# How do 3-phase dual voltage motor windings work?

Many 3-phase motors allow for two possible line voltages, for example 230/460. I am trying to understand how the different wiring is changing the way the windings get current. I would guess that wiring for high voltage the motor would use all the windings and when wiring for low voltage it would only utilize half the windings. But, wouldn't that would give the motor different performance and draw ratings depending on how it is wired? Can someone explain how the current is traveling in both the high and low voltage wiring scenarios? Where are the poles? Thank you!

• draw in the jumpers. Commented Apr 29, 2018 at 16:43
• Why have you shown the same picture twice? Commented Apr 29, 2018 at 18:17
• so you would ask why Commented May 1, 2018 at 2:44

I would guess that wiring for high voltage the motor would use all the windings ...

Correct.

... and when wiring for low voltage it would only utilize half the windings.

Incorrect - although you could if you only wanted half power. The answer is to connect the half-windings in parallel. Note that in your second diagram T4, T5 and T8 are connected together forming a second 'Y' or star arrangement.

Then the outer terminal of each 'Y' is connected together. The Low Voltage 'YY' diagram shows T1 and T7 connected, etc.

Where are the poles?

The poles don't enter into the problem of voltage selection.

The power does not change in both cases because in the yy connection we use two coils in parallel and to simply the problem let us assume there are two resistors each one has R ohm so the power consumed will be 2*v*v/R (v is phase voltage).But in yy the v is double and R is also double so the power will be 2v*2v/2R=2v*v/R and as you see it is the same power in two cases.BUT the current in yy will be twice the current in y per phase.THE CONCLUSION is that as voltage doubled the current will be half and the power remain constant.