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Discuss Fuse switch sizing for a vsd in the Industrial Electrician Talk area at ElectrciansForums.co.uk.

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  1. Lc1
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    Lc1 Regular EF Member

    Location:
    Anywhere
    Hi,
    Following on from my question about reusing a fuse switch to supply a control panel containing a vsd. The rating of the drive is 18.5kw. We will need to use a motor rated fuse. We are planning on using a 10mm cable from the switch to the control panel. My query is would a gM32m 40A motor rated fuse be too small. I believe it seems small, has anyone else came across this before?

    Thanks
     
  2. Spoon
    Online

    Spoon Trusted Advisor

    Location:
    Lancashire
    Don't they usually tell you what size fuse to use in the manual?
     
  3. Lc1
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    Lc1 Regular EF Member

    Location:
    Anywhere
    I believe so but we are at an early stage and someone else will be buying the equipment. We are just finding a supply and saying preliminary sizing based on an 18.5kw vsd.
     
  4. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Staff Member Trusted Advisor

    Location:
    Northamptonshire
    Off the top of my head 40A is probably too small.
     
  5. Lc1
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    Lc1 Regular EF Member

    Location:
    Anywhere
    Ok thanks, the next one I have found is a gM63M rating 80 Amps. Not sure if this will be oversized ?

    Thanks
     
  6. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Isn’t the cable size slightly more important at this stage?
     
  7. Lc1
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    Lc1 Regular EF Member

    Location:
    Anywhere
    Yes we have sized that at approximately 10mm. And we have identified that the existing fuse switch type CM-UT 100A-415v can be reused, Wewould like to provide an estimated protection size, motor rated fuse gM so we have something to work with.

    Thanks
     
  8. Spoon
    Online

    Spoon Trusted Advisor

    Location:
    Lancashire
    Not being funny mate, but its hard to design something when you don't have all the info.
    Best you can do is suggest a fuse size and state what vsd model you used to get the info.
     
  9. Lc1
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    Lc1 Regular EF Member

    Location:
    Anywhere
    That’s my issue it’s just generic at this stage. So I can say motor rated fuse gM63 80A. This seems overized to me though but can’t find a smaller one
     
  10. DAvid Prosser
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    DAvid Prosser Electrician's Arms

    Location:
    UK
    Doesn't the control panel come with a switched fuse isolator for the incomer ?
     
  11. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Staff Member Trusted Advisor

    Location:
    Northamptonshire
    40A may well be okay but may not. As others have stated you need hard spec from the vsd.
     
  12. davesparks
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    davesparks Trusted Advisor

    Location:
    guildford
    Surely you need to know the rating of the fuse before you calculate the cable size, not after?
     
    • Like Like x 1
  13. snowhead
    Offline

    snowhead Trusted Advisor

    Location:
    Mildlands
    A motor rated fuse is the last thing you want protecting a VSD.
    The VSD protects the motor, the fuses in the supply protect the VSD which is an electronic device.
    You need fast acting fuses as determined by the VSD manufacturer.
    I've just retired and thrown all my VSD manuals out but here's a link to an ABB VSD and the fusing required.
    Note, for a 18kw (25hp) they quote JJS50 fuse.
    PDF page 32 actual page 22
    https://library.e.abb.com/public/cb...04422cc/3AUA489002B5311_ACH400_00_UM_REVE.pdf
     
    • Agree Agree x 1
  14. MDJ
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    MDJ The Muppet Police Trusted Advisor

    Location:
    Gloucester
    Single phase or three phase? Have I missed the answer somewhere?
     
  15. Rocboni
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    Rocboni Trainee Access

    Location:
    Scotland
    ideally Semiconductor fuses req for VSD drives. Is this not taken care of in the control panel?
     
    • Agree Agree x 1
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