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Topic Title: Led fluorescents
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Created On: 13 April 2018 08:35 PM
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 13 April 2018 08:35 PM
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radiopotty

Posts: 33
Joined: 24 May 2016

Visited a construction site Monday and again today.Contractor had connected a string of mixed tube fluorescents and 110 volt led fluorescents to a portable 6 kva generator.The generator is not big enough for the demanded load since it supplies other equipment on the site.Mostly chop saws etc.Evedence of this is the dimming that takes place to the non led lighting when this happens. All the led lights have stopped working. My thoughts on the matter is, poor voltage regulation from the small portable generator and repeat if above with additional voltage spikes on generator restart after recovery from demand overload. Consequent rise in current demand of equipment to compensate to some extent also a factor in the fittings early demise. Am I on the right track or is there some other explanation.Certainly the fittings are not faulty by manufacture.They are working quite happily elsewhere. Any ideas or help appreciated.
 13 April 2018 11:25 PM
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AncientMariner

Posts: 840
Joined: 14 December 2004

Originally posted by: radiopotty

Consequent rise in current demand of equipment to compensate to some extent also a factor in the fittings early demise.


Gets my vote.

Take the supply voltage out of range and the current will rise in an attempt to keep the rated output power.

(Some years back needed to operate a ships radio transmitter whilst on shore power. The power supply arrangement normally was the ship's 440v 60 Hz 3-phase into a transformer and 3-phase bridge rectifier and the dc output of around 28 volts into the 750 watt RF output transceiver which used switch mode power supplies. The transformer/rectifier with a German 380 volt 50 Hz supply gave a much lower dc output voltage and the transceiver's internal switch-mode power supply, which was more than adequately rated, simply pulled more current - causing the demise of the 3-phase bridge rectifiers, which were somewhat underrated and if I remember correctly, wired in parallel.)

Clive

-------------------------
Clive S Carver GCGI IEng MIET MITP
 14 April 2018 11:47 AM
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AJJewsbury

Posts: 17079
Joined: 13 August 2003

My guess would be simple over-voltages when the generator takes time to adjust its output downwards when a load is suddenly removed, or high voltage spikes from switching operations.

Most equipment won't automatically increase current draw to compensate for lower voltages, but will simply operate at lower than it's nameplate power rating (switch mode power supplies being the usual exception rather than the general rule) . The dimming of the non-led lighting certainly suggests that the other lighting at least isn't compensating.

- Andy.
 14 April 2018 12:23 PM
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mapj1

Posts: 11074
Joined: 22 July 2004

almost certainly either the genset has automatic voltage regulation, (AVR), and the output is going unstable trying to keep up with impulsive loading from the power tools, or it does not have regulation, and as the volts take a dive the LED drivers fail to see the funny side as they try to compensate.
The well engineered fix will involve another generator, either a separate one for lights alone, or a larger one that is less upset by a bouncy load.
If it was mine and another genset was hundreds of miles away in the back of beyond, I might see if the LEDs would work off a hundred or so DC - if they did I might rectify the AC and have a reservoir capacitor in a box to hold the volts up over the dips. However I suspect this not supposed to be a tricked installation,and would not recommend such skulduggery except perhaps as a diagnostic or temporary test.

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regards Mike
 14 April 2018 08:02 PM
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radiopotty

Posts: 33
Joined: 24 May 2016

Thank you all. Nice to hear that there is a logical sane explanation .mapj1 You have brought back memories of another life. In that one I was a Mining Engineer and utilised DC lighting in intrinsically safe lighting for some situations.Ah.Happy days.
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