Power Sources and Distribution Flashcards

What is the power factor of a purely resistive AC circuit?

Answer: 1.0 (voltage and current in phase)

In a purely resistive circuit, voltage and current are perfectly in phase, so the power factor equals 1.0.

A transformer with a primary-to-secondary turns ratio of 1:2 connected to 120V AC will produce what secondary voltage?

Answer: 240V, stepping up the voltage

A 1:2 turns ratio means the secondary has twice as many turns, doubling the voltage from 120V to 240V.

What happens to capacitive reactance (Xc) as the frequency of the applied AC signal increases?

Answer: Xc decreases as frequency increases

Capacitive reactance Xc = 1/(2πfC), so reactance decreases as frequency increases.

In a balanced three-phase power system, what is the phase angle difference between each of the three voltage waveforms?

Answer: 120 degrees

In a three-phase system, the three voltage waveforms are equally spaced 120 degrees apart in the electrical cycle.

What is the primary role of the neutral conductor in a single-phase 120/240V AC distribution system?

Answer: To carry return current and establish a stable voltage reference point

The neutral conductor carries return current from loads and is bonded to ground to provide a stable voltage reference.

In a three-phase delta-connected system, what is the relationship between line current and phase current?

Answer: Line current equals phase current multiplied by √3

In a delta connection, each line is shared by two winding phases, so line current equals phase current multiplied by √3 (approximately 1.732).

In a three-phase wye-connected system, what is the relationship between line voltage and phase voltage?

Answer: Line voltage equals phase voltage multiplied by √3

In a wye connection, line voltage is the vector sum of two phase voltages and equals phase voltage multiplied by √3 (approximately 1.732).