New build with recycled parts on a ridiculous budget 120cm*60cm work area

[Desertboy]

Yes, output is directly related to input, that is a very high input.

Will have to check Monday morning see what it reads.

[Nr1madman]

I think the voltage will drop when you connect a load on the secondary side. Now you only have the caps connected right?

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[m_c]

Assuming input voltage is at rated 230V, your output voltage open circuit is going to be at 52VAC (rated output voltage plus the regulation rating of 4%).
Multiply that by root 2, gives 73.5V peak voltage.

Now if your input voltage is at 250, which puts it around 8% above the rated voltage, so your output voltage will be proportionally higher, at 79.4V peak.

Now all you need is a sudden deceleration on a couple axes, and the energy dump back into the DC side can potentially push everything overvoltage.

If you search for my Triac retrofit thread, there's a big post there explaining all this.

[Davek0974]

Now all you need is a sudden deceleration on a couple axes, and the energy dump back into the DC side can potentially push everything overvoltage.

Thats the important bit, i would get this voltage down before connecting drives.

[Desertboy]

Have ordered a 45v 1kva which will solve the problem whilst I'm waiting I took the time to start stripping out the box and recovered some nicer wiring conduits. Also fitted a proper stop switch to it.

Friend is going to fibreglass repair the damage for me I might even paint it ;)





There's loads of space in here should I put the transformer in here as well and fit a 4 120mm pc fans two blowing in across the am882's and two sucking out the side of the transformer and leave a nice gap so the air can flow, I want to make sure the caps get good air flow over them.

It would be good to fit the transformer at the top of the box but it weighs 8kg making the box top heavy so it'll go at the bottom if i do fit I think the key will be good air flow and lots of it. I have a better on/off switch which is rated to 2hp (I think might be 3) ac3 so I think should be ok for the PSU.

[Clive S]

Have ordered a 45v 1kva which will solve the problem whilst I'm waiting I took the time to start stripping out the box and recovered some nicer wiring conduits. Also fitted a proper stop switch to it.

Friend is going to fibreglass repair the damage for me I might even paint it ;)

If you can cancel the order and reorder a 625Va as it should suite you better 45V is a good choice

[Davek0974]

None of my CNC modules get hot, i would think one fan would be ok, filtered inlet then fan with a vent at other side of cabinet.

Caps will/should not get hot or even warm.

[Clive S]

None of my CNC modules get hot, i would think one fan would be ok, filtered inlet then fan with a vent at other side of cabinet.

Caps will/should not get hot or even warm.

They won't get warm until you put a load on them. I have two control boxes the router with 4 drives does not have any fans in the box is 500x500x250 and is fine.

[Neale]

It's easy to worry about overheating but in practice, it's not a big problem on our size machines. On mine, I have two 12V fans just so that they cover a larger area and push a bit of breeze across the stepper drivers but I have wired them in series so that they run fairly slowly. Moves more than enough air. Similarly, I run the 12V spindle cooling pump on 5V and that works fine as well.

I also bought a 50V transformer for my machine (from Rapid Online), then realised that it was going to be a bit too high. Once you take into account the fact that input voltage can be some way above nominal, and the output voltage is a few per cent high to allow for voltage drop at full load, then it's easy to start nudging that 80V. In my case, I rang Rapid the day after the transformer arrived and they were happy to swap it for 45V, and even arranged a courier to pick up the old one. Good people to deal with. I'm now running at a nominal 68V which is bang on the money.

[Desertboy]

I'm going to fit a inrush current limiter ntc thermistor
https://www.ametherm.com/blog/inrush...s-got-you-down

I think this is suitable
https://www.ebay.co.uk/itm/282728849186

as far as I can tell I just wire this inline to the mains, anyone had any experience of them?