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Thread: LED fixtures are fusing my relays

  1. #1
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    LED fixtures are fusing my relays

    I have a gym that I set up with 20 RAB LED RAIL150W/D10 highbay fixtures, 153 watts per fixture, the fixture is rated for voltages from 100-277v 50-60hz, 0.9A per fixture, they are set up in 4 rows of 5 fixtures per row, each row is on a separate 208v single phase circuit, separately switched through a DPST ice cube relay, the relay is rated at 12A, 240, with a 120v coil.

    My problem is, I have been having a problem with arcing on the contacts as the relay opens and/or closes, seemingly excessive heat coming off of the relays and eventually getting fusing of the contacts on the relay, what could be causing this, thank you

  2. #2
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    Quote Originally Posted by Visualize79 View Post
    I have a gym that I set up with 20 RAB LED RAIL150W/D10 highbay fixtures, 153 watts per fixture, the fixture is rated for voltages from 100-277v 50-60hz, 0.9A per fixture, they are set up in 4 rows of 5 fixtures per row, each row is on a separate 208v single phase circuit, separately switched through a DPST ice cube relay, the relay is rated at 12A, 240, with a 120v coil.

    My problem is, I have been having a problem with arcing on the contacts as the relay opens and/or closes, seemingly excessive heat coming off of the relays and eventually getting fusing of the contacts on the relay, what could be causing this, thank you
    How are you feeding the coil? What voltage are you using to feed the coil?
    If you aim at nothing, you will hit it every time!

  3. #3
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    Visualize79:

    I believe it is probably a totally inappropriate application of the ice cube relay.

    Your steady-state load appears to be about 5*0.9 A, but I am not sure because you did not indicate what voltage goes to the fixture. It could be 208 or 120. However, this difference is probably not the primary problem.

    At turn on of an LED fixture there may be a very high inrush current initially charging a capacitor input filter. Possibly 10 to 20 times the steady state current. The relay you are talking about is probably a wimp for this application.

    My guess is that your problem occurs on turn on. There are various ways to minimize this current.

    You might try a GE RR relay (just a little more current capability), add some form of series impedance at turn on (reduces peak current), reduce the number of LED fixtures per relay, use a solid-state relay with adequate peak current capability, or use a much bigger mechanical relay.

    .


  4. #4
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    Thanks guys for your input, my coil input voltage is 120v, and the lights are powered with 208v single phase


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  5. #5
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    Gar, I think you're on to something with some sort of series impedance at turn on


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  6. #6
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    Quote Originally Posted by Visualize79 View Post
    Gar, I think you're on to something with some sort of series impedance at turn on


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    I think gar is right on about ice cube relays not being appropriate for your application. I don't think the answer is to mess with the lighting circuitry. I think the answer is to get a real lighting contactor.
    If you go and decide to dance with a gorilla the dance ain't over till the gorilla decides it's over.

  7. #7
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    Control relay isn't a power relay.http://www.mouser.com/ds/2/418/NG_DS...811-116991.pdf
    Last edited by sameguy; 12-30-17 at 12:18 PM. Reason: Show a relay

  8. #8
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    Quote Originally Posted by ActionDave View Post
    I think gar is right on about ice cube relays not being appropriate for your application. I don't think the answer is to mess with the lighting circuitry. I think the answer is to get a real lighting contactor.
    The problem is, I'm cramped for space, I need something that's small and really low profile, hence the 12A ice cubes, really compact, what do you think about a solid state relay, they're fairly small and easy to get at 25 amp rating, I wonder if I'd have an issue with inrush on those


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  9. #9
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    Visualize79:

    You need to study various switching devices, and various loads. You should really do some study on your own to find out the basics of how things work.

    Why are you cramped for space? Have you looked at the current to the lights at various turn on times within a cycle, the steady state current, and what happens at turn off with a scope?

    What is the VI curve for a mechanical switch contact, and for a solid-state switch?

    What is the power dissipation in a mechanical switch, and in a solid-state switch?

    What is a reasonable junction temperature for a solid-state relay?

    How does peak repetitive current of a solid-state switch relate to its current rating? What do you have to do to use a solid-state relay at its various current ratings?

    Where do you find all this information?

    .

  10. #10
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    Quote Originally Posted by Visualize79 View Post
    The problem is, I'm cramped for space, I need something that's small and really low profile, hence the 12A ice cubes, really compact, what do you think about a solid state relay, they're fairly small and easy to get at 25 amp rating, I wonder if I'd have an issue with inrush on those


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    Then use the ice cube relay as an interposeing relay and put a full sized one out where you have some space, maybe.

    I don't know how SS relays would play with LEDs. That would be something to talk to the factory about or try your own experiment with.
    If you go and decide to dance with a gorilla the dance ain't over till the gorilla decides it's over.

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