Transportation


Design your inverter with higher power density,
lower cost and increased reliability.

Power Ring Film Capacitors™ bring the following advantages and allow our engineering team to develop with you leading-edge solutions for your inverters:

AT100027

  • Ability to handle higher ripple currents with less capacitance, weight, volume and cost
  • Lowest hotspot temperature rise in the industry providing longest life
  • Minimum IGBT voltage overshoot and increased silicon utilization – ESL 5 – 15 nH
  • Smallest volume and profile facilitating inverter integration and power density

The main application of the Power Ring film capacitor in HEV, PHEV, fuel cell, and battery EV systems is for the DC link capacitor used in inverters. Typical voltages range from 250V – 1500Vdc and ripple currents range from 40 – 500 Arms at 5 – 20kHz switching frequencies.

The Power Ring film capacitor allows for a much reduced capacitor volume and cost for a design’s given ripple current requirement.

  • SBE has the simulation and design tools to help you safely predict the right DC link capacitor size for your requirement with confidence.
  • SBE has the life data and “in field” experience to provide the needed component reliability guidance to your team.
  • With SBE technology and experience, you can design your system for minimum DC link capacitance without concern about the amount needed for reliable life.

Integration of your Power Electronics Module

Use of 105°C ICE coolant for power electronics cooling is a solution that reduces space, weight, and costs by over 50%. SBE has demonstrated such results and is partnering with leading companies in silicon, bus, and cooling for a world class solutions to your demanding requirements. Read more in our technology section Integrated Modules.

SBE’s Power Block™ addresses the demanding transportation requirements of high power density but low cost powertrain inverters which employ either conventional Silicon or Silicon Carbide switches and are scalable across numerous platforms of power need. The Power Block combines the proven Power Ring Film Capacitor™ attributes of industry leading ESL/ESR and Amps per micro-Farad with its vertically integrated, surface mount, capacitor/bus assembly to maximize power density. The Power Block features the cost saving, size reducing and performance increasing attribute of direct, shared cooling of the bus and IGBT. The Power Block power density allows for smaller inverters while its extremely low ESL allows designers to increase operating voltages without fear of overshoot damaging the IGBT. The designer is given the ultimate in power density and system scalability.

Use of elevated coolant temperatures for power electronics in high density applications

The Power Ring film capacitor has much lower losses than a conventional DC link solution, often comprised of an array of film capacitor windings in a box or a group simply-connected off-the-shelf packaged capacitors. SBE Power Ring thus has a reduced cooling requirement for a given current demand and can provide for significantly greater ripple current filtering in less space, using less weight, and costing less money.
graph temperature rise power ring vs conventional capacitor
The above graph shows a representative example of a typical DC link capacitor approach vs. SBE Power Ring using the same amount of capacitance and identical film.

Until now, it has been commonly believed that a designer needed to greatly increase overall capacitance in order to achieve significant ripple current increases in a DC link capacitor bank. Often it greatly increased size, weight, and cost.

With SBE’s Power Ring film capacitor, for the first time, the capacitor has been “designed for increased current” rather than adding more and more capacitors until the current rating is achieved. The system results can be remarkable. The representation below shows the industry commonly-accepted trade between capacitance volume and current handling capability for film vs. aluminum electrolytics. Also shown is the SBE Power Ring technology ability to “tilt the curve” for leading edge designs.

capacitance ripple current graph capacitor

Design Optimization using the SBE Power Ring film capacitor

What are the implications of lower temperature rise, lower ESL, and lower ESR on the design and performance of the inverter?
With SBE Power Ring, it is critical to identify the key constraints on the project to ensure key goals are achieved, system timelines are held, and the right tools and products are utilized – right at the start of the design process. Typically, inverter projects fall into three categories:

  1. Drop in Replacement – The design specification is complete, however, there is an opportunity to replace the traditional capacitors with SBE Power Ring by leveraging the same space but achieving significantly increased performance at no additional cost. This allows current engineering effort to be leveraged upward as customers look to scale designs across different platforms. SBE has significant experience is successfully achieving this outcome with transportation customers.
  2. Modification to an Existing Design – The volumetric size and dimensions of the inverter housing design specification are complete, however, there is an opportunity to change the internal layout and connections of the active and passive components (the power electronics module). In this case, we suggest an initial dialog with the experienced SBE applications engineering groups (located locally on 3 continents – Europe, Asia, and North America). We have great experience in optimizing your “design envelope”, often in partnership with experience from our silicon, interconnect, and cooling partners. The outcome is a “new level” of performance yet still meeting your cost and size goals.
  3. Complete New Design – The design specification has not been defined and there is an opportunity to explore new options without the constraints of an existing envelope. Examples of these are inverters integrated in motor housings, new and challenging power density requirements, combination of auxiliary and powertrain systems, and completely new cooling and/or airflow topologies, and connections of the active and passive components (the power electronics module). In this case, we suggest an initial dialog with the experienced SBE applications engineering groups (located locally on 3 continents – Europe, Asia, and North America). We have great experience in optimizing your “design envelope”, often in partnership with experience from our silicon, interconnect, and cooling partners. The outcome is a “new level” of system performance yet still meeting your cost and size goals.

The choice of SBE Power Ring technology in any of these three situations will yield improved performance, however, the more flexibility in the design parameters, the better opportunity exists for a breakthrough in W/cm3, cost, reliability, and size. The ability to achieve high density design goals for inverters is directly impacted by the constraints on the development cycle.

SBE has extensive design tools and life test data to support all of our design recommendations as well as an ever increasing amount of successful field experience in industry.

Contact our application engineering team to discuss your requirements.

Additional Readings:

  1. Our technical team has presented numerous technical papers/presentations on the subject of using the Power Ring film capacitor in the DC link application including optimum ways of connecting the capacitor to the switch bus.
  2. DoE Research of DC Link Film Capacitors using 105°C Coolant
    SBE Inc. has been the recipient of a Phase I and Phase II grant from the Department of Energy (DoE) and has final life test data on the use of the SBE Power Ring technology in elevated and 105°C coolant conditions.
  3. Examples of pilot run and low rate production fielded applications include:
    • Passenger EV and PHEV Powertrains
    • Delivery and Fleet Utility Truck Powertrains
    • Large and Small Passenger Bus HEV and EV Powertrains
    • Mining Vehicle Powertrains
    • Utility Truck and Passenger Bus Auxilliary Power Units
    • Off Road Vehicle Powertrains including Watercraft