Transformer help

Discussion in 'General Electronics Chat' started by Chillum, Dec 7, 2014.

  1. Chillum

    Thread Starter Active Member

    Nov 13, 2014
    546
    9
    I need help choosing a transformer, the one that I'm looking at is "Toroidal Transformer, 160VA 0-35/0-35 "
    Is that 35v 4.5A?

    I have a stepdown circuit with input voltage no bigger that 37V, will this transformer exceed 37v
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,634
    2,342
    Hello,

    An 160 VA transformer of dual 35 Volts will have a current rating of about 2.25 A on each 35 Volts output.

    Bertus
     
  3. Chillum

    Thread Starter Active Member

    Nov 13, 2014
    546
    9
    and more amps with lower output? how much heat will it generate?
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,634
    2,342
    Hello,

    No, you can not draw more than 2.25 Ampere on each output.
    If you draw more current, you will burn your transformer.

    Bertus
     
  5. Chillum

    Thread Starter Active Member

    Nov 13, 2014
    546
    9
    how easy is it to build a current limiter? (and the heat question?)

    oh and won't lower voltages pull less current then
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,494
    2,364
    It is very easy to modify a toroidal transformer, either by taking turns off, adding turns or simply adding a small secondary if needed.
    In the case of the double pair windings, they are usually wound bi-filar which allows removing/reducing both windings at the same time, if needed.
    Approx: 2 turns/volt.
    Max.
     
  7. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    526
    You can use LM3xx to build current regulator.It will require heatsinks.
    After rectification and capacitors you will have 50V at the output.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,494
    2,364
    Modifiying for lower voltage = higher possible current up to the Va rating.
    What voltage are you aiming for?
    Max.
     
  9. Chillum

    Thread Starter Active Member

    Nov 13, 2014
    546
    9
    Last edited: Dec 7, 2014
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,494
    2,364
    After rectification and smoothing 30v = 42vdc (30ac x 1.414).
    As I mentioned it is comparatively easy to modify a toroidal, I have customized many in the past.
    For 37vdc a 26vac is required.
    Max.
     
  11. BReeves

    Member

    Nov 24, 2012
    412
    64
  12. Chillum

    Thread Starter Active Member

    Nov 13, 2014
    546
    9
    I'm wary of adjusting a R600 device. Not only does that power supply exceed my budget by about ZAR200, shipping is going to add another ZAR200-300, so no, not an option
    the cheaper one is withing my budget, but probably not after shipping

    FOUND IT:
    http://www.mantech.co.za/ProductInfo.aspx?Item=372M0368

    350 WATT SINGLE OUTPUT ENCLOSED SWITCHING POWER SUPPLY
    INPUT: 90-132VAC / 180-264VAC OUTPUT: 36VDC @ 9.7A
     
    Last edited: Dec 7, 2014
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,494
    2,364
    The advantage of a linear supply is it tends to be a alot more rugged and in the event it caves in it can be fixed relatively easily.
    This if you do not really need a tight regulated supply.
    Max.
     
  14. Chillum

    Thread Starter Active Member

    Nov 13, 2014
    546
    9
    ok , well other than being a switching supply, it's in my price range, it handles high amperage, it's got built in short/overload prrotection, which I can't build because heatsinks (other than cpu heatsinks) doesn't exist in cape town, so unless the switching part is really a problem, this is the power supply for me. your comments/advice please?
     
  15. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    526
    You are still going to need to adjust the voltage since its single voltage PSU.
     
  16. Chillum

    Thread Starter Active Member

    Nov 13, 2014
    546
    9
    but can't I use the switching power supply we built in wattage in resistor devider thread?
     
  17. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    526
    You can but with 30k pot.
     
  18. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,494
    2,364
    If the load varies at all significantly, NO.
    No regulation and a power waster.
    Max.
     
  19. Chillum

    Thread Starter Active Member

    Nov 13, 2014
    546
    9
    I don't know yet what my applications will be, but with the lack of heatsinks can you suggest a better solution?
     
  20. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,494
    2,364
    Why do you need to drop the voltage if the power supply has the output you need?
    Max.
     
Loading...