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Sourcing high voltage isolation switch for 150V @ 40A

Discussion in 'General Electronics Discussion' started by stube40, Mar 17, 2010.

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  1. stube40

    stube40

    85
    0
    Feb 9, 2010
    Any ideas who might be able to supply a high voltage isolation switch capable of handling a constant 150V @ 40A?? The Jaycar SF2245 ones I selected weren't up to the job and began to melt (I thought they might!!)

    http://www.jaycar.com.au/productView.asp?ID=SF2245&keywords=sf2245&form=KEYWORD

    I've tried all the usual suspects RS, Farnell etc. I live in QLD, Australia, but worldwide shipping is no problem.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
    2,779
    Jan 21, 2010
    This looks more like what you're after.

    The spec sheet just says 600V (currents from 40A to 125A) and doesn't specify AC or DC.

    Might be worth looking in to in more detail.

    Digikey have a great search facility, makes looking for components by parameter quite easy. Added to that, they list a vast number of components they don't stock. That too can be an advantage at times (like now, these are non-stock items).
     
  3. stube40

    stube40

    85
    0
    Feb 9, 2010
    Thanks!!.

    Steve, that switch looks great - 600V / 63A is an amazing spec for us. It even looks like it can handle the 4G cable we are using. I just ordered some stuff from Digikey on Monday - how annoying!!! I think I will order one of them as a Plan A. Now all I need is a Plan B and C...........

    We pulled the Jaycar switch apart we noted that the copper busbar (the rotary part) had welded to the 2 copper bolts. Clearly this was an issue with arcing at high voltages and hence the gap is not big enough.
     
  4. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    If the spec does not state AC or DC then it is applicable to both AC and DC.
    A word of caution from someone who has been burned. Digikey's specs are not always correct. Use the Digikey filter to locate the component. But always use the manufacturer's data sheet to make sure that the specs are what the Digikey search engine and the website says. Digikey is usually right, but sometimes they are wrong, sometimes VERY wrong.

    ---55p
     
  5. stube40

    stube40

    85
    0
    Feb 9, 2010
    Do you guys think this switch will be OK with DC then? I must admit that I was a bit wary when I read that it was a 3PST apparently designed for 3-phase.
     
  6. stube40

    stube40

    85
    0
    Feb 9, 2010
    Also, I notice this switch is a 3-pole switch - if I get the 600V / 125A version, does this mean I can put 600V/125A through each pole, or just a third through each pole?
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    2,779
    Jan 21, 2010
    55p seems to think so. I was initially of the opinion that these seemed to be for AC (mains) switching. Most switches have a lower rating for DC than AC.

    An email to the manufacturer would not go astray.

    The same for the rating per pole. Again, I would assume it's per pole, but ask anyway.
     
  8. stube40

    stube40

    85
    0
    Feb 9, 2010
    OK, I'll email them.

    I found this little beauty from Clipsal that designed specifically for DC, rated 40A max @ 250V:

    http://updates.clipsal.com/ClipsalOnline/ProductInformation.aspx?CatNo=4CB140/6DC&ref=

    It has some really nice protection/trip features internally as the attached JPG diagram demonstrates. Plus, being large volume they are quite affordable at $47.

    Admittedly, they're right on the edge of the 40A cut off I'm targetting, but the assumption here is that the C-curve associated with them will allow higher currents through for a small length of time without tripping.
     

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