Non EV LED Lighting PSU Question

[NeilP]

Not EV related... except if you were to say that if my lathe had better lighting, my next hub motor axle might be more accurate !


Ok, so I have a Colchester Triumph 2000 lathe.
British mains 3phase power,
The power socket and cable is 4 pin, being 3 phases plus Earth. No neutral.

I cannot run a neutral line from fuse board/distribution panel

So that means I cannot get a standard 240 volt household supply from it.

The original lathe lighting unit takes two of the phases, feeds them in to a straight Primary|Secondary transformer to give a 50VAC supply
The original light bulb was a standard bayonet fit light bulb..., but in 50 V format
A horrid yellow incandescent light that is crap to work by
Yes, I could just run an extension lead from a normal 240v ac socket and run a new light off that...But that is way too easy


Anyone any ideas how I can utilise the 50VAC to run some LED lights, spot lights at the lathe cutting head?

 

[Hwy89]

Four 12 V automotive LED lights in series. Don't worry about the AC they will be self rectifying.

 

[NeilP]

Quick and simple, cheers

My mind was chucking around ideas full of bridge rectifiers, capacitors, Switched mode supplies, voltage convertor boards off of E-bay, 3-d printed cases, hours of stress building , experimenting , cursing and swearing.

And you come along and solve the problem with one quick simple and easy solution.

Most disappointed

 

[Balmorhea]

There are many nominally 12V chip-on-board (COB) LEDs available, in several different colors of white light. As discrete components, these can be shockingly cheap, and the broad wash of light they put out is useful as task lighting.

I assume your 50V supply is AC. If you use a bridge rectifier and a big smoothing capacitor, you'll end up with something closer to 70VDC. That means six 12V LEDs in series will work well, and without significant flicker.

You can mix different color temperatures of white light to improve the overall section [edit: spectrum] and color rendering.

 

[NeilP]

Yes, AC,
Measured at spot on 50AC with cheap DVM

YEP, understand the RMS values etc and 70 v bc when rectified.

Will start searching online for suitable 12v lighting units. Thanks


Next issue...
The lathe has a Newall Spherosyn digital readout/encoder unit that runs off 240 vac.

The lathe supply does not have a neutral so I can’t just take a single phase, neutral and earth to get a 240 volt standard feed,
That is a pain as I need a 240 vac feed to run Newall encoder. Yes, of course, just run an extension lead... but would be nice to get a 240v out of this too... any ideas? Only needs 3 amp max

 

[amberwolf]

You could wind a transformer (if you can't find one) with the right ratio for 50:240 (1:4.8).

But...3A at 240V is over 700W. What is in that encoder that takes that much power?

Can the 50V transformer winding put out that much power? It would need to be over 14A on the 50v side.

 

[NeilP]

Sorry, absolute Max would be 3 amp, simply because it has a 3 amp fuse in its standard UK 3 pin plug. As you say, probably much much less. Was somewhere between 2-5 in the morning, on the phone from bed when I wrote that. So yeah, much lower,, sub 1 amp if not less

Yes, transformer, that did occur to me.

As did the possibility of seeing what the other unused tapping on the 50V transformer do. Might strike lucky ...

Right, coffee, shower and off to motorsport event

Thanks

 

[minimum]

What is the DRO input voltage? Maybe you can switch transformer to one that accepts 300-500VAC.
If it's 12VDC (or close) then you could run your lights off it as well, assuming it's power output is enough.
Here's selection of DIN rail mountable that should work. Just pick right voltage/power.

 

[NeilP]

It is 240 vac input

Have been looking at other transformers

https://www.ete.co.uk/wp-content/uploads/2016/10/WV.pdf

Think if I got a 380 In 240 out, I could then run any lights with a 12v Switched mode type supply, and run the Digital display too

 

[minimum]

It is 240 vac input

It's the DRO's power supply that has 240VAC input. DRO itself is most probably either 5 or 12VDC in. That's the DRO's PSU output that counts.

 

[minimum]

I just checked the DRO manufacturers website. All their models accept 15-24VDC ±10%

So 15-24VDC PSU that has input range around 400VAC would do. You could use MR16 socket "halogen replacement" LED bulbs off it as well without problems as long PSU power rating is up to it.

 

[fechter]

What do you get if you measure between 2 phases of the 3 phase supply? Between phases will be single phase.

 

[NeilP]

I just checked the DRO manufacturers website. All their models accept 15-24VDC ±10%

The newer ones maybe, but I just popped into the workshop, and it only had the standard ‘IEC’ type 240v ac input kettle style plug, there is no other input jack socket
Just says 110/240v 18VA
So I have ordered a 100VA 380-240 volt transformer from the website I linked to earlier.

 

[NeilP]

What do you get if you measure between 2 phases of the 3 phase supply? Between phases will be single phase.

400 volts. Was
To get standard 240 volts I need the neutral line too.
Think in USA your single phase might be across two phases of your 3 phase, but over here we need the neutral to get down to 240
All our standard household sockets are 240 V

 

[john61ct]

Yes, many devices compatible with standard (international) Single Phase 220-240V, will **not** work with American 220-240V Dual Phase (aka Split Phase)

https://www.bluesea.com/support/articles/AC_Circuits/87/Differences_in_USA_and_European_AC_Panels

For anything expensive / significant I look for "universal" world power compatibility input, but I believe that's all Single Phase gear.

 

[NeilP]

 

[NeilP]

Have ordered a 100VA 380-240 transformer

Would have liked bigger, but want to fit in existing box if I can

Encoder is 18 VA
Looking up LED lighting strips and swan neck units now

 

[NeilP]

OK, so I ordered one of these..

https://www.ete.co.uk/product/transformer-415v-to-240v-25va-single-voltage/

and it arrived.
Tested it out, but because it is a transformer and its no load voltage being higher until load is drawn ..it is useless for me....bugger.

Its no load output is 267 volts. Sticking that voltage up an expensive DRO is not login to be a good idea...

bugger

any one else know of a way to get a nice regulated 240 vote supply from a 415 volt input.


small load requirement.

18 VA..so what 22 Watt...91mA for the DRO, and maybe 150 - 200mA for the two LED lighting units. 300Ma total load at 240 volts from 415 input

 

[marty]

Next issue...
The lathe has a Newall Spherosyn digital readout/encoder unit that runs off 240 vac.

Why not play electrician and put a outlet on the wall near the lathe? Kill two birds with one stone. Outlet could power your digital readout/encoder gadget and a nice new light for the lathe. Hanging light over the lathe? Floor, desk, or machine, lamp?

 

[NeilP]

Already have enough 240 volt outlets on the wall, That is how we currently do it.

Just wanted to get it all running off of one single feed.

Alternatively I could run a new 5 wire three phase supply, to bring a neutral to the machine as well to give direct 240. But was trying to do it with as little building wiring as possible

Multiple other ways it could be done.

 

[Skorohod]

Its no load output is 267 volts
any one else know of a way to get a nice regulated 240 vote supply from a 415 volt input.
small load requirement

You can force transformer to behave by connecting 22k resistor as load. That may give you about 240^2/22000 = ~2.6 Watts of heat dissipation on resistor.

 

[NeilP]

Ah yes, nice idea
Thanks
Will try that when I get home
Should of thought of that myself, as an extension to my own thoughts. I was thinking I need to load it with a bulb or make sure to power in other stuff first

Got plenty power resistors kicking about

 

[Punx0r]

Since the 240V socket is ring next to the 415V 3 phase socket I think I would have just cable tied a 240V flex to the 3 phase machine lead and plugged both into the wall :wink:

For what it's worth, LEDs on 50Hz AC supply have a noticable flicker so I think you've gone the right way converting to DC.

Another possible route might have been to run the 50VAC straight into a dc-dc converter to drop to 12VDC (50:50% chance it'd work without rectifying first) to run the lights, and open up the DRO as I bet there's a little 240VAC - 12VDC transformer & rectifier inside.

 

[NeilP]

Since the 240V socket is ring next to the 415V 3 phase socket I think I would have just cable tied a 240V flex to the 3 phase machine lead and plugged both into the wall :wink:

That is how it is at the moment, but was just trying to get it all running off one.

 

[Punx0r]

Fair enough! I guess I'm more a believer in the best permanent fix is a temporary one