0
\$\begingroup\$

I'm wondering if I can use an X or Y rated film cap for high frequency DC link filtering/snubbering. The system will be a rectifier+inverter, so the cap in question will go on the DC link between the rectifier and inverter. There will be a big bulk cap (>3mF) to deal with low frequency ripple. The job of the X or Y cap is to do localized filtering for higher frequency noise.

The reason I want to use an X or Y cap in the DC link is that the X & Y caps typically have UL approval while caps listed as DC link specific rarely have UL approval. To achieve UL approval on our product we will likely need UL approval on our DC link caps. Assuming the X or Y cap meets all the voltage and current ripple requirements, is there anything else to consider when using an X or Y cap in the DC link?

\$\endgroup\$
2
  • \$\begingroup\$ are the ripple-current ratings (the self-heating, the temperature rise, the increased aging and the higher failure rates) satisfactory? \$\endgroup\$
    – analogsystemsrf
    Commented Sep 24, 2019 at 14:53
  • \$\begingroup\$ Since this design is not finalized, let's just assume they will be in the final design. \$\endgroup\$
    – user137089
    Commented Sep 24, 2019 at 15:24

2 Answers 2

Reset to default
1
\$\begingroup\$

It depends on what you want the failure mode to be. X caps fail short, while Y caps fail open. Since your snubber resistor will most likely not be rated for continuous operation you most likely would choose a Y cap. Thus, if it fails the HF noise may be present but the snubber resistor will not burn up.

See this article for more information.

\$\endgroup\$
0
\$\begingroup\$

Metallized paper & film or poly capacitor is suitable for high frequency filtering

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.