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MOSFET full bridge driving small motor question

Discussion in 'Electronic Basics' started by Joel Kolstad, Feb 28, 2004.

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  1. Joel Kolstad

    Joel Kolstad Guest

    For a MOSFET full bridge circuit driving a small AC motor (~25 watts at
    ~12V -- this is at a 50kHz switching frequency, BTW), is it OK to count on
    the body diodes of the MOSFET to carry the circulating current during the
    dead time that all the switches are off? Or should I really add discrete
    diodes in parallel with all the switches?

    ---Joel Kolstad
  2. CBarn24050

    CBarn24050 Guest

    Hi, only if you insist on running at that frequency, 15KHz should be more than
    fast enough.
  3. Jamie

    Jamie Guest

    i am trying to picture a sync motor running at 50k hz ?
    when you say dead time are you referring to regenerative
    current from the motor? if this is your worry i its not
    a problem how ever, many drives use Regen braking or some
    times called dynamic braking. it first causes a shutting of
    regen current to be drained to attempt in keeping the motor
    from load swinging or over acceleration. in some cases if the
    regen braking does not work in a defined time period a mechanical
    brake is applied.
    is it possible that your actually driving a stepping motor?
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