We want 10kW of LED Lamps for our Art gallery

[zenerbjt]

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?

 

[betwixt]

Not how I would do it but it might work. You realize the bus bars would be carrying around 250 Amps - they would have to be substantial.
It would be far more economical to use standard PSUs and a circuit to detect a neutral break. Neutral failures are VERY rare!

Brian.

 

[dick_freebird]

Why not just use 120VAC commercial floods
run off wall power? Maybe take 3-phase down
to 3 single phase branches with one trio of
commercial transformers? Surplus, even, as
it's a one-off and yours to control?

Cheap as mains power is, I think it's be a real
long time before you earn back your effort
and complexity (=$). 10kW times maybe ten
hours a day run time, ten cents a kWh and
you're talking $10 a day, I guess that adds up
but will it add up, for the calendar time this
system will be used?

And if it is to be used, there's some goodness
in bulletproof big iron and cheap-as-possible
consumables (lamps) given adequate life
expectancy.

Just putting it out there - not every battle
needs fought.

 

[zenerbjt]

far more economical to use standard PSUs and a circuit to detect a neutral break. Neutral failures are VERY rare!

Thanks, I 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).

 

[FvM]

As mentioned in a previous thread of yours, circuit breakers with overvoltage trip function are off-the-shelf electrical installation components. No need to design anything yourself.

--- Updated Dec 11, 2020 ---

E.g. offered by Schneider Electric.

 

[zenerbjt]

As mentioned in a previous thread of yours, circuit breakers with overvoltage trip function are off-the-shelf electrical installation components. No need to design anything yourself.

Thanks, thought that Sollatek AVS30 has a 20ms response time...way too slow. There is nothing offtheshelf which mitigates "sudden loss of neutral". Nobody in the world does this protection function.

 

[FvM]

I believe loss of neutral could be considered a serious risk if you are located in a third world country or in the countryside. Having an urban power distribution, you should fear more realistic risks, e.g. an airplane crashing into the building.

 

[Easy peasy]

A Delta to Delta mains transformer, would obviate the need for an active PF corrector - esp if the leakage was say 4%

83 amps in each sec wdg ( = 143 A in each line ) is a bit high - but do-able

( p.s. you can put a reactor type transformer across the 3 phases + N, to bolster the neutral - it will provide neutral current in the event of a neutral loss - until the protection can kick in - obviating the need for a (much larger ) 10kVA xfmr and allowing 230Vac rated converters to be used safely)

--- Updated Dec 12, 2020 ---