using 120V drill on 240V.. Howwww??

Discussion in 'General Electronics Chat' started by camjerlams, Jun 13, 2014.

  1. camjerlams

    Thread Starter Member

    Dec 23, 2012
    56
    1
    Hi,
    I scored an American 110V Dremel 4000 (power drill) but live in Australia with 240V outlets. I realise that a step down transformer would do the job but I want to keep it nice and portable.

    The drill specifically says 110V, 50-60Hz. Not 110-240v like some appliances.

    Is there a way to modify my drill to work safely on 240V?

    My understanding is that 240V could be dangerous as it would draw twice the current because it's supplied with twice the voltage but has the same winding impedance. But the speed would be similar as the Hz is within spec. Is that correct?

    Im thinking that if the windings are capable of safely handling this current then I should just change the plug and use it. Please share your thoughts before I destroy my new toy.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,362
    Use a 2:1 step down transformer designed for that exact purpose and one that can handle the required power.
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,801
    1,105
    Only if the motor is a synchronous one, which is extremely unlikely.
    They won't be. Expect fireworks.
    You need a transformer.
     
    PackratKing likes this.
  4. camjerlams

    Thread Starter Member

    Dec 23, 2012
    56
    1
    Yeah ok.. I had a distant voice in my head saying this, I believe it's called the voice of reason, he's such a killjoy that guy.

    Thanks for the reply. It's brand new so I might try to sell on ebay instead.
     
  5. camjerlams

    Thread Starter Member

    Dec 23, 2012
    56
    1
    Thanks Mr Chips
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    You need a Tool Transformer like this..


    ok maybe this one for lower power, its a US plug dont know if it will fit an Aus socket?
     
    Last edited: Jun 13, 2014
  7. camjerlams

    Thread Starter Member

    Dec 23, 2012
    56
    1
    This bloke, DodgyDave trying to sell me his dodgy products!! :p

    Thanks Dave I didnt think step downs would be that cheap or small, Ill def. consider this
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,553
    2,375
    The Dremel is usually rated less than 2amps, so you don't need much in the way of large transformer.
    3Kva is a little over kill ;)
    They are Universal motors so they will run on AC, 50/60Hz.
    Universal motors are not frequency dependent, in fact will run on DC if not fitted with a triac controller, like the Dremel has..
    Max.
     
    Last edited: Jun 13, 2014
  9. #12

    Expert

    Nov 30, 2010
    16,313
    6,817
    Note to self: If the motor is labeled for way over 3600 RPM, it is not synchronous. If you over-volt it, it will scream like a banshee, but only for a few seconds.
     
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    Should be easy to find a "travel transformer"..
    They are commonly used when our American wives go traveling with us and think they MUST have their hair dryer from home along with 500 lbs of other crap in their suitcase. :)
     
  11. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    For a Dremel I'm guessing the actual motor takes low voltage at a couple or few amps, presumably there will be a "power-brick" type PSU which is the bit rated for 120V.

    Something that used to be very common, is mains transformers with 2 individual 110V primaries, you either put them in parallel or series to suit the local mains.

    With the 2 primaries in series, you have an autotransformer for 220V with 110V at the tap.

    The existing equipment should have a VA rating stamped somewhere - get a transformer rated about 33 - 50% more. For this application, the secondaries are irrelevant - but they're there if you think of a use for them.
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,553
    2,375
    I have essentially the same but the earlier version and it is labeled 1.12amps 120vac.
    Universal motor, triac rpm control.
    Max.
     
  13. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    How about limiting the phase control to less than 50% for use on higher voltage?

    Triac failure would be catastrophic, but a tight fuse might let the motor survive.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,553
    2,375
    Possibility, but the trick would be the limit on the triac circuit, also if the components were 240v rated?
    But a 500va 240/120 transformer could not be that much?
    Max.
     
  15. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    The selection of the triac for 120V mains probably isn't any more than absolutely necessary to withstand spikes etc.

    The safe way would be to limit the triac firing angle till after the half-cycle had peaked.
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,553
    2,375
    I meant the limit/rating on the components when using on 240v instead of 120vac.
    Max.
     
  17. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    I think the triac that was selected to work on 120V mains *might be one of the components*.
     
  18. Externet

    AAC Fanatic!

    Nov 29, 2005
    761
    57
    My Dremel 120V said AC/DC. It is 'universal' winding type.
    What would happen with a diode in series to 220VAC ?

    220VACphase---------|>|----------Dremel-------------neutral.

    Wonderful tool, lasted 35 years of heavy use.
     
  19. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,553
    2,375
    You would loose the variable speed via the triac.
    Max.
     
  20. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Are you sure?:confused:
     
Loading...