Easy Objective 3P AC Circuits Questions – Electrical Engineering

#1📜 EE Pre-Board March 2013📘 PowerhouseEasy

In two-wattmeter method, the readings of the wattmeter will be identical when

ALoad in one of the phases is zero

BPower Factor in unity

CPower factor is 0.5

DNeutral is earthed

#2📜 EE Pre-Board March 2013📘 PowerhouseEasy

What is the minimum number of wattmeter required to measure unbalanced power for a three phase system?

A2

B3

C4

D1

#3📜 EE Pre-Board March 2014📘 PowerhouseEasy

Power in a three-phase delta system with balanced load is equal to

A\(\sqrt{3}V_LI_L\,(pf)\)

B\(\sqrt{3}V_\phi I_\phi\,(pf)\)

C\(3V_\phi I_L\,(pf)\)

D\(3V_LI_L\,(pf)\)

#4📜 EE Pre-Board March 2014📘 PowerhouseEasy

What is the minimum number of wattmeters required to measure unbalanced power for a three-phase system?

A2

B4

C3

D1

#5📜 EE Pre-Board March 2014📘 PowerhouseEasy

In two-wattmeter method, the readings of the wattmeters will be identical when

Aload in one of the phases is zero

Bpower factor is unity

Cpower factor is 0.5

Dneutral is earthed

#6📜 EE Pre-Board March 2014📘 PowerhouseEasy

For an unbalanced load which connection is suitable?

A3 – wire open delta connection

B4 – wire wye connection

C3 – wire delta connection

D3 – wire wye connection

#7📜 EE Pre-Board August 2014📘 PowerhouseEasy

Two-wattmeters can be used to measure three-phase power for a

Abalanced and unbalanced load

Bunbalanced load only

Cbalanced load only

Dunity power factor only

#8📜 EE Pre-Board March 2015📘 PowerhouseEasy

For a three phase unbalanced load

AThe power factor of each phase will be proportional to the load

BThe power factor each phase will be the same

CThe power factor of at least one of the phases must be leading

DThe power factor of each phase may be different

#9📜 EE Pre-Board March 2016📘 PowerhouseEasy

In a balanced three phase wye connected circuit, the line voltages are equal

ATo the line current

BTo the phase voltage

Cand so are the line currents

Dbut the line currents are unequal

#10📜 EE Pre-Board March 2016📘 PowerhouseEasy

In a wye connected system, line current is

A0.707 times the phase current

B1.732 times the phase current

Cequal to the phase current

D1.414 times the phase current

#11📜 EE Pre-Board March 2017📘 PowerhouseEasy

The type of ac distribution system commonly used to supply both light and power is the

Aopen delta system

Bthree phase delta system

Cthree phase wye system with neutral wire

Dthree phase wye system without neutral wire

#12📜 EE Pre-Board March 2017📘 PowerhouseEasy

In a three-phase system, when the loads are perfectly balanced, the neutral current is

Azero

Bone-third of maximum

Ctwo-thirds of maximum

Dat maximum

#13📜 EE Pre-Board March 2018📘 PowerhouseEasy

For a 3-phase load balanced condition, each phase has the same value of _

Aimpedance

Bresistance

Cpower factor

Dall of these

#14📜 EE Pre-Board March 2018📘 PowerhouseEasy

In a star connected system, the current flowing through the line is

AGreater than the phase current

BEqual to the phase current

CLesser than the phase current

DNone of these

#15📜 EE Pre-Board March 2018📘 PowerhouseEasy

In a certain Y-Y system, the source phase currents each have a magnitude of 9 A. The magnitude of each load current for a balanced load condition is

A12 A

B3 A

C9 A

D27 A

#16📜 EE Pre-Board March 2018📘 PowerhouseEasy

In a three-phase system, the voltages are separated by

A90°

B45°

C120°

D180°

#17📜 EE Pre-Board March 2018📘 PowerhouseEasy

In a three-phase system, when the loads are perfectly balanced, the neutral current is

Aone-third of maximum

Bzero

Ctwo-thirds of maximum

Dat maximum

#18📜 EE Pre-Board August 2018📘 PowerhouseEasy

In a delta connected circuit of three equal resistors, when one resistor is open, the power will be

Aunaltered

Breduced to 1/9

Creduced to 1/16

Dreduced by 1/3

#19📘 EE Pocket Reviewer RojasEasy

What is the advantage of a star-connected system over a delta connected system?

AHigher current

BHigher voltage

CHigher current and voltage

DHigher power

#20📘 EE Pocket Reviewer RojasEasy

How is the power in a delta-connected system related to the power in a wye-connected system if both line current and line voltage are the same?

APower in delta = power in wye

BPower in delta = 3 times power in wye

CPower in delta = \(\sqrt{3}\) times power in wye

DPower in delta = 1/3 times power in wye

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