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IIT Mandi 2011 B.Tech Electrical Engineering QUIZ 2 of electonics engineering %28ee102%29 at with solutions . - Question Paper

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Ii) Find (he total reluctaocc of the magnetic circuit . _H

' H ** ^,A * ^A'⁵ * 6n.ioKft

HI

121

Ail % C5I2t S. lZL -. a-s p>y\,

p f*!*'**

c) Find the relative permeability of the nianetk material.

-j- ¹ V'C* - m-itytiffitu

S._c tJi, = ** ... , JU1 *3 r a-s

ovo

a* **.* k-*

^C ,/Af V-^,15

**' * ^rx?>7-⁶

d) Find the magnetic Held intensity in the air gap and ihc magnetic material.

12)

H* s ii _ii. - j,_bT,_{3 X(0}*

⁷ J*C V**IO = ^H/

Hxi - rtjtj

5D - V'"*⁵

*V ^77,-^tf ^AT/t

5. Write d'iwn the hvu mesh equations! c* the circuit shown below. |5|

A .> *

iw

s

C +_Jw_l

*hV ->

dl If three capacitors, cach of some capacitance, arc connccted in delta to the same supply so as to form parallel circuit with ihe above ciiits. calculate the capaciiancc of each capacitor to obtain n resultant p.f, of 0.95 taking. |3j

y t * 0.4 <; f-. o as; ₅ nj ij

Uclv(

A| * frij/6 * 3 4 faxAuX a*wa* tA

I -5- - i Ci K\Ja..

3 cC-W

A> 3-SS' l*M - KV'Aft

a-KXlo' ^S**'*^Sy

\ - - **2 *- *S A- . C JL 15 uf in -==

3. A ,i-phase. 220 V. 50 Hz. 11.2 kW induction motor has a full loud efficiency of 88% and draws a line current of 38 A under full load, when comicctcd to a .1-phase. 220 V supply.

a) Determine the p.f. at which the motor is operating. [2]

1'7* h'

1 o-tt f~ ^a'^{< 3t}*

b) Find the raiding on the two wnttn>etcrs conncctcd in the circuit 10 treasure the input to the motor. |2|

V*V ^v(-"O - t***-

W* * tV + ?) tv

4. A ring of maifnctic material has a ivc(angular cross scction. The inner diameter of the rirtg is 20 cm nnd the outer diameter is 25 cm, its thickness being 2 cm. An air gap of I mm length is cut across the ring. The ring is wound with 500 turns and when carrying a cum.nl of 3 A produces a flux density of 1.2 Tin the air gnp. Find a) Draw the equivalent electrical circuit for the above magnetic circuit. 111

Timr : 5fl Min Tulal Marks: 4(1

Quiz>ll of Ell 101 Kkctrical Sciencc 15 March 2011

1. Fill in (he blanks. |5|

i> I hive 10 fl resistors arc connected in delta on a 208 V. 3-phase line. If the fuse in tme line hums out. the power supplied to the UkhI will be mJ .

In a given magnetic circuit, a current of I A flowing in the exciting winding pnHitn.es a flux of 1 Wb. If the circuit reluctance is doubled, then for producing the same flux, the excitingcurrcnl should be 2 A _+*. J_riu, ['. jUmx; "-ni i iii

ii)

In I lie devirumatineik relay shown, the reluciancc of (he iron path is negligible. ITie expression for the self inductance of ihc coil would be ^x/*-*

'ii)

iv)

I- C

A 6600 V. 50 llz transformer operate at a flux density nf 1.5 T. Each linear dimension of the core is doubled while the primary and secondary turns arc halved. If the transformer is now operated at 13200 V. 50 Hz. the core tlux densitv will be

i.gr

_t

v) A 220115 V. 25 M/. 1 -pli.isc iransfonner has eddv current loss uf 100 W which is

half of the curc loss ai rated applied voltage. It' (his transformer is used with primary connected to a 440 V. 50 tfc mains, the total core loss would be Igc i/J .

f.

u mam - -i

xt<v t tin** -

2. Three coils cach having a resistance of 20 U and a reactance of 15 U are connected in star to a 400 V'. 3-phase. 50 H/ supply. Calculate

a) Line current i²l

^vt ¹ Yit. m . Ato-m *

Vfh ₅ S'+f-P¹

z il'

Active power supplied

p - V_wi_tkj* - A *4*> yi-t'i 1S<1 fc-vJ

\

- !-

b)

in

c) Power factor

IH

0.

iii') -

6. Draw the phasor diagram (neat nnd clean) of a real transformer at leading p.f. load. |3|

7. A single phase 44 kVA. 50 H?, 2200/220 V transformer has the following parameters: high voltage side impcdancc, *(0.4 + low voltage side impcdancc.

2_ft. io.oi* jOMiO. magnetizing reactance and core loss resistance {referred to Iv side) arc 205 ft and HO Q. respectively.

a) Draw the exact equivalent circuit diagram (with values ol' impcdances shown in the circuit iisdl) referred to the hv side. |2|