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Aptitude Test (Mathematics and Soft Skill) DDCET
BASIC ELECTRONICS
Basics of Science and Engineering (DDCET)
CONTROL SYSTEM ENGINEERING
DIGITAL ELECTRONICS
ELECTRICAL CIRCUIT ANALYSIS
ELECTRICAL ENERGY CONSERVATION AND AUDITING
ELECTRICAL ENGINEERING MATERIALS
ELECTRICAL MACHINES
ELECTRICAL VEHICLES
ELECTRICAL WIRING
ELECTROMAGNETICS
MEASUREMENT & INSTRUMENTATION
MICROPROCESSOR AND MICROCONTROLLER INTERFACING
POWER ELECTRONICS & DRIVES
POWER SYSTEM
SIGNALS & SYSTEMS
UTILIZATION OF ELECTRICAL ENERGY
ELECTRICAL MACHINES
Q11.
A 1 KVA, single phase, 50 Hz, 100/250 V transformer gives the following results on short circuit test conducted at high voltage side:
Voltmeter reading: 12.5 V; Ammeter reading: 4 A; wattmeter readin: 80 W.
The equivalent resistance referred to high voltage side will be _______.
20 ohms
5 ohms
10 ohms
40 ohms
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Solution
Q12.
A 3000/300 V transformer takes 0.8 A at power factor of 0.4 on open circuit. Magnetizing current of the transformer will be
0.73 A
0.53 A
0.33 A
0.83 A
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Solution
Q13.
Primary and secondary voltage of autotransformer are 500 V and 400 V repectively. When secondary current is 100 A, calculate % saving of copper
70%
80%
75%
78%
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Solution
Q14.
Calculate core area of 500 kVA , 1-phase, 50 Hz, 6600/5000 V auto transformer, emf per turn = 8 V, maximum flux density 1.3 Wb/square meter
234 sq cm
337 sq cm
277 sq cm
289 sq cm
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Solution
Q15.
In a transformer zero voltage regulation at full load is
not possible
possible at unity p.f.
possible at leading p.f.
possible at lagging p.f.
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Solution
Q16.
A transformer has copper loss of 1.5 % and reactance of 3.5 % when tested on load. If its full load regulation is -0.9 % find its power factor.
0.85 lagging
0.8 leading
0.85 leading
0.8 lagging
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Solution
Q17.
Transformer will operate at maximum efficiency when
Copper loss = Iron loss
Hysteresis Loss = Eddy current Loss
Eddy current Loss = Copper Loss
Hysteresis Loss = Copper Loss
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Solution
Q18.
No load efficiency of transformer is________than full load efficiency
same
lesser
greater
depends on load
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Solution
Q19.
Open circuit and short circuit tests on a 3 kVA, 230 / 230 V, 50 Hz, single phase transformer gave the following results:
OC test: 230 V, 2 A, 100 W
SC test: 15 V, 13 A, 120 W
Determine the efficiency of the transformer at full load and 0.80 power factor lagging.
96.60%
91.60%
98.60%
94.60%
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Solution
Q20.
A 1000 KVA transformer has an efficiency of 95% at full load and also at 60% of full load, both at unity power factor. Determine the efficiency of the transformer at 80% of full load and unity power factor
92.15%
95.15%
97.15%
93.15%
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Solution
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