PROPERTIES OF IDEAL TRANSFORMER & PHASOR DIAGRAM
PROPERTIES OF AN IDEAL TRANSFORMER.
Ideal transformer is an imaginary transformer which has following properties:
1. Primary and secondary winding of an ideal transformer has negligible resistance.
2. The core of an ideal transformer has infinite permeability so negligible mmf is required to setup the flux in the core.
3. The entire flux produced in the ideal transformer is confined only to the core and links with the two windings only. Hence, its leakage flux and leakage inductance is zero.
4. There are no losses in the transformer due to resistance , hysteresis and eddy current.
Thus, the efficiency of an ideal transformer is 100%.
Practical transformer does not have such properties.
PHASOR DIAGRAM OF AN IDEAL TRANSFORMER AT NO LOAD.
Given figure shows the phasor diagram of an ideal transformer.
Since the transformer is on no load, so the current in the secondary winding is zero i.e. I2 = 0
Here ,V1 = Primary Supply Voltage.
E1 = Primary Induced Emf.
I1 = Primary Current.
Ø = Mutual flux.
V2 = Secondary Output Voltage.
E2 = Secondary Induced Emf.
Since the ideal transformer has zero impedance of primary and secondary winding,so voltage induced in the primary winding E1 is equal to the applied voltage V1. But by LENZ’S LAW, E1 is equal and opposite to the V1.
The current I1 drawn from the supply is sufficient to produce an alternating flux Ø in the core. This current is also called magnetizing current because it magnetizes the core and sets up flux in the core.
So, the current I1 and flux Ø are in the same phase.
Primary current I1 lags behind the supply voltage V1 by 90 degree.
Since emf induced in primary winding E1 and secondary winding E2 are induced by the same mutual flux, Ø . So, E1 and E2 are in same direction.
Since the ideal transformer has zero impedance of secondary winding so emf induced in secondary winding E2 and secondary output voltage V2 will be equal in magnitude and in same direction.