Electrical Machine - IES Academy
Electrical Machine - IES Academy
Electrical Machine - IES Academy
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India’s No. 1<br />
<strong>IES</strong> <strong>Academy</strong><br />
Transformer<br />
Chapter-1<br />
0.696 × 300<br />
ηmax<br />
= = 96.2%<br />
0.696 × 300 + 4.12 + 4.12<br />
GATE-5. Ans. (d)<br />
E1 N1<br />
4<br />
GATE-6. Ans. (d) = =<br />
E2 N2<br />
2<br />
E1 E1 N1<br />
4<br />
E<br />
2<br />
= = 200 V and = =<br />
2 E3 N3<br />
1<br />
⇒ E<br />
3= 100 V<br />
E2<br />
200<br />
I<br />
2<br />
= = = 20A<br />
R 10<br />
100 -100<br />
⎡∵<br />
2<br />
I<br />
3<br />
= = =j 40 j=-1<br />
-jx<br />
c<br />
j2.5 ⎣<br />
Now,I<br />
2<br />
refered to primaryside i.e. I<br />
1''<br />
I'<br />
1<br />
N2<br />
2 20<br />
= = ⇒ I<br />
1' = = 10A<br />
I2 N1<br />
4 2<br />
∴ I<br />
1' = 10A<br />
Now,I3 refered to primaryside i.e. I<br />
1''<br />
I''<br />
1<br />
N3<br />
1<br />
= = ⇒ I<br />
1<br />
'' = -j10A<br />
(-I3)<br />
N1<br />
4<br />
- ve sign is taken to consider coil current direction I<br />
3.<br />
Hence, I<br />
1<br />
= I'<br />
1<br />
+ I''=10<br />
1<br />
− j 10 A<br />
GATE-7. Ans. (a) Induced emf in secondary = -N<br />
2djφ<br />
dt<br />
During − 0< t < 1<br />
dφ<br />
E<br />
1= − =−0.12V<br />
dt<br />
E1and E2are in oppsition<br />
E<br />
2= 2E<br />
1=0.24 V<br />
During 1 < t < 2<br />
d φ/dt = 0, then E1 = E2<br />
= 0<br />
During 2 < t < 2.5<br />
dφ<br />
E<br />
1=<br />
− = 0.24 V<br />
dt<br />
Then E<br />
2<br />
= − 0.48V<br />
dl 400 ⎡ 10 ⎤ 800<br />
GATE-8. Ans. (d) V = M = M ×(slope of I vs t ch) = × 10 − 3 × volts<br />
dt π<br />
⎢<br />
=<br />
5 10 3<br />
⎥<br />
⎣ × − ⎦ π<br />
⎤<br />
⎦<br />
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