Practice Three Phase Systems In Power Applications Multiple Choice Questions with Answers Quiz-1

Q.1.

A three-phase ∆-connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 ∠30° A, what are the polar expressions for the other phase currents?

I θb = 12 ∠150° A, I θc = 12 ∠-90° A
I θb = 12 ∠120° A, I θc = 12 ∠30° A
I θb = 12 ∠30° A, I θc = 12 ∠120° A
I θb = 12∠ 90° A, I θc = 12 ∠90° A

Q.2.

In the transformer the function of a conservator is to

Provide fresh air for cooling the transformer
Supply cooling oil to transformer in time of need
Protect the transformer from damage when oil expends due to heating
None of the above

Q.3.

A balanced load is one in which all the impedances are equal.

True
False

Q.4.

A constant load power means a uniform conversion of

Mechanical to electrical energy
Electrical to mechanical energy
Current to voltage
Voltage to current

Q.5.

A single-phase sinusoidal voltage of 120 V is connected to a 90 Ω load. Current in the circuit is

13.3 mA
133 mA
1.33 A
6.2 A

Q.6.

The term 'squirrel-cage' applies to a type of three-phase ac generator.

True
False

Q.7.

A simple three-phase generator consists of three conductive loops separated by 120°.

True
False

Q.8.

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

45°
90°
120°
180°

Q.9.

Polyphase generators produce simultaneous multiple sinusoidal voltages that are separated by

Certain constant phase angles
Certain constant frequencies
Certain constant voltages
Certain constant currents

Q.10.

In a Y-connected circuit, the magnitude of each line current is

One-third the phase current
Three times the corresponding phase current
Equal to the corresponding phase current
Zero

Q.11.

In a certain three-wire Y-connected generator, the phase voltages are 2 kV. The magnitudes of the line voltages are

2,000 V
6,000 V
666 V
3,464 V

Q.12.

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

3 A
6 A
9 A
27 A

Q.13.

In a ∆-connected source driving a ∆-connected load, the

Load voltage and line voltage are one-third the source voltage for a given phase
Load voltage and line voltage are two-thirds the source voltage for a given phase
Load voltage and line voltage cancel for a given phase
Load voltage, line voltage, and source phase voltage are all equal for a given phase

Q.14.

In a Y-Y source/load configuration, the

Phase current, the line current, and the load current are all equal in each phase
Phase current, the line current, and the load current are 120° Ωut of phase
Phase current and the line current are in phase, and both are 120° Ωut of phase with the load current
Line current and the load current are in phase, and both are out of phase with the phase current

Q.15.

In a ∆-connected generator, there is a 120° difference between each line current and the nearest phase current.

True
False

Q.16.

In a Y-connected generator, there is a 120° difference between each line voltage and the nearest phase voltage.

True
False

Q.17.

A simple two-phase generator consists of two conductive loops separated by 90°, rotating in a magnetic field.

True
False

Q.18.

In a balanced three-phase load, each phase has

An equal amount of power
One-third of total power
Two-thirds of total power
A power consumption equal to (√3VL) IL

Q.19.

If in a Y-connected ac generator, each phase voltage has a magnitude of 90 VRMS, what is the magnitude of each line voltage?

0 V
90 V
156 V
180 V

Q.20.

Polyphase is characterized by two or more sinusoidal voltages, each having a different phase angle.

True
False

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