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HV Snubber circuit

  1. Jul 11, 2008 #1
    Hello All,

    I'm designing a high voltage snubber circuit to protect a MOSFET which is driving an inductive load to produce BEMF spikes. I am expecting that the snubber capacitor will have to handle 500-1000V transients with greater than 10000V/ms rise and fall times, which I hear can burn up most caps. So I began looking for some good RF capacitors (around 5-10 nF) that could handle the load and someone recommended to me that I look at using Silver Mica capacitors. But seeing how expensive they are, I am wondering if there are any alternative types of capacitors that have similar specs. I would just go for ceramic caps, but I hear they are not good for this either?

    Jason O
  2. jcsd
  3. Jul 11, 2008 #2


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    You hear right about most capacitor types failing in this type of installation.
    I think the ones we used were Polypropylene film or Polystyrene film capacitors.
  4. Jul 17, 2008 #3
    Can you catch most of the BEMF using a flyback diode across the load?
    Otherwise you want to look at polypropylene film construction.
    What is the total capacitance you require?
    The 10kV/ms rise time is generally easy to meet, as most snubber capacitors are rated at >1000V/us at that voltage.
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