A three-phase star -connected load is operating at a power factor angle ϕ with ϕ being the angle between

A three-phase star -connected load is operating at a power factor angle ϕ  with ϕ being the angle between
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A three-phase star -connected load is operating at a power factor angle ϕ  with ϕ being the angle between Phase voltage and phase current

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In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltage in the two cases. (A) delta side lags by -30°. (B) star side lags by -30°. (C) delta side leads by 30°. (D) star side leads by -30°.

Description : In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltage in the two cases. (A) delta side lags by -30°. (B) star side lags by -30°. (C) delta side leads by 30°. (D) star side leads by -30°.

Last Answer : Ans: C This is vector group and has +30° displacement. Therefore, delta side leads by +30°.

A 3-phase voltage source inverter operates in 180° conduction mode with a star connected resistive load. If input

Description : A 3-phase voltage source inverter operates in 180° conduction mode with a star connected resistive load. If input dc voltage is 100 V, then the peak to peak output line voltage is :

Last Answer : A 3-phase voltage source inverter operates in 180° conduction mode with a star connected resistive load. If input dc voltage is 100 V, then the peak to peak output line voltage is : 200 V

A alternator is delivering power to a balanced load at unit power factor. The phase angle between the line...

Description : A alternator is delivering power to a balanced load at unit power factor. The phase angle between the line voltage and the line current is? (A) 90° (B) 60° (C) 30° (D) 0° 

Last Answer : A alternator is delivering power to a balanced load at unit power factor. The phase angle between the line voltage and the line current is 30°

A three-phase alternator is operating at 450 volts, 250 amps at 0.6 power factor. If the power factor increases to 0.8, the kw load potential will increase by _____________. A. 38.525 kw B. 116.91 kw C. 155.88 kw D. 194.85 kw

Description : A three-phase alternator is operating at 450 volts, 250 amps at 0.6 power factor. If the power factor increases to 0.8, the kw load potential will increase by _____________. A. 38.525 kw B. 116.91 kw C. 155.88 kw D. 194.85 kw

Last Answer : Answer: A

A three-phase synchronous motor connected to ac mains is running at full load and unity power factor.

Description : A three-phase synchronous motor connected to ac mains is running at full load and unity power factor. lf its shaft load is reduced by half and field current is held constant then its new power factor will be

Last Answer : Leading

A 3~phase synchronous motor, connected to infinite bus, is operating at no load at normal excitation. ...

Description : A 3~phase synchronous motor, connected to infinite bus, is operating at no load at normal excitation. The field excitation of the motor is first decreased to zero and then increased in the ... 2) First decrease and then increase, (3) Increases continuously (4) First increase and then decreased

Last Answer : A 3~phase synchronous motor, connected to infinite bus, is operating at no load at normal excitation. The field excitation of the motor is first decreased to zero and then increased in the reverse direction. The armature current of the synchronous motor will: Increases continuously.

The power factor of an AC generator operating singularly is determined by the __________. A. connected load B. prime mover speed C. field excitation D. generator's rated voltage

Description : The power factor of an AC generator operating singularly is determined by the __________. A. connected load B. prime mover speed C. field excitation D. generator's rated voltage

Last Answer : Answer: A

To equalize the power factor of two alternators operating in parallel, the ____________. A. field excitation of both units is adjusted B. governors of both units are adjusted C. phase sequence is altered D. kilowatt load is evenly divided

Description : To equalize the power factor of two alternators operating in parallel, the ____________. A. field excitation of both units is adjusted B. governors of both units are adjusted C. phase sequence is altered D. kilowatt load is evenly divided

Last Answer : Answer: A

Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in armature reaction are compensated for by the __________ A. governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Description : Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in ... . governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Last Answer : Answer: B

An artificial neurons receives n inputs x1, x2,...,xn with weights w1,w2,...,wn attached to the input links. The weighted sum ............... is computed to be passed on to a non-linear filter ϕ called activation function to release the output. (A) Σ wi (B) Σ xi (C) Σ wi + Σ xi (D) Σ wi . Σ xi

Description : An artificial neurons receives n inputs x1, x2,...,xn with weights w1,w2,...,wn attached to the input links. The weighted sum ............... is computed to be passed on to a non-linear filter ϕ called activation function to release the output. (A) Σ wi (B) Σ xi (C) Σ wi + Σ xi (D) Σ wi . Σ xi

Last Answer : (D) Σ wi . Σ xi

Consider the languages L1 = ϕ, and L2 = {1}. Which one of the following represents L1* U L2* L1* ? (1) {ε} (2) {ε,1} (3) ϕ (4) 1*

Description : Consider the languages L1 = ϕ, and L2 = {1}. Which one of the following represents L1* U L2* L1* ? (1) {ε} (2) {ε,1} (3) ϕ (4) 1*

Last Answer : 1*

In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load,

Description : In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load, the input source current is (A) sinusoidal current (B) constant dc current (C) continuous rectangular pulses (D) alternating rectangular pulses

Last Answer : In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load, the input source current is alternating rectangular pulses

A three phase transmission line delivers a load of 5 MW at 0.8 power factor lagging. Resistance of each...

Description : A three phase transmission line delivers a load of 5 MW at 0.8 power factor lagging. Resistance of each conductor is 0.5 ohm / km. Receiving end voltage is 33 kV. If the line loss is not to exceed 10%, determine the length of the line.  (A) 7 km (B) 27.9 km (C) 56.8 km (D) 13.9 km

Last Answer : B

What is the power factor when a single phase watt meter operating on 200 V and 5 A for 5 hours makes 2016

Description : What is the power factor when a single phase watt meter operating on 200 V and 5 A for 5 hours makes 2016 revolutions and the meter constant in revolution is 420? A) 0.04 B) 1.04 C) 0.96 D) None of these

Last Answer : What is the power factor when a single phase watt meter operating on 200 V and 5 A for 5 hours makes 2016 revolutions and the meter constant in revolution is 420? A) 0.04 B) 1.04 C) 0.96 D) None of these

A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred

Description : A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is (A) 216 V (B) 226 V (C) 234 V (D) 236 V

Last Answer : A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is 226 V

A 3-phase star-connected 75 MVA, 25 kV 3-phase synchronous generator has a synchronous reactance of...

Description : A 3-phase star-connected 75 MVA, 25 kV 3-phase synchronous generator has a synchronous reactance of 1.0 p.u. The per unit value to a 90 MVA base and 30 kV is (A) 2/15 p.u. (B) 5/6 p.u. (C) 1.0 p.u. (D) 1.2 p.u.

Last Answer : A 3-phase star-connected 75 MVA, 25 kV 3-phase synchronous generator has a synchronous reactance of 1.0 p.u. The per unit value to a 90 MVA base and 30 kV is 5/6 p.u.

A large transformer operating at no load draws an exciting current Io of 5A, when the primary is connected to...

Description : 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 ... power absorbed by the core.  (A) 600 var (B) 572 var (C) 180 var (D) 360 var 

Last Answer : 572var

A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kw meter currently indicates 163.6 KW, with a power factor of 0.7. If the power factor increases to 0.8, the KW meter would then read ____________. A. 181.4 KW B. 186.8 KW C. 194.2 KW D. 201.4 KW

Description : A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kw meter currently indicates 163.6 KW, with a power factor of 0.7. If the power factor increases to 0.8, the KW meter would then read ____________. A. 181.4 KW B. 186.8 KW C. 194.2 KW D. 201.4 KW

Last Answer : Answer: B

A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kw meter currently indicates 163.6 KW, with a power factor of 0.7. If the power factor increases to 0.8, the KW meter reading would increase by ___ A. 17.8 KW B. 23.2 KW C. 30.6 KW D. 37.8 KW

Description : A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kw meter currently indicates 163.6 KW, with a power factor of 0.7. If the power factor increases to 0.8, the KW meter reading would increase by ___ A. 17.8 KW B. 23.2 KW C. 30.6 KW D. 37.8 KW

Last Answer : Answer: B

A three phase induction motor is drawing 16 Ampere at 440 Volts. If the operating power factor of the motor is 0.90 and the motor efficiency is 92%, then the mechanical shaft power output of the motor is a) 12.04 kW b) 10.09 kW c) 10.97 kW d) None of the above

Description : A three phase induction motor is drawing 16 Ampere at 440 Volts. If the operating power factor of the motor is 0.90 and the motor efficiency is 92%, then the mechanical shaft power output of the motor is a) 12.04 kW b) 10.09 kW c) 10.97 kW d) None of the above

Last Answer : b) 10.09 kW

A three-phase transformer, connected in star-delta, is composed of three single-phase transformers, each

Description : A three-phase transformer, connected in star-delta, is composed of three single-phase transformers, each rated 127/ 13.2 kV. The line-to-line voltage ratio for the three-phase transformer is: A) 220 / 13.2 kV B) 127 / 13.2 kV C) 127 / 220 kV D) 220 / 220 kV

Last Answer : A three-phase transformer, connected in star-delta, is composed of three single-phase transformers, each rated 127/ 13.2 kV. The line-to-line voltage ratio for the three-phase transformer is: 220 / 13.2 kV 

In a three phase transformer, if the primary side is connected in star and secondary side is connected in...

Description : In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, the angle difference between phase voltage in the two cases will be: (A) delta side will lag by -30° ... will lag by -30° (C) delta side will lead by 30° (D) star side will lead by -30°

Last Answer : In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, the angle difference between phase voltage in the two cases will be: delta side will lead by 30° 

In a Y -connected circuit, between each line -voltage and the nearest phase - voltage, there is a phase -angle of:

Description : In a Y -connected circuit, between each line -voltage and the nearest phase - voltage, there is a phase -angle of: A. 0° B. 30° C. 60° D. 120°

Last Answer : B

A single phase 60 Hz generator supplies an inductive load of 4500kW at a power factor of 0.80 lagging ...

Description : A single phase 60 Hz generator supplies an inductive load of 4500kW at a power factor of 0.80 lagging by means of a 20 km long overhead transmission line. The line resistance and inductance are 0.0195 ohm and 0.60 mH ... voltage regulation of the line.  (A) 12.59% (B) 16.34% (C) 32.68% (D) 41.15% 

Last Answer : Answer is C

4. A three-phase, four-wire system having \( 250 V \) line-to-neutral has the following loads connected between the respective lines and the neutral. Calculate the current in the neutral wire?\[Z_{R}=20 \angle 0^{\circ} \Omega ; Z_{Y}=20 \angle 35^{\circ} \Omega, Z_{B}=20 \angle-55^{\circ} \Omega\](10M)

Description : 4. A three-phase, four-wire system having \( 250 V \) line-to-neutral has the following loads connected between the respective lines and the neutral. Calculate the current in the neutral wire?\[Z_{R}=20 \angle 0^{\circ} ... Z_{Y}=20 \angle 35^{\circ} \Omega, Z_{B}=20 \angle-55^{\circ} \Omega\](10M)

Last Answer : 4. A three-phase, four-wire system having \( 250 V \) line-to-neutral has the following loads connected ... =20 \angle-55^{\circ} \Omega \] (10M)

4. A three-phase, four-wire system having \( 250 V \) line-to-neutral has the following loads connected between the respective lines and the neutral. Calculate the current in the neutral wire?\[Z_{R}=20 \angle 0^{\circ} \Omega ; Z_{Y}=20 \angle 35^{\circ} \Omega, Z_{B}=20 \angle-55^{\circ} \Omega\](10M)

Description : 4. A three-phase, four-wire system having \( 250 V \) line-to-neutral has the following loads connected between the respective lines and the neutral. Calculate the current in the neutral wire?\[Z_{R}=20 \angle 0^{\circ} ... Z_{Y}=20 \angle 35^{\circ} \Omega, Z_{B}=20 \angle-55^{\circ} \Omega\](10M)

Last Answer : 4. A three-phase, four-wire system having \( 250 V \) line-to-neutral has the following loads connected ... =20 \angle-55^{\circ} \Omega \] (10M)

4. A three-phase, four-wire system having \( 250 V \) line-to-neutral has the following loads connected between the respective lines and the neutral. Calculate the current in the neutral wire?\[Z_{R}=20 \angle 0^{\circ} \Omega ; Z_{Y}=20 \angle 35^{\circ} \Omega, Z_{B}=20 \angle-55^{\circ} \Omega\](10M)

Description : 4. A three-phase, four-wire system having \( 250 V \) line-to-neutral has the following loads connected between the respective lines and the neutral. Calculate the current in the neutral wire?\[Z_{R}=20 \angle 0^{\circ} ... Z_{Y}=20 \angle 35^{\circ} \Omega, Z_{B}=20 \angle-55^{\circ} \Omega\](10M)

Last Answer : 4. A three-phase, four-wire system having \( 250 V \) line-to-neutral has the following loads connected ... =20 \angle-55^{\circ} \Omega \] (10M)

Which of the following statements is true concerning all three-phase alternators? A. Each has three separate but identical armature windings acted on by one system of rotating magnets. B. Each has one armature winding acted on by three identical but separate systems of rotating magnets. C. All three-phase alternators are designed to operate with a 0.8 leading power factor. D. The three phases always provide power to the load through three sets of slip rings and brushes.

Description : Which of the following statements is true concerning all three-phase alternators? A. Each has three separate but identical armature windings acted on by one system of rotating magnets. B. Each has one ... The three phases always provide power to the load through three sets of slip rings and brushes.

Last Answer : Answer: A

A transmission line is operating with a Phase shift of 80° between two ends. If the load is suddenly increased

Description : A transmission line is operating with a Phase shift of 80° between two ends. If the load is suddenly increased A) The phase displacement will increase B) The phase displacement will decrease C) The phase displacement will not change D) The surge impedance will increase

Last Answer : A transmission line is operating with a Phase shift of 80° between two ends. If the load is suddenly increased The phase displacement will increase

A two-phase generator is connected to two 9012 load resistors. Each coil generates 120 V ac. The value of ...

Description : A two-phase generator is connected to two 90Ω load resistors. Each coil generates 120 V ac. The value of current flowing through the common neutral line will be: A. 1.33 A B. 1.88 A C. 2.66 A D. 1.77 A

Last Answer : A two-phase generator is connected to two 90Ω load resistors. Each coil generates 120 V ac. The value of current flowing through the common neutral line will be: 1.77 A

A single phase energy meter has a constant of 1200 revolution/kWh. When a load of 200 W is connected,...

Description : A single phase energy meter has a constant of 1200 revolution/kWh. When a load of 200 W is connected, the disc rotates at 4.2 revolutions per min. If the load is on for 10 hours, the meter records an excess of   (a) 0.1 kWh (b) 0.2 kWh (c) 1.0 kWh (d) 2.0 kWh 

Last Answer : 2

To check the three line fuses of a three-phase system consisting of a three-phase motor, you must _____________. A. place the starter in the 'stop' position B. make sure the motor is operating at full load to guard against a false reading C. place the leads across the 'hot' ends of the fuses D. place the leads across the bottom ends of the fuses

Description : To check the three line fuses of a three-phase system consisting of a three-phase motor, you must _____________. A. place the starter in the 'stop' position B. make sure the motor is operating at full ... leads across the 'hot' ends of the fuses D. place the leads across the bottom ends of the fuses

Last Answer : Answer: A

at the terminal of a three-phase 6.6Kv alternator a load R=200 ohm is connected between two-phase and the third phase is opened. Z1=z2=5 ohm Zo=2 find out the fault current .

Description : at the terminal of a three-phase 6.6Kv alternator a load R=200 ohm is connected between two-phase and the third phase is opened. Z1=z2=5 ohm Zo=2 find out the fault current .

Last Answer : 32A

A three phase, salient pole synchronous motor is connected to an infinite bus. It is operated at no load a

Description : A three phase, salient pole synchronous motor is connected to an infinite bus. It is operated at no load a normal excitation. The field excitation of the motor is first reduced to zero ... First increases and then decreases steeply (C) First decreases and then increases steeply (D) Remains constant

Last Answer : B

Two wattmeters connected to measure the power input to a balanced three-phase circuit indicate ...

Description : Two wattmeters connected to measure the power input to a balanced three-phase circuit indicate 4.5 KW and 3 KW respectively. Find the power factor of the circuit. A. 0.7 B. 0.8 C. 0.95 D. 0 

Last Answer : Two wattmeters connected to measure the power input to a balanced three-phase circuit indicate 4.5 KW and 3 KW respectively. Find the power factor of the circuit.  0.95

Which of the following statements is correct concerning the motor performance curves and data table shown in the illustration? EL-0006 A. The motor RPM at full load is 1737 RPM. B. The motor draws 12.62 kw from the switchboard when operating at full load. C. If the motor was developing 10 HP its power factor would be 0.92. D. All of the above.

Description : Which of the following statements is correct concerning the motor performance curves and data table shown in the illustration? EL-0006 A. The motor RPM at full load is 1737 RPM. B. The motor draws 12.62 kw ... If the motor was developing 10 HP its power factor would be 0.92. D. All of the above.

Last Answer : Answer: D

If the excitation of an alternator operating in parallel is decreased below normal, its _____________. A. power factor will change in the lagging direction B. power factor will change in the leading direction C. ampere load will be greatly increased D. kilowatt load will be greatly decreased

Description : If the excitation of an alternator operating in parallel is decreased below normal, its _____________. A. power factor will change in the lagging direction B. power factor will change in the leading direction C. ampere load will be greatly increased D. kilowatt load will be greatly decreased

Last Answer : Answer: B

To remove an alternator operating in parallel with another unit from the main electrical bus, you must FIRST _________. A. adjust the power factor on both units B. set the desired voltage on the outgoing alternator C. open the circuit breaker on the outgoing alternator D. remove the load from the outgoing alternator

Description : To remove an alternator operating in parallel with another unit from the main electrical bus, you must FIRST _________. A. adjust the power factor on both units B. set the desired voltage on ... C. open the circuit breaker on the outgoing alternator D. remove the load from the outgoing alternator

Last Answer : Answer: D

If the excitation is increased to one of two alternators operating in parallel, the _____________. A. power factor will change in the lagging direction B. power factor will change in the leading direction C. kilowatt load will be greatly increased D. ampere load will be greatly decreased

Description : If the excitation is increased to one of two alternators operating in parallel, the _____________. A. power factor will change in the lagging direction B. power factor will change in the leading direction C. kilowatt load will be greatly increased D. ampere load will be greatly decreased

Last Answer : Answer: A

Using illustrated chart, when will the power factor be least efficient? EL-0006 A. When the motor is operating at full load. B. When the percentage of slip is greatest. C. When there is no load on the motor. D. the power factor is the same from no-load to locked rotor.

Description : Using illustrated chart, when will the power factor be least efficient? EL-0006 A. When the motor is operating at full load. B. When the percentage of slip is greatest. C. When there is no load on the motor. D. the power factor is the same from no-load to locked rotor.

Last Answer : Answer: C

A synchronous motor is operating on no-load at unity power factor. If the field current is increased, power factor will become (A) Leading & current will decrease (B) Lagging & current will increase. (C) Lagging & current will decrease. (D) Leading & current will increase.

Description : A synchronous motor is operating on no-load at unity power factor. If the field current is increased, power factor will become (A) Leading & current will decrease (B) Lagging & current will increase. (C) Lagging & current will decrease. (D) Leading & current will increase.

Last Answer : Ans: A Initially synchronous motor is operating at no load and unity power factor. When field current increases, the excitation will increase. Therefore, p.f will be leading and current will be I CosΦ < I

Which of the following meters uses a shunt connected in series with the load, but parallel with the meter movement? A. voltmeter B. power factor meter C. wattmeter D. ammeter

Description : Which of the following meters uses a shunt connected in series with the load, but parallel with the meter movement? A. voltmeter B. power factor meter C. wattmeter D. ammeter

Last Answer : Answer: D

Which of the listed meters uses a shunt connected in series with the load, but parallel with the meter movement? A. Voltmeter B. Power factor meter C. Ammeter D. Wattmeter

Description : Which of the listed meters uses a shunt connected in series with the load, but parallel with the meter movement? A. Voltmeter B. Power factor meter C. Ammeter D. Wattmeter

Last Answer : Answer: C

The power factor at which a paralleled AC generator operates is usually adjusted by the _____________. A. connected load B. prime mover speed C. field excitation D. generator's rated voltage

Description : The power factor at which a paralleled AC generator operates is usually adjusted by the _____________. A. connected load B. prime mover speed C. field excitation D. generator's rated voltage

Last Answer : Answer: C

In power system, if a voltage controlled bus is treated as a load bus then which one of the following limits would be violated? a) Voltage b) Active power c) reactive power d) Phase angle

Description : In power system, if a voltage controlled bus is treated as a load bus then which one of the following limits would be violated? a) Voltage b) Active power c) reactive power d) Phase angle

Last Answer : a) Voltage

In load flow studies of a power system, a voltage control bus is specified by a) Real power and reactive power b) Reactive power and voltage magnitude c) Voltage and voltage phase angle d) Real power and voltage magnitude

Description : In load flow studies of a power system, a voltage control bus is specified by a) Real power and reactive power b) Reactive power and voltage magnitude c) Voltage and voltage phase angle d) Real power and voltage magnitude

Last Answer : d) Real power and voltage magnitude

The locked rotor current in a 3-phase, star connected 15 , kW 4 , pole 230 V , 50 Hz induction motor at rated

Description : The locked rotor current in a 3-phase, star connected 15 , kW 4 , pole 230 V , 50 Hz induction motor at rated conditions is 50 A. Neglecting losses and magnetizing current, the approximate locked rotor line current drawn when the motor ... Hz supply is  (A) 58.5 A (B) 45.0 A (C) 42.7 A (D) 55.6 A

Last Answer : The locked rotor current in a 3-phase, star connected 15 , kW 4 , pole 230 V , 50 Hz induction motor at rated conditions is 50 A. Neglecting losses and magnetizing current, the approximate locked rotor line current drawn when the motor is connected to a 236 , V 57 Hz supply is 45.0 A 

A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u.

Description : A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u. The actual value of x1 referred to the low voltage side is (A) 0.85 Ω (B) 3.63 Ω (C) 36.3 Ω (D) 252 Ω

Last Answer : A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u. The actual value of x1 referred to the low voltage side is 3.63 Ω