![GATE EE 2009 Electrical Machines - Transformers Question 21 English](https://imagex.cdn.examgoal.net/HJhQzeEgPV6YpoVxw/XG7cx4VtWOfRaWa9XSDgUAoErEQf7/5KNLOEq61Rtia6ip9Jjkpa/image.png)
The figure above shows coil $$1$$ and $$2,$$ with dot markings as shown, having $$4000$$ and $$6000$$ turns respectively. Both the coils have a rated current of $$25$$ $$A.$$ Coil $$1$$ is excited with single phase, $$400$$ $$V,$$ $$50$$ $$Hz$$ supply.
In the auto-transformer obtained in Question $$30,$$ the current in each coil is
![GATE EE 2009 Electrical Machines - Transformers Question 19 English](https://imagex.cdn.examgoal.net/wCnohx5SMDYlBvzk3/Oezzb2KniivGmpRkwR0zicUZFLXz5/8KuJettRzO8lLAgqprYEI4/image.png)
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 both $$S1$$ and $$S2$$ open, the core flux waveform will be
![GATE EE 2009 Electrical Machines - Transformers Question 18 English](https://imagex.cdn.examgoal.net/wCnohx5SMDYlBvzk3/Oezzb2KniivGmpRkwR0zicUZFLXz5/8KuJettRzO8lLAgqprYEI4/image.png)
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
![GATE EE 2009 Electrical Machines - Transformers Question 16 English 1](https://imagex.cdn.examgoal.net/akTVRmzo9Xdk8XoQI/vNB9FsYvtCvil6qjGvxms7j0CcHEV/N2ZrY9TkjUvsnG3PQt7Kkk/image.png)
![GATE EE 2009 Electrical Machines - Transformers Question 16 English 2](https://imagex.cdn.examgoal.net/4oeDYx1NCdLRRqgWv/bFVoweO4x4BwyzYZrNGzihzgzT74c/rmi7W6Gl6LSY3M1Kg6p2sc/image.png)
The peak voltage across $$A$$ and $$B$$, with $$S$$ open is