Deck 10: Three-Phase A.C

Question 1

In a balanced three-phase star-connected system which has three loads, each of
Resistance 100 Ω, and a line voltage of 440 V the phase voltage is:

A) 762 V
B) 440 V
C) 311 V
D) 254 V

Answer 1

B

Question 2

In a balanced three-phase star-connected system which has three loads, each of
Resistance 100 Ω, and a line voltage of 440 V the line current is:

A) 7.60 A
B) 4.40 A
C) 2.54 A
D) 1.27 A

Answer 2

C

Question 3

In a balanced three-phase delta-connected system which has three loads, each of resistance 100 Ω, and a line voltage of 440 V the phase voltage is:

A) 762 V
B) 440 V
C) 311 V
D) 254 V

Answer 3

B

Question 4

In a balanced three-phase delta-connected system which has three loads, each of resistance 100 Ω, and a line voltage of 440 V the line current is:

A) 7.60 A
B) 4.40 A
C) 2.54 A
D) 1.27 A

Question 5

Decide whether each of these statements is True (T) or False
For a balanced three-phase supply, for the same power:
(i) Loads connected in a delta form have a higher line voltage than star-connected systems.
(ii) Loads connected in a delta form have a smaller line current than star-connected systems.

A) (i) T (ii) T
B) (i) T (ii) F
C) (i) F (ii) T
D) (i) F (ii) F