1. transfers electrical energy from one electric circuit to another
2. does so without a change of frequency
3. does so by the principle of electromagnetic induction
4. has electric circuits that are linked by a common magnetic circuit. The energy transfer usually takes place with a change of voltage, although this is not always necessary. it is a static machine and has high efficiency ( in the range of 96-99%).
A transformer is never operated on dc. If the dc supply is connected to the transformer primary or secondary, it may burn out since there is no self-induced emf and heavy current will flow through it.
Although in the actual construction the two windings are usually wound one over the other, for the sake of simplicity, the figures for analyzing transformer theory show the winding opposite sides of the core.
IDEAL TRANSFORMER:
In an ideal transformer, winding resistance, magnetic leakage, and iron losses are neglected and the core is assumed to have infinite permeability and zero reluctance.
EFFECTS OF VOLTAGE AND FREQUENCY VARIATION
if the transformer is operated with the frequency and voltage changed in the same proportion, the flux density will remain unchanged, and apparently, the no-load current will also remain unaffected. The transformer can be operated safely at a frequency less than the rated one with correspondingly reduced voltage. In this case, iron losses will be reduced. But if the transformer if operated with increased voltage and frequency in the same proportion, the core losses may increase to an intolerable level. An increase in frequency with constant supply voltage will cause a reduction in hysteresis loss and leave the eddy current losses unaffected. some increase in voltage could, therefore, be tolerated at higher frequencies
