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TVS "diode" before and after H-bridge?

Discussion in 'Electronic and hardware generally' started by xytras, Mar 28, 2017.

  1. xytras

    xytras Member Gold Contributor

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    I wonder if it makes any sense to put a TVS before and after my H-bridges.
    As I burned one of the IMS-1 and want to replace that with an IMS-2C, which just arrived, I want to make sure I am not blasting it to hell again. But I am not sure if a back-EMF or a peak from the PSU (while switching on/off) killed the IMS-1 so I was wondering if it does make any sense to put the TVS like that:

    - ----|-------|--------|------|
    PSU [TVS] [H-BRIDGE] [TVS] [MOTOR]
    + ----|-------|--------|------|
  2. Ads Master

    Ads Master

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  3. Alexey

    Alexey Well-Known Member

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    Usually a H-Bridge burns out due to being faulty or being over loaded for too long.
    The Mosfets used in the IMS-2C have internal diodes which would be able to dissipate any power going back through.

    Also Back-EMF does no harm to a motor driver as it is only a counter electromotive force that occurs as the motor is spinning.
  4. xytras

    xytras Member Gold Contributor

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    Hmm I don´t think it was over loaded as it wasn´t even close to be used or warm. It happened when I switched off the PSU in panic because the lever was about to go beyond its limit, on its way to destroy on pot :-/
    Because of that I changed the setup so the motor can turn 360° without causing any physical damage.
    Anyway because of that I assume it was a peak from the switching. Therefore the question if it does make sense to have a TVS between PSU and H-Bridge.
  5. xytras

    xytras Member Gold Contributor

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    sh.. another one burned, even with TVS :( I guess this motor / IMS combination just doesn´t work
  6. Alexey

    Alexey Well-Known Member

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    What is the specification of your motor?
  7. xytras

    xytras Member Gold Contributor

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  8. Alexey

    Alexey Well-Known Member

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    Might I suggest trying the 43A IBT-2 H bridge. Reading the motor characteristics curve and how the motor runs whilst being used in the sim, it is quite possible for the motor to draw over 20A quite easily. I am also expecting the motor to get hot after a short while of use as it has quite a low efficiency rating. It also looks like it is going to be quite slow as the rpm max is around 27.

    Still seems strange that turning off the power causes the motor driver to die. Never had anything like that happen to me before.