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TIDA-01606: How to calculate the split electrolytic DC-link capacitors used for making neutral point and why the film capacitors are used?

Younes Mohammed Tsabet
Intellectual 400 points
Part Number: TIDA-01606

Hello all,

I was looking into the 10-kW, Bidirectional Three-Phase Three-Level (T-type) Inverter by TI. I wondered how they calculated the capacitance of these bulk electrolytic capacitors used to split the dc-link. i know the 600V is half the dc-link voltage plus some margin but 120uF !? and why they used 4 in parallel? is it because of the ratted ripple current?

and also why are these film capacitors used here (in red circle)? and how to calculate its value.

here is the link to the schematic.

Thank you,

  • 0
    TI__Intellectual 2800 points

    Hi Mohamed,

    in a T-Type converter you need to have two kind of capacitors: electrolitytic caps and film caps

    Electrolytic caps are used for the power ripple coming out from this 3 level topology.

    Film caps are used for handling the current ripple coming out a the switching frequency.

    In general, I suggest you to run simulation https://www.ti.com/tool/TIDA-01606#tech-docs which can be found in the following link.

    4 caps are placed in parallel because when you working with reactive load the power ripple is high, thus leading to high ripple current in the caps.

    Thanks

    Best Regards

    Riccardo