105°C Coolant DC Link Capacitor

Partially funded by US Department of Energy R&D grants, SBE’s significant investment in developing a leading edge film capacitor technology for the critical DC link applications in automotive HEV, PHEV, and EV powertrain inverters has resulted in an array of design tools which can accurately characterize the performance of the capacitor in the application.

Based on 3.7 Million unit hours of life testing (including over 15,000 hours of continuous run time on hundreds of full-size production units, at performance extremes) and on industry peer-reviewed analysis, these simulation tools can now be tied to reliability predictions up to MTTFs exceeding  50,000 hours in the strenuous transportation application environment up to and including 105°C liquid cooling regimes and air cooling topologies.

The SBE life testing methodology and interpretation of results has been reviewed by electric power train customers around the world. In each case, the raw data was presented to quality and engineering specialists followed by discussion of statistical interpretation. Our final presented results have incorporated this peer review and represent more than 70,000 square meters of stressed polypropylene film, which is much larger than typical life test populations. Further details are available for potential customers that are interested in signing a mutual NDA with SBE.

The documents below detail some of our capability and summarize the technical approach and results:

Trise – This document summarizes the approach, analysis methodology, and observed results of temperature rise in a DC link capacitor vs simulation models. The results are applicable to any polypropylene capacitor and scalable to any voltage.

Life Testing – This document describes the SBE life testing program and illustrates how the measured or calculated hotspot temperature relates to service life. The data summary shown below is for 3.8 micron polypropylene film rated at 600V up to 85°C.


Simulation Tools – This document describes how the SBE model was created, validated as well as some of its capabilities for the DC link application.