AC-DC

Discussion in 'General Electronics Chat' started by Lavanya.R, Apr 23, 2015.

  1. Lavanya.R

    Thread Starter New Member

    Dec 9, 2014
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    Hi All,

    Can a 1P bridge rectifier can be used to drive electromagnet?
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    What is a 1P bridge ?
     
  3. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Single phase.

    Good question since the magnetism is proportional to the rate of change of current, so its strength increases with frequency.
    The increased (doubled) frequency output of bridge applies to the ripple.

    I am not sure if the output of a plain bridge, without capacitive smoothing, can be considered all ripple.

    So I am not sure if there would be any benefit or not.
     
  4. uwed

    Member

    Mar 16, 2015
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    Sure, and the magnetic field will be quite constant even without smoothing capacitor if the coil's inductance is large (1st Maxwell: rot H = S (+dD/dt)). Of course the AC-side current will be ugly: rectangular-shaped with a lot of harmonics which might be an EMI-concern if there is some serious current involved.
     
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  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    it may cause the magnet and/ or whatever it attracts to hum and buzz but otherwise will work.
    straight 60 Hz AC is used on magnets when it is desired to lift non-ferrous metals like copper and aluminum. induced eddy currents in those metals create magnetic fields that can then be used to pick them up with the AC driven electromagnet.
     
  6. alfacliff

    Well-Known Member

    Dec 13, 2013
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    "the strength of a magnet increases with frequency"? what ever happened to inductive reactance? less ac current thorugh a coil as the frequency increases.
     
  7. Kermit2

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    Feb 5, 2010
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    yes, I believe he mis-stated the concept. INDUCED VOLTAGE will increase with increasing rate of change in a magnetic field.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    There must be literally many thousands operating at this time across N.A. for DC clutch & brakes etc.
    Max.
     
  9. Lavanya.R

    Thread Starter New Member

    Dec 9, 2014
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    Hi All,

    Thanks for your suggestion. I found a problem while testing the Rectifier ckt.
    Fuse is getting blowed up (either fuse at circuit or the fuse present in spike buster), when the circuit is been powered. what can be the reason? attached is the circuit diagram.
     
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  10. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    you have the ground connection to Negative rail, remove the ground connection,better still is to use an isolation transformer.
     
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  11. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Ditto @Dodgydave :)

    Inasmuch as it will have been abused, you may wish to verify the integrity of the diode drawn at lower-left (as per the attached schematic).

    FWIW Apprehension of the difficulty may be realized via consideration of the fact that, as connected, the lower-right diode is effectively bypassed via the G-N load center connection.

    Best regards
    HP
     
    Last edited: Apr 24, 2015
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You have a dead short to earth ground by connecting the -ve side of the bridge to ground.
    BTW a reverse EMF diode across the coil also assists in removing any ripple current through the coil and assist in retaining it at the 120Hz zero points.
    Max.
     
  13. Lavanya.R

    Thread Starter New Member

    Dec 9, 2014
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    hi all,
    Can I use output of Bridge rectifier to drive the MOSFET (supply b/n VDD and VSS) which acts as switch?
     
  14. #12

    Expert

    Nov 30, 2010
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    What is b/n?
    What do you want to drive the mosfet to do?
     
  15. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Yes -- providing that the peak output of the bridge is greater than the threshold, yet less than the absolute maximum, G-S EMF specification...
    As a practical matter, if your implementation of the MOSFET is as a switch, E(gs) must be sufficient to saturate the device at the maximum anticipated Drain-Source EMF & current...

    Best regards
    HP
     
    Last edited: Apr 27, 2015
  16. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    I've gotta guess it's "text'ease" for 'between' :D

    Best regards
    HP
     
  17. #12

    Expert

    Nov 30, 2010
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    No entiendo text-speak. :(
     
  18. #12

    Expert

    Nov 30, 2010
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    Yes, if you use the right mosfet and several other parts to accomplish switching something.
    Please post your schematic so we can see what you are trying to switch.
     
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