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  1. #1
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    Will this ceramic capacitor be damaged by overvoltage spikes?

    Hi,
    I exposed a 630V rated ceramic capacitor (1812, X7R) to a spike voltage of 680Vpk. (the spike voltage as in the attached)
    It did not blow up. In spite of the fact that I exposed it to this spike repeatedly, every 4 seconds, over a 20 minute period. Do you think I have damaged this capacitor in any way?
    How long would it be before this capacitor did get damaged, when treated like this?

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    Re: Will this ceramic capacitor be damaged by overvoltage spikes?

    I think some manufacturers print reliable ratings and other manufacturers concentrate on making low cost junk.


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    Re: Will this ceramic capacitor be damaged by overvoltage spikes?

    I exposed a 630V rated ceramic capacitor (1812, X7R) to a spike voltage of 680Vpk
    Even peak voltage ratings have limits: it is never specified but may be +/-5%

    Exact nature of the damage is usually not specified. Some damages are cumulative but some may recover too with time.

    I do not know whether capacitors are individually tested during manufacture; even running them at the max rated current can decrease the life expectancy.

    Sudden failure of a component is a Poisson process; you can predict failure only in a statistical sense.

    Roughly speaking, the mean life expectancy will be reduced due to the overvoltage in an exponential fashion.

    As your actual overvoltage is small, the reduction in life expectancy will perhaps be small.

    However, the usable life of an assembled product will be limited by the shorted lived component.


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    Re: Will this ceramic capacitor be damaged by overvoltage spikes?

    MLCC are good for quite a bit of over-volts - the acid test is the leakage current at rated volts - when this starts going up - you have damaged it ...


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    Re: Will this ceramic capacitor be damaged by overvoltage spikes?

    Thanks,
    I must admit, I once worked in a huge multinational aerospace company. I was doing a board where I needed more capacitance but didn’t have room. We weren’t allowed electrolytics, had to be ceramics. I was publicly trashed in front of the whole office by the Chief Engineer who told me that I should have used ceramic capacitors which were only rated for about half the rail voltage (because they were smaller and I would fit more of them on) …because as he said, ceramic MLCC capacitors can easily withstand this, and he said it was a mark of my ignorance that I was not aware of this.



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    Re: Will this ceramic capacitor be damaged by overvoltage spikes?

    Hi,

    What value is the capacitor.

    Why this question?
    I see high rise and fall rate. With a capacitor this means high charge and discharge current. I wonder if the shown waveform and voltages are valid. Are you sure the waveform really is measured directly at the capacitor connections.

    Klaus



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    Re: Will this ceramic capacitor be damaged by overvoltage spikes?

    hello Treez, that engineer was a bit ill informed himself - even X7R MLCC's have a characteristic of falling effective capacitance with DC bias voltage - at 1.5 x Vrated the cap will be about 35% of rated ...

    - - - Updated - - -

    also - in aerospace - I am surprised there was any tolerance for exceeding any data sheet rating ... - there would not be today ...


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