60-70v unregulated power supply recommendations

[Clive S]

I just want to check that the symptoms I'm getting with my set-up is down to an inadequate power supply. Here they are:

• Losing steps on rapid travel
• Drives trip "sensorless stall detection"
• I also get an occasional message from Mach3 saying something like "one or more of the drives exceeded the 25000 kernal setting".

I've got the current settings at maximum.

I believe you are using about 36V smps at present it will be night and day difference on 70V toroidal

[Agathon]

I believe you are using about 36V smps at present it will be night and day difference on 70V toroidal

Just want I want to hear Clive.

I'm just being cautious and will look into all that Neale mentions too.

Many thanks again, David

[Clive S]

Just want I want to hear Clive.

I'm just being cautious and will look into all that Neale mentions too.

Many thanks again, David

I have given you the list in post #7 just build it any probs just ask. Its all been done before many times tried and tested. Good luck.

[Agathon]

OK, so I've built the power supply (625 VA). Ignore the overlong DC wires in the pic - I've left them long as I'm not sure where I'm going to permanently mount a fuse holder. On that topic, what size fuse should I fit for the output? The temporary set-up has a 20A fuse, but if I go with a 20mm fuse holder the largest fuse is 10A. Would a time-delay fuse work given the short peak over-current demand?

[Clive S]

You have gone to town on that. Have you fired it up to see if you are getting around 68V DC if so fine. Are you going to mount the tx on a ali back plate? Re the fuse if you are going to make a control box use din rail fuses and fuse to each drive

[m_c]

Only the input to the transformer should be fused.

Fusing the output is more likely to blow up your drivers, than protect anything.

[Agathon]

You have gone to town on that. Have you fired it up to see if you are getting around 68V DC if so fine. Are you going to mount the tx on a ali back plate? Re the fuse if you are going to make a control box use din rail fuses and fuse to each drive

I'm getting 72v DC. I wanted to mount the whole lot on an ali or steel plate, but just couldn't find anything suitable in my stock. Do you think the transformer needs to be on a metal plate? It has a rubber washer bottom and top that would frustrate any heat transfer. Most of the old Swiss machines that I deal in for a living have low voltage control systems (low current-draw of course) and they usually use Paxolin to mount all the electrics. I did think about using this as I have a large sheet, but it was just easier to use the MDF.

Only the input to the transformer should be fused.

Fusing the output is more likely to blow up your drivers, than protect anything.

Thanks, that saves me a lot of trouble.

[JoeHarris]

Only the input to the transformer should be fused.

Fusing the output is more likely to blow up your drivers, than protect anything.

Is this true!? If so I may be heading in the wrong direction! I already have fuse holders for my drives - could put Neutral Links into them I suppose and convert them into switches! or just take them off... I have seen both sides of this argument and haven't got a clue which is right...

Also when selecting fuses for the VFD and the 24v supply I'm not sure what I should be getting in terms of current or speed. Apologies - clueless.