Three-Phase Delta Wye Connection

Question 1

What makes a balanced 3 Φ load?

Answer 1

Equal phase impedance and power factors.

Question 2

Which connection allows a load to see a higher voltage?

Answer 2

Delta, it will connect line to line.

Question 3

Which connection of a load results in more line current?

Answer 3

Delta, it is 3 times the line current of wye.

Question 4

What occurs when reconnecting a supply from wye to delta?

Answer 4

Output voltage is reduced by 3^1/2;

Output current is increased by 3^1/2.

(VA remains constant.)

Question 5

Why does the VA remain constant when reconnecting a source from wye to delta?

Answer 5

Because the ratings of the windings do not change;

The same concept will apply to transformers, only using ratios.

Question 6

If wye and delta loads are on the same supply, how is total line current calculated?

Answer 6

The phasor sum of each load’s line current.

(Delta line current is the phasor sum of two phase currents).

Question 7

What is the common reference used in mixed systems?

Answer 7

V_AB.

Question 8

Even though line current may be plotted on a phasor diagram, does it have a reference?

Answer 8

No.