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Fuse rating for electric car heating system?

Discussion in 'Power Electronics' started by dalathegreat, Dec 31, 2019.

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  1. dalathegreat

    dalathegreat

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    Dec 31, 2019
    Hi experts!
    I'm doing a fuse replacement in a power distribution module on a Nissan Leaf. This is what it looks like.
    [​IMG]

    It's a glass fuse, 32mm long. Rated for slow 30A 500VDC.

    I had my electrician father pick up a 30A fuse, but he accidentally picked one that was rated for 250VAC max. So I'm hunting for fuses. I ordered a fuse from the other side of the world, but it got me thinking how hard it is to source a high voltage DC fuse. I have some questions

    • Is it OK to use a fuse rated for 500VAC on a system that will see a bit under 400V DC max?
    • Some sources say that you should use ½ the AC rating on DC systems, any truth to this?
    • Why do manufacturers not state a DC voltage rating?
    I found ONE fuse that is stocked in my town, but it's 500VAC https://www.starelec.fi/product_info.php?cPath=66_461_487&products_id=26301 Maybe won't be enough?

    Cheers for any expertise!
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    it's a car/vehicle where is the 400V coming from ?
     
  3. dalathegreat

    dalathegreat

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    Dec 31, 2019
    Yes, the main battery when fully charged on the vehicle outputs 396V
     
  4. Hunter64

    Hunter64

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    Nov 20, 2018
    That's the problem with vintage cars, spare parts are hard to get :)
     
    Last edited: Dec 31, 2019
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    ohhh ... this is an electric vehicle ? didn't realise that from your first post ;)
     
  6. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    Looking at the picture, it looks like the fuse has tabs on both sides.
    They look more like the fuses on this page of the site you gave:
    https://www.starelec.fi/index.php?cPath=66_2536

    Keep track of the size of the fuse when you order one.

    (I can not read what is given as it is in finnish).

    Bertus
     
  7. Tha fios agaibh

    Tha fios agaibh

    2,095
    702
    Aug 11, 2014
    Pull the old fuse and look at the markings on the metal end of the fuse.

    I wouldn't use a 500v ac rated fuse for 400v dc. There's a chance it could arc over and not safety clear a fault.

    I have heard the "1/2 the ac rating" rule of thumb and although its not an accurate calculation, it seems a safe approximation.

    Manufactures don't state DC ratings on some fuses because they are not designed to interupt DC current.

    At that voltage, its best to wait for a properly rated fuse.
     
  8. dalathegreat

    dalathegreat

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    Dec 31, 2019
    Thanks for the input, I will wait for the proper 500VDC fuse to arrive in the mail!
     
  9. Bluejets

    Bluejets

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    Oct 5, 2014
    I'm curious why the fuse blew in the first place.
    Doubt there would be any 500v dc or anywhere near it being interrupted in any case.
     
  10. dalathegreat

    dalathegreat

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    Dec 31, 2019
    The PTC heater shorted out and blew the fuse. More info here https://www.mynissanleaf.com/viewtopic.php?f=30&t=30738
     
  11. bertus

    bertus Moderator

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    Nov 8, 2019

    Attached Files:

  12. dalathegreat

    dalathegreat

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    Dec 31, 2019
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