Deck 7: Three-Phase Wye Connection

Question 1

To calculate three-phase true power, which is measured in watts, the power factor of what system must be known?

Answer 1

To calculate three-phase true power, which is measured in watts, the power factor of the AC system must be know.

Question 2

What must we examine to calculate current in the common conductor of a three-phase, four-wire wye system?

Answer 2

To calculate the current in the common conductor of a three-phase, four-wire wye system, we must examine how the currents combine from all three-phase wires.

Question 3

If all the three phases are equal, as in supplying a three-phase motor, the neutral current is the ____________________ of the three-phase conductors.

Answer 3

imbalance

Question 4

What is the star, or wye, connection particularly suited for?

Question 5

If the phase winding voltage is 120 volts, the line voltage is 240 volts.

Question 6

The formula for three-phase apparent power is line voltage x line current x ____________________.

Question 7

Current in a series circuit is not the same throughout all parts of the circuit.

Question 8

What is 208-volt, three-phase voltage used for?

Question 9

The voltage from any line to a grounded neutral is the phase winding voltage and is usually called what?

Question 10

The voltage reading across any pair of line wires in a balanced three-phase wye connection is equal to the ____________________ of the two-phase windings connected in series across the pair of lines.

Question 11

When converting from line voltage to phase voltage, divide the line voltage by ____________________ to get the phase voltage.

Question 12

The wye system provides a grounded neutral with equal voltage between each phase wire and the neutral.

Question 13

The power formula used for three-phase, wye-connected systems is not the same as that used for the delta-connected system.

Question 14

The two standard voltage patterns available from the four-wire wye system in the United States are ____________________ and 277/480.

Question 15

A single-phase power source with two hots and a neutral conductor is not the same situation as using two of the three phases of a four-wire wye and the neutral to operate a single-phase load.