Deck 21: Power Factor Improvement

Question 1

The power factor of a load is equal to the

A) sine of its phase angle.
B) ratio of true power to apparent power.
C) ratio of its resistance to reactance.
D) each of the above.

Answer 1

ratio of true power to apparent power.

Question 2

Most industrial loads are __________ and, therefore, have ___________ power factors.

A) resistive-inductive, lagging
B) resistive-inductive, leading
C) resisitive-capacitive, lagging
D) resistive-capacitive, leading

Answer 2

resistive-inductive, lagging

Question 3

Improving; or 'correcting' power factor means to change an existing power factor so that it

A) approaches unity.
B) moves away from unity.
C) increases beyond unity.

Answer 3

approaches unity.

Question 4

The effect of a 'poor' or low power factor is causes the load to

A) draw more energy than is necessary.
B) operate below its power rating.
C) draw more load current than necessary.
D) operate less efficiently.

Question 5

The greatest beneficiary of power-factor improvement is the

A) residential consumer.
B) industrial consumer.
C) the electricity network company.
D) each of the above.

Question 6

The __________ derives absolutely no benefit whatsoever from power-factor improvement.

A) residential consumer.
B) industrial consumer.
C) the electricity network company.

Question 7

The most common method of power-factor improvement is by connecting a suitable capacitor

A) in series with the load.
B) in parallel with the load.
C) in series or in parallel with the load.

Question 8

When a capacitor is connected to improve power factor, the current drawn by the load __________, while the current drawn from the supply __________.

A) increases, reduces
B) reduces, remains the same
C) increases, remains the same.
D) remains the same, reduces

Question 9

Power-factor correction capacitors are usually rated in

A) microfarads.
B) watts.
C) reactive volt amperes.
D) volt amperes.

Question 10

The main incentive for industrial consumers to improve the power factor of their loads is

A) a reduction in the energy they consume.
B) any motors will run more efficiently.
C) they will not be subject to penalty surcharges.
D) their loads draw less current.

Question 11

It is rarely economical for an industrial consumer to improve the power factor of their load to unity because

A) of the capital cost of the necessary power-factor correction equipment.
B) their loads are not constant.
C) the cost of energy varies over time.