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A current transformer must at all times have (a) a secondary load (b) short circuited secondary (c) either (a) or (b) (d) none of these

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For a constant load current, transformer maximum efficiency occurs at   (a) any power factor (b) zero power factor leading (c) zero power factor lagging (d) unity power factor 

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For a transformer, operating at constant load current, maximum efficiency will occur at?

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The kVA rating required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV will be: A. 4 kVA B. 0.25 kVA C. 16 kVA D. 8 kVA

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The driving point impedance with poles at ω = 0(zero) and ω = ∞ (infinity) must have the  (a) s term in the denominator and an excess term in the numerator (b) s term in the numerator and an excess term in the denominator (c) s term in the numerator and equal number of terms in the numerator and denominator (d) s term in the denominator and equal number of terms in the numerator and denominator

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The path of magnetic flux in a transformer should have?

asked Mar 19, 2018 in Transformer by Shimroz123
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When the SCR conducts, the forward voltage drop will   (a) 0.7 V at all load current (b) 2 to 2.5 V at all load current (c) increases slightly with load current (d) remains constant with load current 

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
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Full load copper loss in a transformer is 1600 watts. At half load the copper loss will be: A) 6400 watt B) 1600 watt C) 800 watt D) 400 watt

asked Jun 4, 2018 in Transformer by Shimroz123
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The voltage regulation of a transformer, with ohmic drop 2% and reactance drop 5% of the voltage at 0.8 lagging power factor, will be (a) 7% (b) 5.6% (c) 5.3% (d) 4.6%

asked May 25, 2018 in Transformer by Shimroz123
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In a transformer the voltage regulation will be zero when it operates at (A) unity p.f. (B) leading p.f. (C) lagging p.f. D) zero p.f. leading.

asked May 22, 2018 in Transformer by Shimroz123
1 answer 17 views

A simple phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is  (A) 86.7% (B) 88.26% (C) 88.9% (D) 87.8%

asked May 17, 2018 in Transformer by Shimroz123
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A single-phase, 50 kVA, 250 V/500 V two winding transformer has an efficiency of 95% at full load, unity power factor. If it is re-configured as a 500 V/750 V auto-transformer, its efficiency at its new rated load at unity power factor will be  (A) 95.752% (B) 97.851% (C) 98.276% (D) 99.241%

asked May 17, 2018 in Transformer by Shimroz123
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If the secondary turns of a transformer are doubled and at the same time primary voltage is reduced to half then the secondary voltage will

asked May 15, 2018 in Transformer by Shimroz123
1 answer 16 views

In a transformer, zero voltage regulation at full load is   (a)Not possible   (b) Possible at unity power factor load   (c) Possible at leading power factor load   (d) Possible at lagging power factor load

asked May 13, 2018 in Transformer by Shimroz123
1 answer 23 views

The current transformer that is used to measure a 100 A current by 5 A ammeter is a_____.

asked May 29, 2018 in Transformer by Shimroz123
1 answer 41 views

The hysteresis and eddy current losses of a single phase transformer working on 200 V, 50 Hz supply are Ph and Pe respectively. The percentage decrease in these when operated on a 160 V, 40 Hz supply are   (a) 32, 36 (b) 20, 36 (c) 25, 50 (d) 40, 80 

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When secondary of a current transformer is open-circuited its iron core will be?

asked Mar 19, 2018 in Transformer by Shimroz123
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The secondary of a current transformer is always short-circuited under operating conditions because it?

asked Mar 19, 2018 in Transformer by Shimroz123
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In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of?

asked Mar 19, 2018 in Transformer by Shimroz123
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A highly conductive material must have?

asked Mar 28, 2018 in Electrical engineering materials by Shimroz123
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A series RLC circuit resonate at 200 Hz. If the capacitance is increased to four times, the circuit will be in resonance at   (a) 100 Hz (b) 200 Hz (c) 400 Hz (d) 800 Hz  

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1 answer 21 views

Two copper conductors have equal length. The cross-sectional area of one conductor is four times that of the other. If the conductor having smaller cross-sectional area has a resistance of 40 ohms the resistance of other conductor will be?

asked Mar 25, 2018 in Basic concepts by Shimroz123
2 answers 38 views

The inrush current of a transformer at no load is maximum if the supply voltage is switched on  (1) at peak voltage value (2) at zero voltage value (3) at half voltage value (4) at 0.866 time voltage value

asked Apr 30, 2018 in Switchgear And Protection by Shimroz123
1 answer 24 views

A transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and frequency are doubled, the new core losses are (A) 140 W (B) 180 W (C) 240 W (D) 480 W

asked Apr 28, 2018 in Electrical Engineering by Shimroz123
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A large transformer operating at no load draws an exciting current Io of 5A, when the primary is connected to a 120 V, 60 Hz source. From a wattmeter test, it is known that iron losses are equal to 180 W. Calculate the reactive power absorbed by the core.  (A) 600 var (B) 572 var (C) 180 var (D) 360 var 

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 The no-load current drawn by transformer is usually what per cent of the full-load current ?

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In a hydel power station, the number of poles of an alternator is 24. At what rpm the alternator must be driven to produce 50 Hz voltage?

asked Apr 3, 2018 in Lesson 2 Generation, Transmission and Distribution of Electric Power an Overview by Shimroz123
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An accurate voltmeter must have an internal impedance of (A) very low value. (B) very high value (C) medium value. (D) zero Value

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In a series parallel circuit, any two resistances in the same current path must be in?

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The all-day efficiency of a transformer is the ratio of (1) kWh output and kWh input per day (2) kWh output and kWh input in a day (3) output power and input power (4) input power and output power

asked Apr 11, 2018 in Electrical Engineering by Shimroz123
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Which type of generator gives a constant voltage output at all loads?

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If all transmission zeros of a network are at origin, it is a  A) HPF B) LPF C) BPF D) BEF 

asked Apr 9, 2018 in Electronics Engineering by Shimroz123

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