Three phase star connections

If the phase voltage of a 3 phase star connected system is 240 volts the line voltage is:

A) 415 V

B) 138.5 V

C) 240 V

D) 480 V

ANSWER: A

The angle between line voltages obtained from a star connected transformer with one phase reversed will be:

A) 0°

B) 120°

C) 30°

D) Unequal

ANSWER: D

An advantage of the star connected three phase system compared to the single phase system is: 

A) two different supply voltages are available 

B) higher line currents used 

C) less individual phase windings required 

D) lower line currents used 

ANSWER: A

If the voltage between the B phase terminal and the neutral conductor of a balanced 3 phase star connected load is 11 kV, then the voltage across the terminals of A phase and C phase is:

A) 19kV

B) 15.56kV

C) 6.35kV

D) 11kV

ANSWER: A

If the line currents to a balanced three phase 4 wire load are 10 A, the neutral current is:

A) 0 A

B) 5.77 A

C) 10 A

D) 17.3 A

ANSWER: A

In a star connected system the phase angle between line current and phase current is: 

A) 0°

B) 180°

C) 90°

D) 30°

ANSWER: A

The neutral conductor of a four wire balanced system:

A) carries no current

B) carries line current

C) carries line current times [square root of 3]

D) carries line current divided by [square root of 3]

ANSWER: A

The neutral conductor of a four wire distribution system is usually connected directly to:

A) Earth

B) A phase

C) B phase

D) C phase

ANSWER: A

The line voltage of a star connected system is: 

A) 1.73 times the phase voltage 

B) 0.5 times the voltage 

C) the phase voltage divided by 1.414

D) equal to the phase voltage

ANSWER: A

The line current drawn by a balanced 3 phase, star connected load is 25 amperes. The phase current is:

A) 25 Amps

B) 14.5 Amps

C) 43 Amps

D) 50 Amps

ANSWER: A

To obtain a star connected system it is necessary to join:

A) all the finishes together

B) the start of one winding to the finish of the next 

C) the finish of one winding to the start of the next 

D) the start and finish of each individual winding 

ANSWER: A


Last modified: Monday, 31 May 2021, 9:15 PM