The star-delta transformer shown above is excited on the star side with balanced, $$4$$-wire, $$3$$-phase, sinusoidal voltage supply of rated magnitude. The transformer is under no load condition.

With $$S2$$ closed and $$S1$$ open, the current waveform in the delta winding will be

The circuit diagram shows a two-winding, lossless transformer with no leakage flux, excited from a current source, $$i(t)$$, whose waveform is also shown. The transformer has a magnetizing inductance of $$400/\pi \,\,mH.$$

If the waveform of $$i\left( t \right) = 10\sin \left( {100\pi t} \right)A,$$ the peak voltage across $$A$$ and $$B$$ with $$S$$ closed is

The circuit diagram shows a two-winding, lossless transformer with no leakage flux, excited from a current source, $$i(t)$$, whose waveform is also shown. The transformer has a magnetizing inductance of $$400/\pi \,\,mH.$$

The peak voltage across $$A$$ and $$B$$, with $$S$$ open is

The core of two-winding transformer is subjected to a magnetic flux variation as indicated in the figure.

The induced $$emf$$ $$\left( {{e_{rs}}} \right)$$ in the secondary winding as a function of time will be of the form