LED lights. Likey to handle a fluctuating power supply?

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Nety

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#171033 2-Apr-2015 14:56

Thought this would be a good place to ask as I think we have some quite knowledgeable people about LED tech. Situation is a number of lights that are run from a generator. Currently they are all old style and work fine however there are a number of 100w standard lights and two flood lights (500w) running them all together is at the very top end of what the generator can do. So my thought is that if I can switch the 100w lights to LED's then I will be dropping the total load from ~1600w to ~1084w.
I am a bit concerned that as it is a generator and does not put out a partially stable power supply how well LED lights would cope? My expectation is that they will be needing to cope with brownouts rather then spikes.

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Dynamic

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#1276166 2-Apr-2015 15:05

Pick some likely candidates and look at their specifications for input voltage.

LED lights use a 'driver' circuit which supplies a constant CURRENT to the LED itself, not a constant voltage. I've not ever looked at situations where the voltage may fluctuate significantly, but I'm confident it won't be an issue.

I have two generators (one for work and one for home)... a cheapie 2.4kw model with a low quality output and a more expensive 800w model with a high quality digital inverter sine wave output. I am interested to hear how you get on.

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Niel

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#1276291 2-Apr-2015 18:00

If the LEDs are dimmable, then you could have fluctuations in light. If it is not dimmable, then the light output will be constant.

If it is a certified driver for the lights (i.e. sold new at a retailer, which is supposed to hold copies of compliance statements), then it is type tested to handle brown-outs and surges etc. "Type tested" means a sample was tested, but that is better than no testing. The reliability however will be similar to any other switchmode power supply, including what is in your TV etc.

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Aredwood

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#1276418 2-Apr-2015 21:21

Definitely find non dimable type LED lights. As any instability in the generator output will cause brightness variations. Also dimable types will be expecting a pure sine wave input to their driver circuits. so almost anything could happen if you feed in a non sine wave type of generator power.

Also you need to be aware of power factors when running LED lights, Fluro lights, electronic devices, basicly anything that is not a resistor. (filament lights and heating elements) From a generator or inverter. The simple way of explaining it is that most electronic devices draw power in lots of very quick bursts instead of continuously. So rule of thumb is you need to double the rated wattage of anything with an electronic power supply. When calculating loadings on generators and inverters. And depending on the type of appliance or device you might need more capacity again. Refrigerators / freezers are 1 such type.

And never plug magnetic ballast type fluro lights into any kind of inverter power supply. Either digital inverter generator, or the type of inverter that takes battery voltage and changes it into mains voltage. (The type of fluro lights that flashes and buzzes for a few seconds when you switch it on) The power factor correction capacitors in these fluro lights is what "kills" inverters. If you remove the power factor correction capacitors, You can then use fluro lights with inverters.

richms

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#1276458 2-Apr-2015 22:02

I have run several arlec twin LED worklights which were 10w a side off a tiny inverter generator, worked fine but I have had to get rid of them as they dont smooth the power supply enough so have a 50Hz flicker to them and were orange. Do that to a lesser degree when on AC power. the newer arlec ones have white lights and dont flicker on normal AC, but not tried them on a generator yet.

We put about 20 cheap no brander LEDs into a festoon string of lights, all fine off the same type of generator. Those ones seem to have a proper driver in them and no flicker at all, but they are slower to come on when on generator compared to real power. No overload or anything shows on the generator when they are starting up. LED fairy lights with a chaser do not like the generator. The controler box went pop soon after plugging in, and all the lights just went fully on all the time. No biggie since thats really what we wanted. Massive flicker in cheap fairy lights even when on regular AC so not sure if it was worse on the generator or not.

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#1276531 3-Apr-2015 00:26

richms: I have run several arlec twin LED worklights which were 10w a side off a tiny inverter generator, worked fine but I have had to get rid of them as they dont smooth the power supply enough so have a 50Hz flicker to them and were orange. Do that to a lesser degree when on AC power. the newer arlec ones have white lights and dont flicker on normal AC, but not tried them on a generator yet.

We put about 20 cheap no brander LEDs into a festoon string of lights, all fine off the same type of generator. Those ones seem to have a proper driver in them and no flicker at all, but they are slower to come on when on generator compared to real power. No overload or anything shows on the generator when they are starting up. LED fairy lights with a chaser do not like the generator. The controler box went pop soon after plugging in, and all the lights just went fully on all the time. No biggie since thats really what we wanted. Massive flicker in cheap fairy lights even when on regular AC so not sure if it was worse on the generator or not.

There are some inverters and generators out there that don't keep the same RMS to peak voltage ratios as sinewave mains. These type are fine for running resistive loads and "universal" type motors. But cause havoc with audio equipment and anything with a switchmode power supply. I suspect that these cheap inverters just output a 230v square wave. And these generators probably have a permanent magnet rotor in them. And would then have a circuit that is similar to a light dimmer to regulate the output voltage. Which works for resistive loads. But imagine trying to run electronic loads off 300V or so AC, That has been through a light dimmer to make it seem like 240V.

I own a modified square wave output inverter that does maintain the correct RMS to peak ratio. It does this by generating 340V DC internally. Then switching it with deadbands between the positive and negative voltage swings. So it runs both resistive loads. And non power factor corrected switchmode power supplies just fine. I haven't dared to try plugging in something that has active power factor correction yet.

richms

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#1276532 3-Apr-2015 00:41

I havent put a scope on my inverter generator because I dont own one, but a plug in AC power meter sits between 220 and 240 depending on what I am running, and everything I have plugged in has been happy enough. An old style fluro light did buzz a bit more, and its not powerful enough for a microwave, but no problems with anything. Even the UPS was content with it, which it was never happy with a non inverter generator which had the freq go all over the place as the engine reved up and down.

Richard rich.ms

Niel

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#1276591 3-Apr-2015 08:02

richms: The controler box went pop soon after plugging in, and all the lights just went fully on all the time. No biggie since thats really what we wanted.

We got a few of those cheap type fairy lights with controllers for our church stage backdrop, and discovered they rectify mains and have a dropped resistor (or was it series capacitor at the AC side?) For 240V applications vs. 120V, then the circuitry for sequencing. Virtually no surge/spike protection, and the voltage that comes out of the controller box onto thin single insulation wires to the LEDs is around 95V or so. (BTW I've shorted out the driver transistors so the LEDs are always on irrespective of the controller does.) They do not comply with NZ safety standards (probably only USA 120V standards), recommend you find ones which state they use a 24V transformer for example from http://www.partylights.co.nz/

If this is a permanent installation, then I'd suggest looking into a system that charges a battery and drive LEDs off that without stepping up to mains and then back down to LED voltage. This can be done with light fittings which has external drivers, you don't use the 240V driver but a battery driver instead. LED light fittings run off approximately 32V (actually 300mA constant current, so 10W needs about 30V). Sounds complicated, but very easy and not expensive and running off a safe voltage and reliable.

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