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

**Nr1madman** · 11-11-2017

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** · 11-11-2017

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** · 12-11-2017

Originally Posted by m_c

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** · 12-11-2017

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 ;)

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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** · 12-11-2017

Originally Posted by 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 ;)

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

**Davek0974** · 12-11-2017

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** · 12-11-2017

Originally Posted by 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.

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.

**Desertboy** · 12-11-2017

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?