PCIM Paper Presentation: 20% Increase in Inverter Efficiency Seen with Integrated DC Link Capacitor/Bus

Danfoss - SBE textingSBE Inc. and Danfoss Silicon Power GMBH will present a paper entitled “Integrated DC link capacitor/bus enables a 20% increase in inverter efficiency” at the upcoming PCIM Europe conference, Wednesday, May 21 at 2:00 PM.

Voltage overshoot at switch turn-off traditionally limits the DC operating voltage for inverter systems thus limiting the total power output for a given silicon die.The fundamental first step in overshoot reduction is to minimize the DC link inductance.

The paper provides analysis and testing of different IGBT input configurations and compares “through-hole” and “tabbed” input styles. It then describes how voltage overshoot testing results correlate with previously presented “ring-out” measurements done by SBE.

Finally, it discusses the independent testing of an optimized capacitor/bus prototype topology conducted by Danfoss Silicon Power in their facility in Flensburg, Germany. The combination of the SBE Power Ring Film CapacitorTM integrated with an optimized bus structure can achieve a DC link inductance below 8nH (approaching 5nH), which is less than typical IGBT half-bridge internal branch values. The testing was able to prove by extensive measurements that the new DC link capacitor/bus provided the expected 20% reduction in overshoot compared to standard configurations.

The collaborative project between SBE and Danfoss Silicon Power has helped validate the performance of the technology and the ability to increase installed semiconductor efficiency by operating safely at higher bus voltages. Data extracted by theoretical simulations as well as different measurement methods performed by both parties has proven compatible. Such a design enables to safely increase the DC voltage up to 20%, thus improving inverter performance and volume efficiency with existing IGBT’s; this is a critical starting point for a new generation of higher power density inverters, where more power is extracted from the same IGBTs while maintaining the same total volume and cost. SBE’s US team and Danfoss’s Flensburg engineers worked closely on the design of the DC Link capacitor/bus since it was particularly critical to fit as a replacement in an already existing mechanical frame. Ongoing investigations are being pursued between the two companies since the collaboration has proven to be successful in every aspect. The project has now moved forward to a full scale prototype which is currently being tested at the University of Aalborg.

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