thrite arrestor question bank

8/12/2019 thrite arrestor question bank

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thrite arrestor

rod gap

horn gap

expulsion type

1.first nuclear plant commissioned in england

2. Indias 1st nuclear plant at Kalpakam

3.Safety factor of insulator=flash over voltage /puncture strength

4.Keeping in view the cost and overall effectiveness, the following circuit breaker is suitedfor capacitor bank switching--oil

1.When D is the diameter of fuse wire, the fusing current will be proportional toD^3/2

2. A material best suited for manufacturing of fuse wire isSilver

3. In a circuit breaker the current which exists at the instant of contact separation is known

as-Breaking current

4. A Merz-price protection is suitable for-Alternators

5. 'Kick fuse' has-inverse characteristic

6. Air blast circuit breakers for 400 kV. Power system are designed to operate in-50 milli sec

7. Breaking capacity of a circuit breaker is usually expressed in terms of-MVA

8. The arc voltage produced in ac circuit breaker isin phase with current

9. When n resistances each of value r are connected in parallel, then resultant resistance is

x. When these n resistances are connected in series, total resistance is

(A) nx

(B) rnx

(C) x / n

(D) n2x.


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10.Resistance of a wire is r ohms. The wire is stretched to double its length, then its

resistance in ohms is

(A) r / 2

(B) 4 r

(C) 2 r

(D) r / 4.

11. The mass of proton is roughly how many times the mass of an electron?1840

12. The charge on an electron is known to be 1.6 x 10-19coulomb. In a circuit the current

flowing is 1 A. How many electrons will be flowing through the circuit in a second?

(A) 1.6 x 1019

(B) 1.6 x 10-19

(C) 0.625 x 1019

(D) 0.625 x 1012.

13. A copper wire of length l and diameter d has potential difference V applied at its two

ends. The drift velocity is vd. If the diameter of wire is made d/3, then drift velocity becomes

(A) 9 vd

(B) vd/ 9

(C)vd/3

(D)vd.


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14.

R=5/6R

15.Which method can be used for absolute measurement of resistances ?

(A)Ohm's law method

(B)Wheatstone bridge method

(C)Releigh method

(D) Lortentz method.

16. Three 3 ohm resistors are connected to form a triangle. What is the resistance between

any two of the corners?

(A) 3 / 4 ohms

(B) 3 ohms

(C) 2 ohms

(D) 4/3 ohm.

17. Low resistance can be accurately measured by

(A) Kelvin bridge

(B )Wheat stone bridge

(C) Wein's bridge

(D) None of the above.

18.


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Frequency of Synchronous Generator:

The frequency of the voltage generated is given by

f = NP/120

where P is the total number of poles and N is the speed in r.p.m.

Breadth factor of Synchronous Generator:

(Kb) = Voltage obtained in multi-slots winding / Voltage obtained if the windings wereall concentrated in one slot

Thus breadth factor is always less than unity.

Mathematically,

Kb= (sin n/2 )/ ( sin /2)

where n is the number of slot and is the slot pitch.

Pitch factor of Synchronous Generator:

Shortening the pitch of the coil has the same effect as the distribution of the winding. Whenthe turns of the windings do to span a complete pitch there occurs a slight loss in theinduced emf. A pitch factor ( Kp)is given by

Kp= cos /2

for a coil which extends over (180 - ) instead of 180.

Magnitude of Induced emf in alternators / phase:

ERMS = 4.44 Kp Kb f.T. volts

Synchronous Reactance:

Xs= XL+ XA

XL= Leakage reactance;

XA= Armature reactance.

Synchronous Impedance:

Zs= (R2+ X2s)

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1.The number of electrical degrees passed through in one revolution of a six pole

synchronous alternator is

(A)360:

(B)720

(C) 1080

(D)2160 .

2.

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thrite arrestor question bank