Results 1 to 4 of 4

Thread: Why did this Transformers fail. Is it this due to the low 230VAC rating..?

  1. #1
    Premium Member
    Join Date
    Jan 2010
    Posts
    844
    Thanks
    379
    Thanked 218 Times in 132 Posts
    Rep Power
    202
    Reputation
    2860

    Default Why did this Transformers fail. Is it this due to the low 230VAC rating..?

    Hi all,

    As you might recall I had three alarm clocks and the PS of the bar fridge fail a few weeks ago.
    I opened up the clocks and - with my level of expertise - deducted that the transformers had failed, as the bar fridge one as well.
    I'm pretty sure that the old 5KW inverter had a 'surge/peak'.

    My new 6KW unit is supplying 241VAC into the house (as I type this).

    So I borrowed a working bar fridge PS - EXACTLY - the same as my 'gone' one and thought I'd find out why, by having both powered up at the same time and comparing them side by side on the bench.

    On the working PS, the underside photo, 240VAC is present and the 'double 12VAC' pads are measuring 14 - 15VAC.
    The failed PS also has 240VAC going in but ZERO on the 12VAC.
    Only took me 5 minutes to work that out, super skills...

    So what has actually 'gone' inside the transformer?
    I understand that there are multiple copper windings [very thin]. So what has 'broken', not allowing the electricity through? A physical break, caused by what?

    A new PS is only $40. As I have already bought one anyway, I thought about finding a bare transformer, just to see if it is indeed the transformer. They cost $1 each, but I don't need 5,000qty of them...


    Why is it classed to only 230VAC? So ok to handle 240VAC continuously?
    But would a peak of eg:247VAC take it out?









Look Here ->
  • #2
    Premium Member
    Skepticist's Avatar
    Join Date
    Apr 2009
    Posts
    1,105
    Thanks
    653
    Thanked 641 Times in 506 Posts
    Rep Power
    406
    Reputation
    12200

    Default

    The primary is the 'flimsyest' winding so I'd go for an open circuit there being more likely than the secondary but an ohmmeter will prove which side is the culprit. As it's a 6VA rated transformer the primary current will be around 25-30mA max so expect a winding of around barely 0.1mm Cu being required. There's also the chance that a thermal fuse is embedded in the winding for fire protection and it's blown (not worth trying to fix it).

    The 230V rating shouldn't be a factor, ambient temperature is usually the culprit.
    Last edited by Skepticist; 13-04-19 at 06:23 PM.

  • The Following 2 Users Say Thank You to Skepticist For This Useful Post:

    GT250 (14-04-19),hinekadon (13-04-19)

  • #3
    Senior Member
    Reschs's Avatar
    Join Date
    Aug 2010
    Location
    Outside a few schooners
    Posts
    2,570
    Thanks
    536
    Thanked 1,495 Times in 756 Posts
    Rep Power
    599
    Reputation
    20198

    Default

    Definitely a thermal fuse failure.
    Cut the cover away from the mains wiring, should be the yellow tape, and you will see the thermal fuse.
    These are cheap. If there is a mains fuse, just bypass the thermal fuse.
    Last edited by Reschs; 14-04-19 at 12:34 AM.

  • #4
    Senior Member
    fromaron's Avatar
    Join Date
    Jan 2008
    Posts
    1,861
    Thanks
    147
    Thanked 437 Times in 244 Posts
    Rep Power
    300
    Reputation
    4865

    Default

    To clarify 230 Vac rating. Old standard 240 V has been changed to make Australian market more compliant to world-wide norm of 220 V.
    In fact when you see 230 Vac the device should be capable to work within -6% to +10% range. Your transformer should be able to work without problems from 216.2 V to 253 V..

  • The Following User Says Thank You to fromaron For This Useful Post:

    Skepticist (14-04-19)

  • Bookmarks

    Posting Permissions

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