Wye-delta, delta-wye configurations?

[mackeym]

I recently setup a CNC rotery phase converter, and i want to make sure the type of power output is what i need for AC brushless servo motors. I read something in the phase converter manual that said "if u need a four-wire wye voltage output, a delta-wye transformer is needed". I'm not sure what this is or if i need it. I beleve the 3-phase power from the phase converter is right, but i want to make sure before i hookup my motors. Anyone know anything about these delta-wye, wye-delta, wye-wye, and delta-delta configurations and how are they related to the input power for AC brushless 3-phase servo motors. thanks

[kreutz]

Are you planning to run the AC Brushless servo motors from the rotary phase converter directly? No servo controller in between?

[Al_The_Man]

AC brushless permanent magnet servo motors will not run off of mains three phase directly, they require commutation.
The drives convert the incoming AC to DC and then manufacture electronically the three phases and receive commutation signals from the motor.
If you are concerned about the AC power to the drives, it does not matter if the 3 phase is delta or star (Wye), as long as it is the right voltage.
Al.

[kreutz]

I asked what his intention is because I want to make sure mackeym don't damage his motors by connecting them directly to the three phase line.

[grim]

getting back to the original question, the Delta Star connected transformer provides a neutral connection from a 3 wire supply

the Delta primary consists of 3 coils all rated at the supply voltage, so in the UK that's 415V. each winding is connected directly to two input phases

The Star secondary consists of three windings rated at 240V. the starts of all three windings are joined together (forming a star point, neutral) and then the three limbs radiate out at 240V each. from one tip of the star to the next you will measure 415v

a factor of '/3 (root 3)

[mackeym]

opps. forget to mention that I'm going to use a pacific scientific sc900 series drives.

[Al_The_Man]

if you set up a RPC for these drives, then it would be equivalent to 3 phase Star connection, But without the star point being available.
But you don't need it.
You could feed these drives with either configurations, (star or delta).
The star connection normally gives you a neutral or common as Grim pointed out, which as I say, you don't need.
Don't they also take single phase? I know the SC750's do.
Al.

[mackeym]

there are different sizes...sc902, sc903, sc904, and sc905.....the sc902 and sc903 take either single or three phase. the sc904 and sc905 take only 3 phase.

[Al_The_Man]

Your RPC output should be OK as long as the voltage is within the correct limits.
Al.

[mackeym]

ok, thanks. yeah, the voltage is in the right range. this RPC has a voltage balance of 5% (CNC phase converter). I was wondering if voltage imbalance even has a large effect on performance since the drive first converts the power to DC.

[Al_The_Man]

Originally Posted by mackeym I was wondering if voltage imbalance even has a large effect on performance since the drive first converts the power to DC.

Your right, you probabally won't even notice it.
Al.