Page 467 - Basic Electrical Engineering

a. The load is balanced
b. The load is delta connected and is balanced
c. The load is balanced, star connected, and the neutral wire is available
d. The load is balanced and star connected.

10. A balanced three-phase sinusoidal power supply means

a. Three sinusoidal voltages of the same frequency and maximum value displaced in
o
120 time phase
b. Three sinusoidal voltages of any frequency but having the same maximum value
c. Three sinusoidal voltages of some frequency and maximum value with no time phase
displacement between them
o
d. Three sinusoidal voltages of any value but having a time phase displacement of 120
between them.

11. An unbalanced three-phase supply system will have

a. Three unequal voltages
b. Three voltages having unequal time phase displacement between them
c. Three voltages of unequal magnitude and angular displacement among them
d. All of the above.

12. In the two-wattmeter method of measuring three-phase power, the reading of the two
wattmeters will be equal when the power factor of the circuit is

a. 0
b. 1
c. 0.5
d. 0.866.

13. In the two-wattmeter method of measuring three-phase power, the reading of one of the
wattmeters can be negative when the power factor angle is

a. More than 60º
b. Less than 60º
c. More than 30º
d. Less than 30º.

14. Four equal resistance of 100 Ω each connected in delta is supplied from 400 V three-phase
star-connected supply, the line current drawn will be

a. 12 A
b. 4 A
c. 6.928 A
d. 13.856 A.