Free Printable Three Phase AC circuits

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Three Phase AC circuits

Total questions: 30

Worksheet time: 1hrs 9mins

Name

Class

Date

Calculate the line voltage and Line current in this balanced Y-Y system:

Eline = 1.38 KV

Iline = 0.5312

Eline = 13.8 KV

Iline = 5.312 A

Eline = 7.967 KV

Iline = 5.312 A

Eline = 7.967 KV

Iline = 0.5312

Calculate phase voltage and phase current in this balanced Y-Y system:

Ephase(source) = 7.967 kV

Iphase(source) = 5.312 KA

Ephase(source) = 7.967 V

Iphase(source) = 5.312 A

Ephase(source) = 7.967 kV

Iphase(source) = 5.312 A

Ephase(source) = 7.967 V

Iphase(source) = 5.312 A

Calculate the total power consumed in this balanced Y-Y system:

1.2696 kW

126.96 W

12.696 kW

126.96 kW

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

45⁰

90⁰

120⁰

180⁰

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

zero

one-third of maximum

two-thirds of maximum

at maximum

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

Three ideal inductors are connected in star. The combination is supplied from a balanced three phase ac supply. The power consumed by the circuit will be

infinite

$\sqrt{3}\times VL\times IL\times\cos\theta$

zero

$3\times Vph\times Iph\times\cos\theta$

Three ideal inductors are connected in star. The combination is supplied from a balanced three phase ac supply. The power factor of the circuit will be...

0.5

0.866

Three practical inductors are connected in delta. The combination is supplied from a balanced three phase ac supply. The power factor of the circuit will be...

$\infty>pf>0$

$0<pf<1$

10.

Three pure resisrors are connected in delta. The combination is supplied from a balanced three phase ac supply. The power factor of the circuit will be...

$\infty>pf>0$

$0<pf<1$

11.

A three phase AC circuit is connected with 2 watt-meters to measure the three phase power consumed. It is observed that one of the watt-meter is "kicked back" while taking the reading. What will be the circuit power factor?

0.5

$0.5>pf>0$

1>pf>0.5

12.

A three phase AC circuit is connected with 2 watt-meters to measure the three phase power consumed. It is observed that both the watt-meters are giving positive reading while measuring the power. What will be the circuit power factor?

0.5

$0.5>pf>0$

1>pf>0.5

13.

A three phase AC circuit is connected with 2 watt-meters to measure the three phase power consumed. It is observed that both the watt-meters are giving equal and opposite reading. What will be the circuit power factor?

0.5

$0.5>pf>0$

1>pf>0.5

14.

A three phase AC circuit is connected with 2 watt-meters to measure the three phase power consumed. It is observed that both the watt-meters are giving equal and positive readings. What will be the circuit power factor?

$0.5>pf>0$

1>pf>0.5

15.

A single watt-meter is connected in one of the phase in a three phase balanced star connected load system. Can we measure the three phase power?

Yes

May be

Yes but with modifications in the circuit

16.

Three similar coils are connected in delta across a three phase AC supply. The watt-meter readings are 12KW & 7KW . Calculate the power input

5KW

19KW

12KW

7KW

17.

Three similar coils are connected in delta across a three phase AC supply. The watt-meter readings are 12KW & 7KW . Calculate the phase angle

4.5 degree lagging

4.5 degree leading

24.5 deg lagging

24.5 deg leading

18.

Three similar coils are connected in delta across a three phase AC supply. The watt-meter readings are 12KW & 7KW . Calculate the power factor

unity power factor

zero power factor

0.91 lagging

0.91 leading

19.

three impedances (10+j 8) ohms are connected in star across a 400 V 3 phase supply. Determine the line and phase current

18 A and 18 A respectively

10.39 A and 18 A respectively

18 A and 10.39 A respectively

31.17 A and 18 A respectively

20.

three impedances (10+j 8) ohms are connected in star across a 400 V 3 phase supply. Determine the total power consumed?

3248.66 W

9746 W

5626.94 W

16,880 W

21.

three impedances (10+j 8) ohms are connected in star across a 400 V 3 phase supply. Determine the reading of the two wattmeters to measure three phase power.

7119 W & 2627 W

7119 KW & 2627 KW

7119 W & 9762 W

22.

3 phase load consisting of three equal impedances connected in delta across a 400 V 3-phase ac supply. The line current drawn is 10A at 0.7 lagging. Determine the total reactive power.

49.47 KVAR

4.947 KVAR

4.850 KVAR

48.5 KVAR

23.

3 phase load consisting of three equal impedances connected in delta across a 400 V 3-phase ac supply. The line current drawn is 10A at 0.7 lagging. What would be the phase current if the loads were connected in star?

10 A

3.33 A

5.77A

17.32 A

24.

3 phase load consisting of three equal impedances connected in delta across a 400 V 3-phase ac supply. The line current drawn is 10A at 0.7 lagging. What would be the total active power if the loads were to be connected in star?

48.5 KW

4.85 KW

16.17 KW

1.617 KW

25.

The voltage VAB=50 $\angle$ 30 $\degree$ volts. The voltage VBA = ?

$50\angle-180\degree$

$50\angle-150\degree$

$50\angle-30\degree$

$50\angle-210\degree$

26.

when the two wattmeters used to measure a three phase power, give equal reading then the phase angle of the circuit is.

0 degree

30 degree

60 degree

90 degree

27.

A balanced three phase load consists of three coils, each of 4 ohm resistance and 0.02H inductance. Determine the total active power when the coils are connected in star. The supply is a 415 V, 50 Hz, 3-phase ac.

12.41 W

37.23 W

37.23 KW

12.41 KW

28.

A balanced three phase load consists of three coils, each of 4 ohm resistance and 0.02H inductance. Determine the total active power when the coils are connected in delta. The supply is a 415 V, 50 Hz, 3-phase ac.

12.41 W

37.23 W

37.23 KW

12.41 KW

29.

calculate the current flowing into each terminal and in each phase of the winding of a 3 phase delta connected motor developing an output of 250 hp at 2300 V between the terminals at a p.f. of 0.75 & an efficiency of 85 %

42.4 A & 24.48 A

42.4 A & 73.44 A

73.44 A & 42.4 A

24.48 A & 42.4 A

30.

For a balanced 3 phase AC system, what should be angle separation between the phases.

180 deg

90 deg

120 deg

0 deg

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Three Phase AC circuits

Total questions: 30

Worksheet time: 1hrs 9mins

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