Electrical Transformer Multiple choice Question (Electrical Mcqs) and Answer Part 7
Electrical Engineering Objective Question and Answer
121- For the same rating which of the following sets will be costly?
(A) Three phase transformer
(B) Three transformer each of single phase type
(C) Both will have identical Cost
Answer: (B)
122-Which of the following is not a fitting on transformer?
122-Which of the following is not a fitting on transformer?
(A) Breather
(B) Conservator
(C) Buchholz Relay
(D) Commutator
Answer: (D)
Answer: (D)
123- When K is the transformation ratio of the main transformer in Scott connections, the transformation ratio in Teaser transformer will be ?
(A) √3 K
(B) K/√3
(C) K/3
(D) 3K
Answer: (B)
124-The reactance of a transformer depends on
Answer: (B)
124-The reactance of a transformer depends on
(A) Size of the core
(B) Size of the tank
(C) leakage flux
(D) all of the above
Answer: (C)
125-if the frequency of the supply voltage is doubled, which loss will increase?
Answer: (C)
125-if the frequency of the supply voltage is doubled, which loss will increase?
(A) eddy current loss
(B) hysteresis loss
(C) Copper loss
(D) none of above
Answer: (A)
Answer: (A)
126- No load current in a transformer as a percentage of full load current is approximately
(A) 25%
(B) 15% to 20%
(C) 5% to 10%
(D) 1 to 3%
Answer: (D)
127-In a transformer maximum voltage regulation occurs when the power factor of load is?
Answer: (D)
127-In a transformer maximum voltage regulation occurs when the power factor of load is?
(A) Unity
(B) 0.5
(C) lagging
(D) loading
Answer: (C)
Answer: (C)
128-The regulation of good transformer should be near ?
(A) 1%
(B) 10%
(C) 50%
(D) 100%
Answer: (A)
Answer: (A)
129- In a step transformer which ratio has value of one ?
(A) E2/E1
(B) I2/I1
(C) F2/F1
(D) none of above
Answer: (C)
Answer: (C)
130-In a transformer maximum voltage regulation occurs when the power factor of load is ?
(A) unity
(B) 0.707
(C) lagging
(D) leading
Answer: (D)
Answer: (D)
131- Scott connections are used for ?
(A) Single phase to three phase transformation
(B) three phase to single phase transformation
(C) three phase to three phase and three phase to two phase transformation
(D) any of the above
Answer: (C)
Answer: (C)
132-In Scott connections, the neutral point divides the teaser winding in the ratio
(A) 1:3
(B) 1:2
(C) 1:1
(D) 1:4
Answer: (B)
Answer: (B)
133- In a large capacity transformer 5% of the turns at the ends of high voltage winding are provided with extra insulation to
(A) Provide protection against lightning
(B) Provide protection against corona
(C) provide protection due to surges occurring during switching operation
(D) for all above protection
Answer: (C)
134- The Permitivity of bakelite is approximately
Answer: (C)
134- The Permitivity of bakelite is approximately
(A) 1.0
(B) 2.2
(C) 4.4
(D) 44
Answer: (C)
135-The permitivity of transformer oil is about?
Answer: (C)
135-The permitivity of transformer oil is about?
(A) 1.0
(B) 2.2
(C) 22
(D) 44
Answer: (B)
136- Two 1 phase transformer with equal turns have impedance of A= ( 0.5 + j3 ) ohms and
B= ( 0.6 + j10 ) ohms with respect to secondary , if they operate in parallel their share of load will be?
Answer: (B)
136- Two 1 phase transformer with equal turns have impedance of A= ( 0.5 + j3 ) ohms and
B= ( 0.6 + j10 ) ohms with respect to secondary , if they operate in parallel their share of load will be?
(A) A = 21.8 kW , B=78.2 kW
(B) A= 40 kW , B= 60 kW
(C) A=60 kW , B= 40 kW
(D) A= 78.2 kW , B= 21.8 kW
Answer: (D)
137-Buchholz relay is used in
Answer: (D)
137-Buchholz relay is used in
(A) Lime protection
(B) Greater protection
(C) Transformer protection
(D) Motor protection
Answer: (C)
138- A 20 kVA, 440/220 V , single phase 50 Hz transformer has iron loss of 324 W. The copper loss is found to be 100 W when delivering half full-load current. The percentage of full load when the efficiency will be maximum is
Answer: (C)
138- A 20 kVA, 440/220 V , single phase 50 Hz transformer has iron loss of 324 W. The copper loss is found to be 100 W when delivering half full-load current. The percentage of full load when the efficiency will be maximum is
(A) 90%
(B) 81%
(C) 72%
(D) 64%
Answer: (A)
Answer: (B)
140- Maximum regulation of transformer occurs at?
Answer: (A)
139- There are two-----800 kW transformers each having a maximum efficiency of 98%but in one the maximum efficiency occurs at full load while in the other it occurs at half load.Each transformer is on full load for 4 hours; one half load for 6 hours and on one tenth load for 14 hours per day. Which transformer will have better all day efficiency ?
(A) Transformer with maximum efficiency at full load
(B) Transformer with maximum efficiency at half load
(C) Both will have same efficiency
Answer: (B)
140- Maximum regulation of transformer occurs at?
(A) rated KVA of transformer
(B) unity power factor
(C) lagging power factor
(D) leading power factor
Answer: (C)
Answer: (C)
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