24V DC from a 400V AC 3 phase mains supply - Page 1
Forum section: electronics / beginners

author: pman92
author_rank: Contributor
timestamp: April 03, 2022, 10:27:49 am
content: Hey guys,I've got an industrial machine (a "Bini" tube bender, manufactured in Australia in the 80's, for bending steel tube).Its a hydraulically operated machine, with a motor that runs from 3 phase/400v mains voltage. The machine is very simple, there is a hydraulic "directional valve" that has both an "up" solenoid and "down" solenoid to move the ram up or down when power is applied to the appropriate solenoid. The solenoids are marked 24V DC.Originally the machine was "computer controlled". It had a microprocessor based "computer" that could be programmed and stored particular bends in memory. There was a rotary encoder on the machine so it knew where the bend was at, and a limit switch to know when the ram was fully released. It had a digital readout of the current degrees of bend. The computer would control the 2 solenoids based on input from the users foot pedal, the limit switch, the rotary encoder, and what program it was running. It was really well set up for producing repeatable bends on a production line.The 3 phase/400v motor and hydraulics all still work fine. The pump starts up when you turn it on. And I've applied my own 24v DC from some car battery's to the solenoid and the ram moves up and down fine. Unfortunately the "computer" electronics no longer work. And what is left is physically damaged (I cant read any of the buttons). And there's no instruction manual on how to program it or use it.What I would like to do is remove the "computer" and fit a simple manual toggle switch (up and down). All I would need is a 24v power supply (that could supply a couple of amps) and a SPDT switch.I was going to use a commercially available 24v power supply (such as this:https://www.jaycar.com.au/mean-well-150w-24v-6-5a-power-supply/p/MP3292) but they all seem to be rated for 240v / single phase, and the machine currently doesn't have a neutral line from the mains plug so I cant access a single phase. I've also considered keeping the original transformer/power supply PCB that powered the old "computer", but I'm unsure if its working or safe and its overly complicated for what I need (it had several voltage outputs, 24v and 5v as well as some AA batteries that I assume kept the memory chips powered when the machine was unplugged so you didn't loose your programs or settings).Is there a simple, reasonably priced, and safe way of obtaining 24V DC from my 400V 3 phase mains supply?Cheers

author: JimLev
author_rank: Contributor
timestamp: April 03, 2022, 12:15:06 pm
content: Can’t you run a neutral and ground wire from the fuse/circuit breaker box so you can use the Jaycar power supply?Or just get a step down transformer to power the Jaycar?

author: Terry Bites
author_rank: Super Contributor
timestamp: April 03, 2022, 12:41:00 pm
content: I think Id be running abog standard AC-DC from a 400:230V transformer egST63/4/23Control/Isolating Transformer400VAC Input230VAC Output63VA$110.05 (nz)

author: Terry Bites
author_rank: Super Contributor
timestamp: April 03, 2022, 12:42:28 pm
content: I dont know about NZ, but in Australia thats called a criminal conspiracy!

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 03, 2022, 04:04:37 pm
content: I use something like thishttps://products.pulspower.com/en/xt40-241.htmlIt would work from 380-480V. I use it on 460V but you can use it on 400V fine.

author: Alti
author_rank: Frequent Contributor
timestamp: April 03, 2022, 04:46:27 pm
content: You could wire three 230VAC/24VAC transformers in wye, followed by a 6 diode rectifier.

author: CaptDon
author_rank: Super Contributor
timestamp: April 03, 2022, 04:53:35 pm
content: I am assuming your 400vac is line to line? You mentioned there is no neutral, so the three 230vac transformer and diodes solution would be useless. How are your mains wired?? Wye? Delta? Corner grounded? Wild leg? We need to know more however the 400vac to 230vac control transformer would work as suggested by another poster.

author: themadhippy
author_rank: Super Contributor
timestamp: April 03, 2022, 05:04:59 pm
content: 400v to 24v transformers are pretty common in industrial control panels,for examplehttps://www.ete.co.uk/product/transformer-415v-to-24v-25va-single-voltage/

author: langwadt
author_rank: Super Contributor
timestamp: April 03, 2022, 05:39:38 pm
content: Quote from: CaptDon on April 03, 2022, 04:53:35 pmwhy? just connect the three primaries in star, the center neutral is optional

author: pman92
author_rank: Contributor
timestamp: April 03, 2022, 09:13:32 pm
content: I went looking for a 400-230v transformer to use with the jaycar supply and came across this transformer/power supply (Kaleja N-S-10-B in the pictures) for a very good price.It appears to be both 230v/400v in and 24v DC out. I assume if your using 230v the connections are made between "L1" and "N1-230V", and if your using 400v its "L1" and "N2-400v".Before I hit buy it now does anyone have a reason why this wouldn't be suitable?I cant find any information on it. Can anyone confirm that the "PE" terminal is earth (I think it means protective earth)? And what the "+5%", "UN" and "-5%" are for?Cheers

author: KaneTW
author_rank: Frequent Contributor
timestamp: April 03, 2022, 09:29:30 pm
content: a) Why not run a neutral?b) These are literally commodity hardware, e.g. TRIO-PS-2G/3AC/24DC/20 for a 24VDC 20A regulated power supply from 3-phase AC

author: Brumby
author_rank: Unknown
timestamp: April 04, 2022, 09:08:36 am
content: Quote from: CaptDon on April 03, 2022, 04:53:35 pmI wouldn't have thought so.Quote from: langwadt on April 03, 2022, 05:39:38 pmThat is precisely what I was thinking.

author: CaptDon
author_rank: Super Contributor
timestamp: April 04, 2022, 02:09:29 pm
content: 400 / 1.73 = 230 so yes probably the star connection of three 230vac primaries without the neutral would be workable. I still wonder about the mains supply? Not familiar with how Aussie mains are wired. Open Delta, corner grounded delta, wild leg delta, Wye, something else I have never even seen?? 3 phase here in the states in our old factories sometimes boggles the mind. You should see the new-bies try to troubleshoot missing phases on open deltas where there is no ground reference (except for unintended leakage). Sure it's 480 3ph, "But boss, I only see 30 volts, how can that motor be running correctly?" Well.....let's go to the white board for an explanation of all the weird things you young guys are going to find in this building.

author: langwadt
author_rank: Super Contributor
timestamp: April 04, 2022, 03:13:49 pm
content: Quote from: CaptDon on April 04, 2022, 02:09:29 pmisn't the US pretty much the only one with wierd three-phase supplies? I believe AUS is just like Europe three 230(240V) hots and a neutral

author: bdunham7
author_rank: Super Contributor
timestamp: April 04, 2022, 03:35:12 pm
content: Quote from: langwadt on April 03, 2022, 05:39:38 pmIf you have a resistive or inductive load with a simple phase shift, that works nicely. Driving a non-PFC six-rectifier load through three transformers this will lead to some interesting harmonic issues. And I suspect that a PFC SMPS arrangement would not be happy either.If a neutral is not a possibility, why not just get one or three 400:24 control transformers depending on the current needed and the importance of phase balance?

author: langwadt
author_rank: Super Contributor
timestamp: April 04, 2022, 05:17:55 pm
content: Quote from: bdunham7 on April 04, 2022, 03:35:12 pmso only use two and put both primary and secondary in series

author: bdunham7
author_rank: Super Contributor
timestamp: April 04, 2022, 05:38:12 pm
content: Quote from: pman92 on April 03, 2022, 09:13:32 pmThat looks OK. I assume the +5% etc is a place to install jumpers to shim the output up and down 5%, but you'd want to dig up a manual for sure. PE will surely be ground/earth.Edit: That appears to me to be a linear (not SMPS) supply. And the 5% connector is a tap selector for the primary of the transformer. Should be very simple and work fine.

author: Zero999
author_rank: Super Contributor
timestamp: April 04, 2022, 08:24:55 pm
content: There are plenty of 400VAC to 24VDC switched mode power supplies available. I've used one a year ago, in a control box for a small three phase motor. The only issue I had was they don't do very small ones, it ended up being a bit overkill.https://uk.rs-online.com/web/p/din-rail-power-supplies/1932606https://uk.rs-online.com/web/p/embedded-linear-power-supplies/0468324https://www.digikey.co.uk/en/products/detail/cosel-usa-inc/FCA50F-24/7053045

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 04, 2022, 10:51:47 pm
content: I think the smallest 3 phase one I can get is 10A. However, I have some 5A units that operate on 380-480VAC single phase. That would do it too.