The low voltage winding of a 400/230 V, 1-phase, 50 Hz transformer is to be connected to a 25 Hz, the supply voltage should be

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Answer :

The low voltage winding of a 400/230 V, 1-phase, 50 Hz transformer is to be connected to a 25 Hz, the supply voltage should be 115 V.

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Last Answer : 3500

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Description : A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both ... same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.

Last Answer : (A) Both eddy current and hysteresis losses decreases.

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Description : A 230 V, 50 Hz phase controlled single-phase full-controlled SCR bridge converter draws 15 A constant dc current. If the source inductance is 3 mH, the drop in dc output voltage is (A) 4.5 V (B) 6.75 V (C) 9 V (D) 13.5 V

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Last Answer : (c) 230 V

Description : The voltage of the single phase supply to residential consumers is (a) 110 V (b) 210 V (c) 230 V (d) 400 V

Last Answer : (c) 230 V

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Description : A 400 V, 50 Hz 30 hp, three-phase induction motor is drawing 50 A current at 0.8 power factor lagging. The stator and rotor copper losses are 1.5 kW and 900 W respectively. The friction and windage losses are 1050 W and the ... the motor will be (A) 23.06 kW (B) 24.11 kW (C) 25.01 kW (D) 26.21 kW

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Description : A three phase 50 Hz line consists of three conductors each of diameter 21 mm, The spacing between the conductors all follows:A - B = 3m, B - C = 5m, C - A = 3.6mIf the line operates at 132 k V, the reactive voltampere generatd by the line per km is?

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Description : A 3-phase, 11 kv, 50 Hz, 200 kW load has a power factor of 0.8 lag. A delta connected 3-phase capacitor is used to improve the power factor to unity. The capacitance perphase of the capacitor in micro-farads is?

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Description : An AC supply of 230 V is applied to half wave rectifier circuit. A transformer turns ratio is 20 : 1. Find i) Output DC voltage (ii) Peak Inverse Voltage (PIV)

Last Answer : Solution:

Description : A 400 V, 15 kW, 4-pole, 50 Hz, Y-connected induction motor has full load slip of 4%. The output torque of the machine at full load is  (A) 1.66 Nm (B) 95.50 Nm (C) 99.47 Nm (D) 624.73 Nm

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Description : A 3-phase, 400 votts, 50 Hz, 100 KW, 4 pole squirrel cage induction motor with a rated slip of 2% will have a rotor speed of (A) 1500 rpm (B) 1470 rpm (C) 1530 rpm (D) 1570 rpm

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Description : A 3 phase, 400 volts, 50 Hz, 100 kW, 4 pole squirrel cage induction motor with a rated slip of 2% will have a rotor speed of: (A) 1500 rpm (B) 1470 rpm (C) 1530 rpm (D) 1570 rpm

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Description : A single phase transformer has resistance and reactance of 0.2 pu and 0.6 pu respectively. Its pu voltage regulation at 0.8 pf lagging would he

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Description : A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be (A) 4.5%. (B) less than 4.5%. (C) more than 4.5%. (D) 4.5% or more than 4.5%.

Last Answer : (C) more than 4.5%.

Description : A two -winding single phase transformer has a voltage regulation of 4.5% at full - load and unity power -factor. At full -load and 0.80 lagging power-factor, the voltage regulation will be: (A) 4.5% (B) less than 4.5% (C) more than 4.5% (D) none of the above

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Description : 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

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Description : A 60 Hz, 320 km lossless line has Bending end voltage 1.0 p.u, The receiving end voltage on no load is?

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Description : A 50 Hz, 4-pole, 500 MVA, 22 kV turbo-generator is delivering rated megavolt amperes at 0.8 power factor. Suddenly a fault occurs reducing in electric power output by 40%. Neglect losses and assume constant power input to the ... the time of fault will be  (A) 1.528 (B) 1.018 (C) 0.848 (D) 0.509

Last Answer : A 50 Hz, 4-pole, 500 MVA, 22 kV turbo-generator is delivering rated megavolt amperes at 0.8 power factor. Suddenly a fault occurs reducing in electric power output by 40%. Neglect losses and assume ... the shaft. The accelerating torque in the generator in MNm at the time of fault will be 1.018 

Description : The corona loss in a 50 Hz system is 0.25 kW/ph/km. At a frequency of 60 Hz, the corona loss would be   (a) 0.30 kW/ph/km (b) 0.36 kW/ph/km (c) 028 kW/ph/km (d) 0.21 kW/ph/km

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Description : For a 500 Hz frequency excitation, a 50 km long power line will be modeled as

Last Answer : For a 500 Hz frequency excitation, a 50 km long power line will be modeled as long line

Description : A two conductor 1 - pi line operates at 50 Hz.The diameter of each conductor is 20 mm and the spacing between the conductors is 3m, The height of conductor above the ground is 6 m. The capacitance of the line to neutral will be?

Last Answer : A two conductor 1 - pi line operates at 50 Hz. The diameter of each conductor is 20 mm and the spacing between the conductors is 3m, The height of conductor above the ground is 6 m. The capacitance of the line to neutral will be 9.7 pF/m.

Description : A two conductor 1 - pi line operates at 50 Hz.The diameter of each conductor is 4 cm and are spaced 6 m apart. What is the capacitive susceptance to neutral per km?

Last Answer : A two conductor 1 - pi line operates at 50 Hz. The diameter of each conductor is 4 cm and are spaced 6 m apart. 3.06 x 10-9 s/km is the capacitive susceptance to neutral per km.

Description : A two conductor 1 - pi line operates at 50 Hz. The diameter of each conductor is 2 cm and are spaced 3m apart. What is the line to line capacitance ?

Last Answer : A two conductor 1 - pi line operates at 50 Hz. The diameter of each conductor is 2 cm and are spaced 3m apart.  4.87 x 10-9 F/km is the line to line capacitance.

Description : A two conductor 1 - pi line operates at 50 Hz. The diameter of each conductor is 20 mm and the spacing between conductors is 3m. What is the inductance of each conductor per km?

Last Answer : A two conductor 1 - pi line operates at 50 Hz. The diameter of each conductor is 20 mm and the spacing between conductors is 3m. 1.19 kH/km is the inductance of each conductor per km.

Description :  A 1000 V/400 V power transformer has a nominal short-circuit voltage Vsc = 40%. Which one of the following statements is correct ?  (a) A voltage of 400 V appears across the short-circuited ... V.  (d) The primary voltage drops to 400 V, when the secondary terminals are short-circuited.

Last Answer :  A 1000 V/400 V power transformer has a nominal short-circuit voltage Vsc = 40%. Which one of the following statements is correct ? (a) A voltage of 400 V appears across the short-circuited ... 400 V. (d) The primary voltage drops to 400 V, when the secondary terminals are short-circuited.

Description : When a transformer is used to step down voltage, the low voltage winding is _____________. A. part of the core B. the primary coil C. not insulated D. the secondary coil

Last Answer : Answer: D

Description : In a transformer, low voltage winding is placed near the core in case of concentric windings so as to  1. Reduce the leakage flux 2. Reduce the insulation requirement 3. Reduce the risk of voltage shock in case of insulation breakdown 4. Reduce the ... a) 1, 2, 3 (b) 2, 3, 4 (c) 1, 2, 3, 4 (d) 2, 3

Last Answer : In a transformer, low voltage winding is placed near the core in case of concentric windings so as to  1. Reduce the leakage flux 2. Reduce the insulation requirement 3. Reduce the risk of voltage shock in case of insulation breakdown 4. Reduce ... ) 1, 2, 3 (b) 2, 3, 4 (c) 1, 2, 3, 4 (d) 2, 3

Description : A certain transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio is? A.0.2 B.0.4 C.5 D.25

Last Answer : A certain transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio is? A.0.2 B.0.4 C.5 D.25

Description : A solar cell of 350 V is feeding power to an ac supply of 440 V, 50 Hz through a 3-phase fully controlled bridge converter. A large inductance is connected in the dc circuit to maintain the dc current at 20 A ... thyristor will be reverse biased for a period of  (A) 125o (B) 120o (C) 60o (D) 55o

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