Register To Comment
Page 2 of 2 FirstFirst 12
Results 11 to 17 of 17

Thread: Power rails

  1. #11
    Member

    Status
    Offline
    Name
    Chris
    Robots
    Spur 4 (FW), Titus (HW) , Team Nuts
    Posts
    546
    you certainly arent going to get close to 400A with 3 TZ85A. Heck when I've smoked a TZ85 with a stalled brushless it didnt pop the 80A fuse

    10AWG is about 2.5mm2. A Maxi fuse is fine for feathers generally, a mega fuse on your setup will look big.
    I run 2 x TZ85 with 50-60 brushless on 80A fuse. its fine. I have popped a 80A fuse with 2 DeWuts but thats another story...

  2. #12
    RobotExtreme's Avatar
    Member

    Status
    Offline
    Name
    Guilherme Ferreira
    Robots
    Galactus, Rabid M8
    Location
    Lisbon
    Posts
    79
    Hi,

    REC Team is using the LITTELFUSE 150A since 2014, never had problems.
    http://pt.farnell.com/littelfuse/029...lay/dp/1354634

    But you need to take in consideration the delay characteristics of all fuses, in our case the 150A (nominal) fuse will break after 100 seconds at 150A, ~500A for 1sec and instantly (0.01sec) break with 4000A!!

  3. #13
    R9000's Avatar
    Roboteer

    Status
    Offline
    Name
    Rory Charlesworth
    Robots
    [AW] Anty-Clockwise 2 [AW] Brushless Pizza: Reheated [AW] aaaaaaaAAAAAAAA [BW] TN3PP [FW] Aegis
    Location
    Sheffield
    Posts
    544
    Thanks for your answers guys, I've ordered a 100A maxi fuse and holder, should be fine to replace my removable link too, and should end up being more well-protected. I doubt I'm ever going to be pushing more than 100A. Worst comes to the worst, I always have the stupidly big 400A to fall back on.

  4. #14
    R9000's Avatar
    Roboteer

    Status
    Offline
    Name
    Rory Charlesworth
    Robots
    [AW] Anty-Clockwise 2 [AW] Brushless Pizza: Reheated [AW] aaaaaaaAAAAAAAA [BW] TN3PP [FW] Aegis
    Location
    Sheffield
    Posts
    544
    Guess I might as well ask while I'm here - will my lifter need any kind of safety retention bar? I'm expecting not because it's quite a slow electric lifter, but I suppose it could trap your fingers if you weren't careful. There's no pneumatics or anything.

  5. #15
    Member

    Status
    Offline
    Name
    William Turner
    Posts
    18
    For a more general rule on fuses, it's not just the source of power you're protecting, it's preventing the destruction of everything downstream to the fault and causing a fire from burning off the insulation.

    In my previous job we considered about 4-5 A per sq mm of copper cable as the sensible limit, but these were very high reliability, continuous use items with a 20-30 yr service life. You could double that comfortably for short bursts. It does get a bit crazy above about 500A due to the volume vs surface area problem but I don't think many featherweights are pushing anything like that for more than a couple of seconds.

    So if you wanted to protect some 10 sq mm cable you'd aim for a fuse rating between 60A and 100A, depending on how fast a blow fuse it is, and how hot it gets in your robot. Obviously still protect the battery, but you should aim to protect the lowest rated item.

    Take a look at some tables like these below to see what I mean about current capacity:
    https://www.cse-distributors.co.uk/c...fo/table-4e1a/

    Note that although those are conservative figures for continuous use, they're also assuming a pretty big temperature rise (60deg C), I would imagine you could easily be 60deg C inside a hard working robot. Your mileage may vary.

  6. #16
    TechAUmNu's Avatar
    Roboteer

    Status
    Offline
    Name
    Euan Mutch
    Robots
    Robots: Triforce(HW) ESCS: A200S & A450S (in progress)
    Location
    Edinburgh, UK
    Posts
    301
    I would take those charts with a pinch of salt for our applications, since we are normally using silicone cables and only running for very short lengths of time. Best bet is to try running at full tilt for a realistic amount of time and check how hot everything gets.

    For example Triforce runs 6AWG silicone cable at about 400A (2x 150cc rotomax), but since it only pulls that for less than 10s it is fine, we use 2x 200A Mega fuses in parallel to protect from battery shorts.

  7. #17
    Member

    Status
    Offline
    Name
    William Turner
    Posts
    18
    Yes I completely agree take them with a pinch of salt! With silicone insulation you've just moved the tolerable cable temperatures from about 80deg C to about 160deg C. Temperature of all components is as you say the important aspect.

    My point was that you're protecting more than just the battery and the fuse should match the lowest performing thing, unless it's expendable

Register To Comment

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •