Hello,

Suppose i have a load of LED luminaires (10 to 40W) 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?

 

LED's are DC. High speed rectifiers will be required.

Also EMC. Or you will interfere with radio and audio equipment for some distance.

And: Why?

 

...and safety

 

The rectifier is as follows.........

http://i47.tinypic.com/ws30y0.jpg

...the values of L shown are a tad higher than they really would be.

For this application, we dont care about EMC emissions, because the nature of the use is such that EMC regulatory bodies will not complain....(i cant tell all because its confidential) about it.

Also, 50KHz is very low frequency and will not radiate very well....wavelength is 6000 metres at 50KHz...so radiated emissions are not going to be bad.

The reason for this is because its waterproof, and , as you can imagine, certain "operations" take place in remote places, where it may be very wet, but lighting is still needed in the tent or whatever.....the waterproof nature is very valuable....and of course, you done really need mechanical connectors to connect magnetic fields.....so no mechanical connectors with gaps where water can get in.

 

You'll always get EMF from an AC power bus due to harmonics.

I like your idea/design. Depends on the voltage/cable length you get some loss but at 50 KHz should not be that much.

 

The current source bus should have a good power factor since there are no significant reactive components in the loop as long as the current transformers have good efficiency at that frequency.

 

The distribution wires will look highly inductive at 50 kHz and cause all kinds of problems. You will also have a small radio station going.

 

The small radio station..........i take it you mean due to harmonics?......yes ok......but sometimes, whilst on remote operations, one needs light, and the area may be wet and rainy or dripping.........so you end up putting up with your "small radio station".....because you need waterproof lighting , and you're willing to put up with whatever RF grief it puts out.

When you're on "remote operations", so to speak, the Regulatory bodies are not going to complain as they would get "told to wind their necks in".

So, you are saying that even with several LED luminaires at the secondarys of the various coupling transformers, the power factor in the current source power bus will be good?

This bus is fed from a *current source* power supply, and the inductance of the power bus surely matters not one jot?

..and safety is no concern as 50KHz electricity does not readily enough flow through the body to be able to give any kind of dangerous shock.

 

The distribution wires will look highly inductive at 50 kHz and cause all kinds of problems. You will also have a small radio station going.

If you use twisted pair wires for distribution the inductance should not be significant at 50kHz and the radiation output should be low. If it's a problem, twisted-pair shielded wire should reduce it to a negligible value.