LED MR16 Transformer Question

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Oubadah

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#116717 7-May-2013 19:40

I have some pendants that take MR16 12v halogens. Anything above 20w is too hot for the shades, but I need more light. I thought I'd try these: http://www.fetchalamp.co.nz/light-bulbs/led/philips/4241-mas65mr16wh36d.html

However, they will be below the minimum wattage rating of the existing transformers.

I was thinking of replacing the existing transformers with these: http://www.eurotechlighting.co.nz/products/ET50.html (one per three LED bulb). Is this a good strategy?

PS. one 50w per three bulb is because of locations, otherwise I could put them all on one 50w transformer.

richms

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#813199 7-May-2013 19:49

Are the existing transformers electronic or magnetic? If magnetic then it will be fine, as the minimum is just because of higher voltages at lower loads killing lamps.

Richard rich.ms

hairy1

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#813242 7-May-2013 20:33

I would say the existing transformers would be electronic and the one you linked to looks electronic as well.

Maybe get one of these

http://www.surplustronics.co.nz/shop/product-153.744.html

I am running three mr16 leds off of these and it works really well. Sorry for the lack of hyperlink. Am posting from the tablet....

My views (except when I am looking out their windows) are not those of my employer.

Oubadah

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#813294 7-May-2013 21:32

Yeah, existing is electronic.

Is there a problem with LEDs on electronic transformers even when within min-max rated wattage?

richms

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#813391 7-May-2013 23:37

With some there is. Dimming will probably not work or flicker badly.

Richard rich.ms

Niel

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#813419 8-May-2013 06:07

If an electronic transformer needs a minimum load, then it will be stated. MR16 lamps are 12V, so the electronic transformer will output 12V. The chance of it not working is very slim. Dimming should not be required as you want max light (same for us over our kitchen bench top), but the electronic transformer you've linked to in to OP is dimmable.

If you want energy efficiency (some people do), then stay away from magnetic transformers. They waste 30% in heating the core. For years now you are not allowed to retail magnetic power adapters, I would have thought the same applies to lighting but there might still be an exception. Or more exactly, you can sell a magnetic power adapter as long as it meets energy efficiency level 4 (from memory, think we are soon transitioning to 5) which is impossible with a magnetic transformer. It's been a while since I've looked at legislation, but the company I work at as been using level 5 for around 6 your now because 1) you generally get a better quality power adapter for very little extra cost, and 2) we knew it was inevitable that the higher levels will be required.

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graemeh

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#813623 8-May-2013 12:22

I have also read that you shouldn't use a magnetic transformer with LED lights because there is a power spike every time you turn the transformer off and the current can kill the LED electronics very quickly.

Oubadah

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#813850 8-May-2013 17:53

Now I'm more undecided than ever.

graemeh: I have also read that you shouldn't use a magnetic transformer with LED lights because there is a power spike every time you turn the transformer off and the current can kill the LED electronics very quickly.

I was worried about the opposite in soft starting electronic transformers, thought maybe the LEDs might bot like the ramp. However, the MR16 LED bulbs still have a lot of circuitry in themselves, would they not be able to deal with either situation?

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richms

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#813951 8-May-2013 20:22

Many dimmable electronic LED drivers will read the phase angle input and output a PWM output, which will then get filtered and ignored by any LED lamp with a driver in it, unless they are also designed to convert the PWM input into a constant current or PWM output to the LEDs inside it.

When I tried it a while back with a dimmable electronic transformer and a dimmable 12v led the results were very very messy. Magnetic was faultless.

magnetic will be allowable for lighting for a very long time as the electronic transformers high frequancy output has very strict maximum lead lengths due to RF issues. That also applies to 12v PWM output dimmable drivers that will typically make a mess out of the AM band when used with long cables, unless they run at a really low frequancy which makes them flicker like a cheap set of xmas lights.

Richard rich.ms

Niel

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#814054 8-May-2013 22:37

Those LEDs in the OP are not dimmable, so just get any electronic transformer and forget all posts about dimming or surges.

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Niel

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#814064 8-May-2013 22:42

I guess magnetic transformers will not go away for some time because we are fixated on backwards compatibility. The right solution is a new design, running lights off say 48V instead of 240V. But that discussing is heading towards OT (and will take work away from electricians).

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Oubadah

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#814853 9-May-2013 22:00

Yeah, I was never intending to dim them. The dimmable versions cost more and contain a fan (which just sounds like another point of failure if you ask me).

Philips states that those lights are "only for use with 12 V AC supply", so I guess the transformer in the third post would not have been an option anyway.

They also say:

"Please ensure installation follows the min & max load limit of the transformer, **calculated using
the halogen equivalence** (35 or 50 W) of the MASTER LEDspot LV MR16 (eg. a transformer
with min 50 W (or VA) can be used with one or more 10-50 W MASTER LEDspot LV MR16,
but is not recommended for use with the 7-35 W MASTER LEDspot LV MR16)"

So it looks like the things have definitely been designed as direct drop in replacements and I was barking up the wrong tree when I thought I should get a smaller transformer because the actual wattage of the LEDs was 19.5W (30.5W below the minimum rating of the existing transformer).

Here is the current transformer: http://www.halcyonlights.co.nz/transformers/ka150w

Should I just go for it considering this reassurance from Philips, or will it still be sub optimal and shorten bulb or transformer lifespan?

Oubadah

676 posts

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#821302 17-May-2013 18:16

Got three of the 6.5W Master LED MR16s. Turns out they work fine running the three of them off the existing 150W Halycon 'Cheetah' I also had a triple MR16 spot fitting that used those Eurotech ET50 transformers (one per bulb), so I connected one of the LEDs and it worked fine. No flicker or anything weird.

The bulbs themselves are alright, although I think I'll get 60 degree ones for the pendants next time, as the 36 degree is very focused. 36 degree was perfect for the higher spots though. The light is not as nice as the halogens, but it's better than the horrible sickly CFL light.

xlinknz

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#846603 28-Jun-2013 10:21

I just got from dx.com a 5W 12V MR16 LED to try out [as a test to replace my numerous 35W & 50W 12V Halogens] and found it flickers

The light in question is not on a dimmer so should I assume the 12v transformer isn't up to running such a low watt bulb and that is what is causing the flickering ?

This is the transformer: http://www.nzlightingltd.co.nz/shop/Transformers+12+volt+Halogen/Possum+Transformer.html

This is the bulb: http://dx.com/p/mr16-5w-500lm-3500k-5-led-warm-white-spotlight-bulb-12v-179963

I'd appreciate what I can do to resolve this so I can use LEDs

Niel

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#846941 28-Jun-2013 22:03

xlinknz: I just got from dx.com a 5W 12V MR16 LED to try out [as a test to replace my numerous 35W & 50W 12V Halogens] and found it flickers

The light in question is not on a dimmer so should I assume the 12v transformer isn't up to running such a low watt bulb and that is what is causing the flickering ?

This is the transformer: http://www.nzlightingltd.co.nz/shop/Transformers+12+volt+Halogen/Possum+Transformer.html

This is the bulb: http://dx.com/p/mr16-5w-500lm-3500k-5-led-warm-white-spotlight-bulb-12v-179963

I'd appreciate what I can do to resolve this so I can use LEDs

This says the transformer is not suitable for LEDs: http://www.electricalproducts.com.au/atco-possum-transformer-with-flex-and-plug.html

You can never have enough Volvos!