H - Bridge for Electro magnetic Coil

Discussion in 'General Electronics Chat' started by rsinha, Jun 17, 2011.

  1. rsinha

    Thread Starter New Member

    Jun 17, 2011
    1
    0
    Hello Friends

    I am an Electrical Engineer and I am trying to build an H - Bridge which would drive an Electromagnetic Coil.

    My voltage requirement is around 25 V and my current requirements are 15 amps.

    Now I bought transistors 2N 3055 and MJ2955 which are NPN and PNP complement transistors. I also got IN4001 diodes to use as flybacks...

    I would appreciate if you guys could suggest a good heatsink for this application!!
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,788
    945
    Aluminum is probably the best

    It is cheap, easily workable, saws can cut it quickly and it has a very high thermal conductance.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    You might want to allow for a fan also, but it could be added after you see how warm the heatsink gets.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    The MJE2955 and 2N3055 transistors are rated for 15A maximum. You really don't want to operate them at maximum current.

    1N4001 diodes are rated for 1A continuous current. I don't know how fast you are planning on switching the H-bridge, but if it's going to be switching very fast, your diodes will likely get fried. Besides, the 1N400x series are very slow to recover; they are not very useful above 1kHz.

    You didn't specify at what frequency you plan on switching the current to this coil. Keep in mind that the 2N3055 and MJE3055 are pretty slow at switching, too. In order to function as saturated switches, they will require a considerable amount of base current.
     
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