Electrical Machine - IES Academy
Electrical Machine - IES Academy Electrical Machine - IES Academy
India’s No. 1 IES Academy Transformer Chapter-1 0.696 × 300 ηmax = = 96.2% 0.696 × 300 + 4.12 + 4.12 GATE-5. Ans. (d) E1 N1 4 GATE-6. Ans. (d) = = E2 N2 2 E1 E1 N1 4 E 2 = = 200 V and = = 2 E3 N3 1 ⇒ E 3= 100 V E2 200 I 2 = = = 20A R 10 100 -100 ⎡∵ 2 I 3 = = =j 40 j=-1 -jx c j2.5 ⎣ Now,I 2 refered to primaryside i.e. I 1'' I' 1 N2 2 20 = = ⇒ I 1' = = 10A I2 N1 4 2 ∴ I 1' = 10A Now,I3 refered to primaryside i.e. I 1'' I'' 1 N3 1 = = ⇒ I 1 '' = -j10A (-I3) N1 4 - ve sign is taken to consider coil current direction I 3. Hence, I 1 = I' 1 + I''=10 1 − j 10 A GATE-7. Ans. (a) Induced emf in secondary = -N 2djφ dt During − 0< t < 1 dφ E 1= − =−0.12V dt E1and E2are in oppsition E 2= 2E 1=0.24 V During 1 < t < 2 d φ/dt = 0, then E1 = E2 = 0 During 2 < t < 2.5 dφ E 1= − = 0.24 V dt Then E 2 = − 0.48V dl 400 ⎡ 10 ⎤ 800 GATE-8. Ans. (d) V = M = M ×(slope of I vs t ch) = × 10 − 3 × volts dt π ⎢ = 5 10 3 ⎥ ⎣ × − ⎦ π ⎤ ⎦ www.iesacademy.com E-mail: iesacademy@yahoo.com Page-48 25, 1 st Floor, Jia Sarai, Near IIT. New Delhi-16 Ph: 011-26537570, 9810958290
India’s No. 1 IES Academy Transformer Chapter-1 GATE-9. Ans. (d) dl ⎛400 ⎞dl V = L = dt ⎜ π ⎟ ⎝ ⎠dt dl is Ma dt if m ∝ → 5 m sec 4ω 10 ⎡800⎤ V= × V π 5 ⎢ π ⎥ ⎣ ⎦ i(t) = 10 sin (100 πt) 400 d V = × i(t) π dt 400 V = ×π×10cos (100 πt) π V = 400 cos (100 πt) V m = 400V GATE-10. Ans. (d) When the switch S1 is open and S2 is closed then V1 N1 11000 = = = 26.50 V2 N2 415 The voltage inducing in phase ‘a’ of Y- winding is opposite to that in phase ‘c’, therefore Vp Vp V ac = − = 0volt 26.5 26.5 GATE-11. Ans. (b) GATE-12. Ans. (b) GATE-13. Ans. (b) Y connection consist 3 rd harmonics in line current due to hysteresis A saturation. GATE-14. Ans. (a) It will be open delta connection and O/P will be sinusoidal at fundamental frequency. 3 50×10 GATE-15. Ans. (d) I 2 = = 217.4A 230 These KVA rating of auto transformer = V0 I 2 = (3530)(217.4)=767.42KVA www.iesacademy.com E-mail: iesacademy@yahoo.com Page-49 25, 1 st Floor, Jia Sarai, Near IIT. New Delhi-16 Ph: 011-26537570, 9810958290
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India’s No. 1<br />
<strong>IES</strong> <strong>Academy</strong><br />
Transformer<br />
Chapter-1<br />
GATE-9. Ans. (d)<br />
dl ⎛400 ⎞dl<br />
V = L =<br />
dt<br />
⎜<br />
π<br />
⎟<br />
⎝ ⎠dt<br />
dl is Ma<br />
dt<br />
if<br />
m<br />
∝ →<br />
5 m sec<br />
4ω 10 ⎡800⎤<br />
V= × V<br />
π 5<br />
⎢<br />
π<br />
⎥<br />
⎣ ⎦<br />
i(t) = 10 sin (100 πt)<br />
400 d<br />
V = × i(t)<br />
π dt<br />
400<br />
V = ×π×10cos (100 πt)<br />
π<br />
V = 400 cos (100 πt)<br />
V<br />
m<br />
= 400V<br />
GATE-10. Ans. (d) When the switch S1 is<br />
open and S2 is closed then<br />
V1 N1<br />
11000<br />
= = = 26.50<br />
V2 N2<br />
415<br />
The voltage inducing in phase ‘a’<br />
of Y- winding is opposite to that<br />
in phase ‘c’, therefore<br />
Vp<br />
Vp<br />
V<br />
ac<br />
= − = 0volt<br />
26.5 26.5<br />
GATE-11. Ans. (b)<br />
GATE-12. Ans. (b)<br />
GATE-13. Ans. (b) Y connection consist 3 rd harmonics in line current due to hysteresis A<br />
saturation.<br />
GATE-14. Ans. (a) It will be open delta connection and O/P will be sinusoidal at fundamental<br />
frequency.<br />
3<br />
50×10<br />
GATE-15. Ans. (d) I<br />
2<br />
= = 217.4A<br />
230<br />
These KVA rating of auto<br />
transformer = V0<br />
I<br />
2<br />
= (3530)(217.4)=767.42KVA<br />
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