Mians transformer to power 10kW worth of LED lamps?

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opampsmoker

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Hello
We have a big indoor art gallery. Its a house full of art displays, each one will be lit up by a led lamp. Each LED lamp is about 40W continuous. There are 250 of the lamps. As such, the total power needed is 10kW.

We don’t want to use offline SMPS based LED drivers. This is because if the neutral gets accidentally disconnected from the upstream 3 phase supply, then the phase-to-neutral voltage may go up to 587Vpk, and this will blow up any offtheshelf Offline SMPS based LED driver. Therefore, we wish to use a 10kW, 3 phase mains 50Hz transformer, which steps down to three phase 40VAC outputs. We will then run this 40VAC along busbars…..then, we will use 250 simple 3phase, 6 pulse rectifiers. This will give us an approx. 55VDC output from which we can run the 250 SMPS based non-isolated LED drivers of 40W each…to feed each lamp.

My question is..

What do you think the efficiency will be? We believe we can get a 3 phase 10kw mains transformer at 99% efficiency custom built for around 10,000 pounds. Is this correct? Also, we will put an 10kW Active harmonic filter upstream of the three phase transformer to correct the power factor. What will the overall efficiency be concerning the Active harmonic filter and the three phase transformer?

We believe we can buy the Active Harmonic filter offtheshelf for £4000. Would you agree?
 

yes, it sounds perfect. Maybe buy an extra set - you wouldn't want all that art to be in the dark in case of an equipment failure. Be careful how you wire it up, it could all go kablooy if you lose connection to neutral.
 
If anything, you might want a "3-phase" transformer similar to what's found in section 500 here https://www.vesco-usa.com/CV-8_Manual.pdf#page=113

This one generates aprox 15 kVDC at 1.5A and the transformer is BIG. Three phases are applied to the primary and you get a single DC out eventually. It's about 30 kW as well.

There are 3 phase protection devices for motors. My favorite was MotorSaver

Distributed sounds better than a bucket of Amps in one place.

One system was 6.3 VAC at 3000 A. That was distributed as a buss bar.
 
So you're looking at spending UKP14,000 to illuminate 250 items. That's UKP56 per item!! Can you not buy a good LED flood light that will do the job for less that UKP56?

Mike.
 

You've yet to produce any reason why you imagine this might be so? - and even if it was (which I doubt) why would you even consider such a completely unlikely event?. Why are you even involved at this level?, an electrician will presumably be fitting the lights?, and will certainly have no such concerns.

Have you ever tried a 40W LED lamp? - assuming you mean a flood light?, it's INCREDIBLY bright - you can't look at it from anywhere close.
 
Thanks, i appreciate they are bright. I also appreciate loss of neutral is rare…..but its an absolute decree that our system can handle it…no choice for us there. They already tried it with loads of offtheshelf offline SMPS’s which powered all the lamps….and then they activated “loss of neutral”, and the whole installation burned down. They will not consider offtheshelf offline PSU’s again.

We could design our own offline SMPS’s with comparator circuitry and FET switches which simply switch out the input voltage when loss of neutral occurs, but this would be expensive.

There are literally no offtheshelf devices which mitigate the sudden rise in voltage that occurs with loss of neutral (as attached LTspice shows loss of neutral).
 

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BTW. Are you 3 phase Y, 3 phase delta or 3 phase hi-leg delta? What voltage?

In the US, we had the building loose a phase in a Y system. 460, I think, or 208 was affected.
A friend lost a neutral in his house 240/120 split phase.
 
KeepItSimpleStupid said:
BTW. Are you 3 phase Y, 3 phase delta or 3 phase hi-leg delta? What voltage?
Click to expand...
Normal UK power is 240 V phase to neutral, 415 V between phases. Single phase loads can be 240 V or 415 V. Some three-phase loads use the neutral, some don't. A three-phase motor with a Y connection wouldn't normally have the star point connected to neutral.

UK domestic supplies are almost always single phase, 240 V, so just one the three phases.
 
10 kVA transformers don't cost much more to get one made the way you want over the cost of an off-the-shelf one. There are companies that have the laminations, bobbins, enamelled wire and the knowledge and equipment to put a transformer together to your requirement quite quickly and at a reasonable cost.

https://www.transformers.uk.com/three-phase-transformers is one such supplier.

Alternatively you could buy a few of these:-

https://uk.rs-online.com/web/p/din-rail-panel-mount-transformers/0482651/ or similar

which can be wired for 415 V input so that no neutral connection would be needed.

I agree that you need and engineer who is familiar with industrial supplies.
 
I didn't know they were made: https://www.lovatoelectric.com/Mini...and-incorrect-phase-sequence/410005010005/spd

3 phase protection with neutral loss protection

Our building did loose a phase once. There were 36 heat pumps using 3 phase 460 and only one or 2 motors died/ They were not the problem.

What was the problem is we had three chillers that were replacements for liquid nitrogen systems. A compressor in one of those chillers died. I think the cost was like $10,000 USD to fix.

The other was a special vacuum pump called a roots blower. I think that was about $5000.0 USD to repair. This blower did have a thermal that could be incorporated into the shutdown.

I ended up specifying that 5 systems be fitted with phase protection. There was a "tripping delay" and a "restart delay: that could be set. Cost of the boxes made by Motor Saver were < $150.00 ea.

One vacuum pump, I did differently. Many of our vacuum systems used the same pump, single phase 208V. We worked on a spare.re-build principle. When a pump died, we swapped in a previously re-built spare. The vacuum connectors and power were eventually standardized.

One system used a 3 phase 208 pump with no spare. That disconnect could easily be configured to handle a 208 single phase oump.
 
Yet again;
You have three phase power.
DO NOT USE NEUTRAL - get appropriate parts and run everything between phases. @ 415 or so.

If you must use 230V lighting, you can get 1 KVA 415 > 230V transformers retail for around 100- each; less in quantity.

Use sets of three with the primaries in delta to balance the loads.
No neutral, no changes with loss of "neutral" at the supply.

Worst case with any input disconnection is some light dim or go out.
 
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