First Proper CNC Router

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Originally Posted by diycnc

I think i need to check my PSU calcs. Can someone point me towards some example PSU design calcs?
Also, any idea if there is any benefit of AC vs DC?

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There is absolutely no difference. I've built loads machines using both and see no performance or reliability differences between AC or DC.
The AC is simpler for obvious reasons so my suggestion is go with AC.

Also, 525Va transformer will do what you need. 625Va will give you a bit more overhead, which you won't need, but does increase inrush and that could give you issues with MCB trips. However easily solved with D rated MCB.

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Originally Posted by m_c

dump any regenerated energy to a big resistor

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Resistor ?

Thanks JAZZCNC. Will go with AC.

Only 70v toroidal transformer I can find is 500va, which I think should be plenty.
https://www.rapidonline.com/vigortro...-x-35v-88-0007

What size MCB would you recommend?

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Originally Posted by diycnc

Thanks JAZZCNC. Will go with AC.

Only 70v toroidal transformer I can find is 500va, which I think should be plenty.
https://www.rapidonline.com/vigortro...-x-35v-88-0007

What size MCB would you recommend?

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I pointed you to one in post #47

I went with a 10A Type D MCB in the end after trying a 6A Type D MCB that kept tripping on start up.

Note that my transformer was 750VA, 2x24v in series, (I'm running 5 steppers, with 2 steppers on X and Z) so you could try the 6A one first as they are not too expensive.

Thanks for the MCB advice. Will try 6A type D to start with.
After a little more reading, going to go for a 500va 230v primary, 2x 30v secondary. This should give me nominal 60vac when wired in series, and max voltage of 69vac when considering the mains can vary +10%, and transformer output by +6%.
A 2 x35 would give max of 81vac which is above the driver max of 80vac.

What's the recommended connectors for the high voltage wires from the PSU to the drivers?

Just been watching some of Joe Harris videos, and have had discovered the world of DIN rail connectors!
I finally understand what the rows and rows of plastic blocks are in everyone's control boxes now.

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Originally Posted by diycnc

Thanks for the MCB advice. Will try 6A type D to start with.

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Nearly always needs a 10A

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Originally Posted by diycnc

What's the recommended connectors for the high voltage wires from the PSU to the drivers?

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Directly wire from the transformer output to Fuses then to drives. Fewer connections the better. Every connection or connector is a potential problem area so fewer the better.

I guess you are referring to the fact that the psu will have a single positive cable and single negative cable output, and you need to connect these to 3 or more drivers.

Daisy chaining the drivers power input is not advised, so separate runs should be used.

Maybe Jazz has a neater solution but most people use a distribution block to connect each power output to multiple outputs, often mounted on the psu board.

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Originally Posted by routercnc

Maybe Jazz has a neater solution but most people use a distribution block to connect each power output to multiple outputs, often mounted on the psu board.

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Every connection is a potential problem down the road so if you can limit connections you eliminate potential problems. So why have connection blocks on the PSU when you can remove those connections by wiring directly to fuses.? Put the fuses on or close to PSU.

Also, note that when using AC drives your only using a Transformer so often there's no PSU board involved because you don't need Caps or Bridge.