RE: Experimenting with Auto Tap Selection for a Future Power Supply Build

three-phase — Thu, 20 Dec 2018 20:49:25 GMT

Nice project, look forward to following the build process.

[mention:b0bc65b9ecdc4307bd967592f00e340a:e9ed411860ed4f2ba0265705b8793d05] Instead of multiple tap transformer, have you considered a servo motor driving an auto transformer / variac? May need an isolation transformer upfront as well thinking about it.

Kind regards

RE: Experimenting with Auto Tap Selection for a Future Power Supply Build

shabaz — Thu, 20 Dec 2018 10:16:57 GMT

Hi John,

Excellent piece of work, and nice demo. I've been trying to give this idea some thought a while back too, and came to the conclusion that for more taps, I'd have to wind my own secondary, but that is still worthwhile doing. In many ways it complicates a PSU, but it also simplifies it, so it could still be worth it.

It is an interesting problem doing it with relays, and one I've not entirely worked out, but in a nutshell some of the issues I could see were safety related (this is not an issue for your system because you are using a single SPDT relay) to ensure that if there are more taps and relays, then a faulty relay must cause protection to kick in in the event of secondary side shorts caused by other relays switching in, and also how to reduce the relay switching current (otherwise all the relays need to be quite large). I did have a few ideas to solve these issues, but the resulting PSU would be very experimental, and not be very general-purpose, and I might need to sacrifice a few transformers for the safety tests which makes it expensive to even prototype, so for these reasons it's on the back-burner, although I wish to pursue it sometime.

It's very cool how you managed to retrofit this dual-switching system to the PSU design.