DC Link Capacitor Sizing

ali_

Hi,

I want use CRD07500AA12N-FMC with induction motor.

In the PRD-07561 user guide there are two equations for DC Link capacitor sizing (Page20).

ΔV and ΔI equations have not taken account the power or DC BUS current. How can I estimate the 

DC link capacitance according to different power levels? Also Capacitor RMS ripple current has a big role on the inverter operation life. 

How can I calculate the capacitor RMS ripple current with switching frequency, load current etc variables?

Best regards,

Forum_Moderator

Thank you for your post, it has been approved and we will respond as soon as possible.

JHayes

Hi ali_,

Beyond the simplified equations presented in the user guide, the following paper is a great resource to calculate the RMS current stress that the DC link capacitor will see based on the load current, power factor, and modulation index of the operating point depending on your load. This will be the primary criterion to size your DC link capacitor, whereas the actual capacitance value should be determined by the acceptable voltage ripple and required ride-through energy storage.

J. W. Kolar, T. M. Wolbank and M. Schrodl, "Analytical calculation of the RMS current stress on the DC link capacitor of voltage DC link PWM converter systems," 1999. Ninth International Conference on Electrical Machines and Drives (Conf. Publ. No. 468), Canterbury, UK, 1999, pp. 81-89, doi: 10.1049/cp:19990995.

Thanks,

Jonathan

TBhatia

Hi, I hope that this answered your question. I will close this discussion for now but if you have a follow up question, please "Start a New Discussion" and we would be glad to support you further.