60-70v unregulated power supply recommendations

[Agathon]

Having thought about it, I only need to run 2 of the AM822s from a 60-72v PSU. If they are set at their maximum current what sort of VA do I need from the transformer? I'm guessing this will partly depend on the specification of the smoothing capacitors.

[Clive S]

Having thought about it, I only need to run 2 of the AM822s from a 60-72v PSU. If they are set at their maximum current what sort of VA do I need from the transformer? I'm guessing this will partly depend on the specification of the smoothing capacitors.

Some links here.
https://www.rapidonline.com/50a-brid...al-case-519318

https://www.rapidonline.com/samwha-h...acitor-11-3121

https://www.rapidonline.com/lcr-ep08...-clamp-11-3004

This has secondary of 25-25v some people like 24 - 24V
https://www.rapidonline.com/vigortro...-x-25v-88-0005

And a vid by Joe. He used 4 caps but three is fine.
https://www.youtube.com/watch?v=4OoQQg76ar4
https://www.youtube.com/watch?v=WISDqx-e23M

[Agathon]

Many thanks.

What do you think about power output. I'm running the 2 AM822s at 5.8A RMS (actually, I think that once I have the interface cable I'll programme the drives to 5.5A RMS (2.8 x 1.96) - but that's splitting hairs) so that's total RMS current of 11.6A. The AM822 manual says that 50-70% of the motor current will be sufficient.

So 2 x 5.5A = 11.0A. 50-70% = 5.5-7.7A x 70v = 385-539VA. So a 500VA transformer should be OK?

Does that sound right or should I be working with the AC output voltage of 50v?

I see that Joe used a massive 750VA transformer.

[Clive S]

Is there a reason you are using just two motors like it is a lathe?

I run 4 nema 23 on my router without problems and 3 on the mill both with 500va transformers the next one up is 625va.

Remember that the motors rarely all run at peak current together.

[GND]

And your calculations should use the AC rather than the DC voltage as the factor into the VA rating - so your figures immediately fall by a factor of 1.4! The DC output is essentially the peak value of the AC voltage, having been rectified and filtered, whereas the VA rating is RMS.

Hope that helps!
Graeme

[Agathon]

Is there a reason you are using just two motors like it is a lathe?

I run 4 nema 23 on my router without problems and 3 on the mill both with 500va transformers the next one up is 625va.

Remember that the motors rarely all run at peak current together.

It's a 3 axis mill Clive but I initially thought that I'd run the Z axis (which is just a quill with 150mm travel) with the 36v SMPS as it needs very little power. However, now that Graeme has put me right about using the AC voltage I think a 500VA supply will comfortably run all three axes. I can use the SMPS to run the 4th and 5th axes when I get round to them - happy days.

I have another problem to overcome with this machine since it has a quick-change tooling system with the tool ejected when the quill is fully retracted. There are three microswitches two associated with the normal Z- Z+ with the third setting the limit for tool ejection. I'd like to do this automatically in Mach3 rather than having to manually jog up beyond the limit switch. I'll start a new thread on this.

Thanks for all your help. Much appreciated.

I'll post some photos and maybe a video or two once I've tidied things up a bit.

[JoeHarris]

I see that Joe used a massive 750VA transformer.

Hi, for the record mine is a 625VA tx.

[johngoodrich]

hi. this is what jazz sent to me for my psu. i'm running 2 4nm nema 23's and a 8nm nema 34 and it runs absolutely fine

You'll need:
Transformer with 2 x 25V secondery coils with 625Va output.
1 x 35A 300V or higher Bridge rectifier
3 x 4700uf 100Vdc capacitors with holders.

This transformer will work.
http://www.airlinktransformers.com/c...nge/CM0625224/

This Bridge rectifier.
http://uk.rs-online.com/web/p/bridge...fiers/6296320/

Capacitors
http://uk.rs-online.com/web/p/alumin...itors/8712748/

Brackets:
http://uk.rs-online.com/web/p/capaci...clips/2035698/

if you search for it there is also a wiring diagram for it on here somewhere. all you need is very basic soldering skills and its easy to do

[john swift]

Hi John

the link to the transformer does not work
a web search for the part number cm0625224 links to

https://airlinktransformers.com/prod...ange-cm0625224

power supply circuit



I notice that data sheet for the transformer does not specify the transformer regulation (change in output from no load to full load)

the 24V output from each secondry is when fully loaded
I expect off load it could be 5 or 6% higher

in my part of the UK, depending on the time of day
the mains supply is 243 to 248 V RMS

when the mains supply is 248V
the DC power supply output can be about 77V DC off load
or 73V DC fully loaded

John

PS
with my mains supply of up to 248V
If I decided to build a power supply
I may opt for CM0625222 with two 22V outputs wired for 44V
to give me 71V DC off load

[Neale]

John - for the reasons you suggest (load regulation/mains variation), I went with a 2x45V transformer with the secondaries wired in parallel. I used a 625VA Vigortronics toroidal from Rapid Online. You could get the other components from Rapid as well and maybe get free postage. I'm using EM806 drives that are good for max of 80V and nothing's gone pop yet!

Judy a thought.