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fuses not doing their job

Discussion in 'Power Electronics' started by Jbrt, Jun 10, 2019.

  1. Jbrt

    Jbrt

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    Feb 16, 2018
    I always believed that a fuse was meant to protect the electronics of an apparatus. We have had a gate motor repeatedly blow the power supply as well as other electronics. Every time the co. repairs it at great cost and then it blows again. What can I do to prevent this? Perhaps include a lighter fuse on the powerline?
     
  2. Minder

    Minder

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    Apr 24, 2015
    Use a faster sweep through (fast-blo) fuse, try the same current rating first.
    If you go too light, you could get nuisance blowing.
    M.
     
  3. Jbrt

    Jbrt

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    Feb 16, 2018
    Hi Minder, thank you for your swift reply. Could you please be more specific. You are speaking to a dummy:)
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    1,841
    Nov 17, 2011
    A fuse blows when excessive current flows. Usually that is the case when a problem in the attaches circuit occurs. The fuse does not protect the circuit from this primary failure. The fuse prevents additional damage e.g. due to fire or people from the primary fault. Changing the fuse to another than the rated value is critical. The new fuse may either blow too fast or too slow, in both cases being a nuisance and potential danger. Plus you may potentially void insurance rights if the incorrect fuse leads to additional damage.
    My advice: Use only fuses as rated. When the fuse blows over and again, have the attached circuit checked and repaired.
     
  5. Jbrt

    Jbrt

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    Feb 16, 2018
    Thanks Harald! Is there any way I can protect my electronics and power supply? I have replaced the plug with a surge charge protector; anything else I can do?
     
  6. dave9

    dave9

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    Mar 5, 2017
    More specifics needed. What gate motor and PSU, and were they meant to be mated together for this application?

    What is "blow the power supply as well as...", what exactly failed at the discrete component level?

    If the motor blows the PSU, wouldn't you need the motor replaced or choose a different PSU, not restart with the same combination that fails again and again? If you're repeatedly paying for the repair, you should insist on some warranty in writing to make them accountable for a bad result.

    A fuse blows when there is already a fault, you should alleviate if not completely eliminate the failure point rather than just fuse it differently. Perhaps a better mated fuse is eventually a good idea but it's not the primary problem.

    If you put in a perfectly sized fuse, it works, then the fault, fuse blows... if you put in a new fuse it'll just blow again, you still need to fix the fault.
     
    Last edited: Jun 10, 2019
    Harald Kapp likes this.
  7. Minder

    Minder

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    Apr 24, 2015
    Take the number of the fuse you are using and use the same current value, but fast blow, there are also very fast fuses aimed particularly at electronics, called rectifier fuses, these have a very fast sweep through so as to save the subsequent equipment in times of a surge, electrical storm etc.
    You maybe getting over-voltage surges where you are.
    How is the power managed in S. Africa?
    What is the nature of the motor, BTW?
    M.
     
  8. Jbrt

    Jbrt

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    Feb 16, 2018
    Hi Dave9, Thanks.Here is the motor (red one) https://www.niceforyou.com/sites/default/files/upload/catalogues-brochures/et500leaflet_rev_2013.pdf
    The reasons for the fuse blowing was a tree that fell on the overhead powerline; a short and power surges. 3 times the internal power supply blew. One of these times the fuse did not even blow.
     
  9. Jbrt

    Jbrt

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    Feb 16, 2018
    Hi Minder, you guys are great. I appreciate your attempts to help me.The last time I did put a fast fuse in and it still did not protect the electronics.
     
  10. Minder

    Minder

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    Apr 24, 2015
    I would also take a reading of the actual power consumed and fuse accordingly, often equip. manuf. over fuse.
    The standard here in N.A. is generally 1.5x actual peak running current.
    M.
     
  11. dave9

    dave9

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    Mar 5, 2017
    If you are stating the only reason you're having problems is power line surges, then you need a surge protection circuit. A fuse alone will not prevent a damaging level of voltage getting through to the PSU.

    However if your power is that bad you may need whole site surge protection. If you are not observing other equipment failures I would wonder if the PSU is simply low quality and cannot withstand high ambient temperatures.

    Since you did not link to the PSU I assume no specs are available and it's just want gets bundled with that motor. If all the PSU needs to do is output a fair margin over 3A @ 12VDC, you shouldn't have much trouble finding a different PSU with a more robust design. Perhaps it needs to be rated WELL above 3A for extra thermal margin, so you can stuff it in a NEMA rated weatherproof housing if the location requires it.

    I would not keep paying someone to repair something that keeps failing. Find a different option or insist on a warranty. IMO a different option is superior, warranty work can tend to get done at a snail's pace.
     
    Last edited: Jun 10, 2019
  12. Martaine2005

    Martaine2005

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    May 12, 2015
    The OP did mention trying a surge limiter device.
    I would be inclined to agree with @Minder , with a fast blow fuse. You may depend on the location that ‘any’ fuse has been fitted. That said, the OP needs to find the original fuse rating and type.
    This is for an electric gate? I think. So a fast blow fuse is unsuitable due to excess current on power up. But a good idea for initial testing.

    Martin
     
  13. bushtech

    bushtech

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    Sep 13, 2016
    "How is the power managed in S. Africa?":D
    Ask any South African here that question and he'll be taken to hospital having bust a gut laughing
     
  14. Jbrt

    Jbrt

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    Feb 16, 2018
    'If you are stating the only reason you're having problems is power line surges, then you need a surge protection circuit.' I did also mention a short (water). I put an outside power box on the wall with a surge charge plug to the gate motor, so hopefully that will stop the surge charge problem. We have had continual problems with this motor, everytime just outside the warranty period. So, perhaps time to replace it:-(
     
  15. Jbrt

    Jbrt

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    Feb 16, 2018
    Thanks Martin!
     
  16. Jbrt

    Jbrt

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    Feb 16, 2018
    :) :) :) Haha, understatement. When our power is cut off, I switch the power off at the box and wait for a while after the power goes back on before I switch it on again. All our appliances have surge charge protecting plugs.
     
  17. Minder

    Minder

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    Apr 24, 2015
    I don't agree that fast acting fuses will not protect surges.
    Years ago with the popularity of 3ph SCR bridge circuit to drive large spindle and servo motors, these were used across the line and all had rectifier (ultra-fast) fuses, in the event of electrical storms,line surges etc, it was common for one of these fuses to blow, saving what often was 50amp, 100 amp drives.'
    M.
     
  18. Jbrt

    Jbrt

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    Feb 16, 2018
    If
    Thank you I will attempt to buy an ultra fast acting fuse.
     
  19. bushtech

    bushtech

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    Sep 13, 2016
    Mantech or RS Electronics. Both will deliver but RS don't deliver to a post box
     
  20. Jbrt

    Jbrt

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    Feb 16, 2018
    Thank you Bushtech:)
     
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