High frequency current source lighting?

Discussion in 'LEDs and Optoelectronics' started by eem2am, Jan 8, 2013.

1. eem2am

422
0
Aug 3, 2009
Hello,

Suppose i have a load of LED luminaires that i want to light from a power supply.

I can do it with a voltage source power supply, and have current regulators connected up to the voltage bus.....................OR

I can have a high frequency (50KHz) sinusoidal AC power CURRENT source, and simply couple the led luminaires to the power bus via current transformers.

The current source way means having completely waterproof connection.........as opposed to the voltage source way, where lots of non waterproof connectors would be used.

So, do you think this is a viable proposition?.......and if so, what steps would you take to assure a good power factor in the current source bus?

2. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,839
Jan 21, 2010
Having a current source for each is the typical way of doing it.

This also means your voltage source does not need to be particularly well regulated.

3. eem2am

422
0
Aug 3, 2009
Yes thats right....but that way of doing it is less waterproof...........using a high frequency current source power bus, and coupling into it with couplers which supply the luminaires is a very waterproof way of doing it....do you not agree?

The bus wire just gets hooked into the coupler, theres no "connection" for water to run into.

4. eem2am

422
0
Aug 3, 2009
If i told you that you could get a strand of insulated wire (not coiled), make 50KHz sinusoidal current flow in it from a generator..........and then hook a resonant inductive coupler over the strand of wire, and couple 50W out of the strand of wire, and use it to light a LED luminaire with the 50W, would you say that this was feasible?

.....the coupler being 97% efficient, and from a fixed sinusoidal current flowing in the strand of wire, the coupler is made so as to produce a specific current level in the LEDs.

...so is this just boring, old , everyday stuff?, or simply not feasible?

5. JimW

59
5
Oct 22, 2010
I am not a transformer designer. But I do a fair amount of electromagnetic work. And some higher frequency transformer circuit work. And my initial thought is that this would not be close to possible. At least in any reasonable implementation.

You would be making a single wire transformer. A one wire primary (current through the wire creating the electromagnetic field) and the secondary winding making the inductive coupling. Would this create a secondary voltage? Yes. Could you get enough power transferred to power even a single 50W source? No.

I am sure that a transformer designer could give you the numbers of Amps that would have to be flowing in the single wire primary to get 3 volts at 16 Amps on the output (or some other useful combination of V/A that yields 50W). But I think it would have to be huge. Try looking for an online transformer design program and use a 1 turn primary to see if you could get anything even close to what you want. I would guess that microamp transfers are more the norm.

-Jim

6. eem2am

422
0
Aug 3, 2009
Thanks JimW..........you're saying what i've been thinking......but i'm slightly different because i've seen this thing working................i saw him hook the coupler onto the straight wire and the lamp lit up.....................it all happened quickly, and i couldnt say if it was 50W 's worth of LED light...................i'd say it wasn't.....but maybe that particular coupler was only one of their low current couplers......

On the website of the company, they have a 57W LED lamp being lit like this.....and they say that you can hang up to ten of the 50W lamps off of a straight wire if the 500W current source is used.

I wouldnt believe it, but a representative of one of our customers came in to get the system hooked up in his company so they could use it and see if they like it..i happened to know the guy, as he was an ex-boss from a previous place.........so these systems are being sent to customers now.

So i would ask, how do they get the density of flux to be so high around a single strand of wire?...................are they using special, very expensive ferrite material?

....but i speak to all about magnetic induction...............Faraday told us that we can transfer energy via magnetic fields providing there is cutting of flux.............in order to get enough cutting of flux lines, you need to get the flux lines to be dense......but how do you get dense flux around a single straight strand of wire?........the normal practice is to coil the wire so as to get the MMF up, and increase the flux density........but the "primary" here is just a straight peice of wire, so how do you get the flux to be dense enough?

Lets speak further...............imagine one of those AC current clamps that you get...where you grip it round the straight strand of insulated wire carrying AC and you measure the current in it.........well now picture something like that, where you grip it round the straight piece of wire, and then you are able to couple enough power out of the straight piece of wire to drive a 50W LED luminaire..............

.....if that seems "everyday" to you, then please tell me why?...........that is revolutionary................and i've seen it with my own eyes.

so its a question of flux density...how do you get it so dense around a straight piece of wire?

Last edited: Jan 18, 2013
7. JimW

59
5
Oct 22, 2010
I would still say no way. I don't know if it is a deliberate attempt to mislead people (a batteyr in the light module and then just a sense circuit to the wire) or if there is something else that is not being explained. But I don't believe there is anyway to couple that much power off of a single wire inductively.

But let's say or argument that it is being done. Then you would have a whole bunch of problems keeping it working. The flux density would be so high around the wire that there would be a major disruption if the wire ran next to any metal. Or if there was a lot of moisture next to the wire. Anything conductive would be a serious resistance to the current in the wire. And that would effect the lighting distributed along the wire.

But overall I doubt it is even close to possible. So there is something that is not being made clear. If you are really interested, ask the company representative for the technical information on the product. See what they are willing to put in writing.

-Jim

8. davennModerator

13,865
1,956
Sep 5, 2009
yeah but the induced current is incredibly small !

I have seen this same topic on another forum recently. dunno if it was you using a different nickname or not ??

from a single wire you would need a really high current flowing
Why do you think transformers have so many turns on the primary and secondary ?
its the only way to get the magnetic field dense enough to transfer a respectable amount of power
Yes granted, increasing the freq of the AC will improve efficiency, hence why they use hi freq's in SMPS's, it just makes the transformer smaller, but you still need a reasonable number of turns on the primary and secondary

Dave

9. eem2am

422
0
Aug 3, 2009
....they have it in writing, and on demo videos on their website...........their website is out there for all to see....but i doubt you will find it...........i tried to find it without using the company name.............and it ended up being a not so technical search term which got me there.

...that guy was my ex boss, we were amicable, but not matey, if you know what i mean...i couldnt just phone him up

......i suspect that they're using a very expensive type of super high permeability ferrite, one that keeps the field in the ferrite, or very close to it only.......

.....i said it's a single strand of wire, and it is, its a loop of wire (a short) which is connected to the output of the 50KHz sine current source.......but they twist it together so that there's not a big loop area...............

On our competitors website, it shows them literally sliding the led luminaires onto the single strand of insulated wire, and then their leds light up......with the led lamps literally lit up whilst sliding along the insulated wire.......but we twist the wire, but i think the twisting is just to reduce emc from switching harmonics of the 50khz current source.....i.e. reducing the loop area...................

i couldnt be sure if they are using the 'go' and 'return' or just the 'go'..........they certainly hook both of them in to the couplr slider, but i think they only hook both for mechanical stability..................i dont think theyd use both 'go' and 'return' as surely their fields oppose and cancel each other out?