Slow blow, Anti-surge and Time delay - Fuses

Discussion in 'General Electronics Chat' started by Andreas, Sep 9, 2014.

  1. Andreas

    Thread Starter Well-Known Member

    Jan 26, 2009

    I have a 5 x 20mm glass cartridge fuse, namely T4L250V. I know that from these numbers and letters that it is a 4A, 250V AC fuse with Time delay. The L denotes low breaking capacity or glass fuse.

    But what about T4AL250V. Is the "A" just added to indicate Amps or is it to show that it is Anti-surge?

    And out of interest, is there a difference between Anti-surge, Slow blow and Time delay?

  2. MaxHeadRoom


    Jul 18, 2013
  3. Andreas

    Thread Starter Well-Known Member

    Jan 26, 2009
    I did have a look at Littlefuse's website and the information that you sent. From an academic point, it is informative and interesting but as is often the case with these documents, you rarely get a quick or simple answer. After all it's 28 pages! But thanks anyway.
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    You need to look at the "time curve" for a fuse to determine if its suitable for your application.
    Some devices have "high inrush" currents when starting and thus require a fuse that can withstand that inrush so you don't get nuisance tripping but have it still be able to provide the required protection when needed. Then some fuses you want to blow as soon as the current is at the fuse rating (or quickly right after)
    slow blow/fast blow/anti-surge,etc... all are terminology used to indicate its tripping characteristics.