AC power/Three phase

What is the complex power?

• power at any instant of time

• average of the instantaneous power over one period

• product of the rms values of voltage and current

• product of rms voltage phasor and the complex conjugate of the rms current phasor

Calculate current (I)

• 22.3+j1.33 A

• 0.62+j0.93 A

• 1.12+0.07 A

• 0.62-j0.93 A

Reactive power is measured in

• watts

• VA

• VAR

• V

In the power triangle shown above, the

reactive power is:

• 1000 VAR leading

• 1000 VAR lagging

• 866 VAR leading

• 866 VAR lagging

In a Y-connected load, the line current and phase

current are equal.

• True

• False

In Delta -connected load, the line current and phase

current are equal

• True

• False

For the power triangle in above, the apparent

power is:

• 2000 VA

• 1000 VA

• 866 VA

• 500 VA

The instrument for measuring average power is the:

• ammeter

• voltmeter

• wattmeter

• varmeter

The average power absorbed by an inductor is zero

• True

• False

In a Y-Y system, a line voltage of 220 V produces a

phase voltage of:

• 381 V

• 311 V

• 220 V

• 127 V