I am building a DC link for an IGBT based inverter.

The input is provided from a 400V 3 phase AC source. I couldn't find capacitor rated greater than 450V in my nearest stores.

I'm thinking of designing a filter with two capacitors in series. I am using 330uF 450V capacitors. The capacitance requirement is less than 165uF. That is, I am OK with halved capacitance.

Is there anything else I need to consider or should I proceed with this design?

  • 4
    \$\begingroup\$ Depending on application, I often use balancing resistors (equal resistors in parallel with equal capacitors) of a few Mohms each; that way the voltage across the caps is roughly equal. Caps of that value might vary by 20% - using even 5% resistors reduces the voltage imbalance. \$\endgroup\$ Jan 22, 2020 at 15:55
  • 1
    \$\begingroup\$ electronics.stackexchange.com/questions/80581/… \$\endgroup\$
    – Phil G
    Jan 22, 2020 at 15:58
  • \$\begingroup\$ What makes you think you are going to see more than 327 volts DC? \$\endgroup\$
    – Andy aka
    Jan 22, 2020 at 16:06
  • \$\begingroup\$ simply because the I am using 400v three phase full bridge rectifier (3 phase full bridge rectifier output is 1.65*Vm) \$\endgroup\$ Jan 22, 2020 at 16:09
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    \$\begingroup\$ You need to consider whether this is "class X" or "class Y"; if one of the caps fails short it will blow up the other one, which may be OK but needs considering. \$\endgroup\$
    – pjc50
    Jan 22, 2020 at 16:38

1 Answer 1


This way, you halves the capacitance, doubles the power rating, internal resistance and lead inductance. As long as your selection of the cap has some reasonable margin, it should be good to go.


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