Automotive

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

• Ability to handle higher ripple currents with less capacitance, weight, and volume
• Potential use of 105°C ICE coolant for power electronics cooling
• Zero capacitor maintenance for the life of the inverter and longer inverter MTBF due to uniform current density, inductance, and dissipation
• Elimination of IGBT overshoot and snubber capacitors
• Most effective isolation of DC storage or supply from AC switching artifacts
• Distributed ‘Crown Terminal’ architecture allowing for operation with uniform current density and simplified assembly
• Smaller inverter packaging
• Overall system cost savings

The main application of the Power Ring Film Capacitor™ in HEV, PHEV, Fuel Cell, and EV systems is for the DC Link Capacitor used in inverters. Typical voltages range from 250V – 1500Vdc and ripple currents range from 40 – 5400 Arms at 10 – 100khz switching frequencies. In earlier applications, Aluminum Electrolytics were used extensively for DC Link capacitors, however, as voltages and ripple currents rise, these may not be the best choice any longer for reliable, size efficient use.

SBE manufactures standard film capacitor sections such as those used in the Toyota HEV systems however the efficiency and cost effectiveness of banks of capacitors made this way are not desirable. Instead, we are introducing the Power Ring Film Capacitor for this application. This product has much lower losses than a conventional array (see graph) and therefore has much less cooling requirement and can provide for significantly greater ripple current filtering in less space, using less weight, and costing less money.

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.

DoE Research Goal of DC Link Film Capacitors using 105°C Coolant
SBE has completed its DoE Phase I SBIR research on the topic of High Temperature, Low Cost Ripple Current Capacitors. The Phase II goal of this research is to produce a DC Link Film Capacitor which can meet the FreedomCAR goals of a 200Arms ripple current, 450V system meeting the required lifetime requirements and requiring only the available 105°C engine coolant.
The following documents present an update on this research:

• SBIR Update (pdf link)
• Status Report and Technology Overview of Leading Edge Development In the field of Increased Power Density Inverter Technology and the use of 105°C Engine Coolant for the DC Link Capacitor (pdf link)

Changing a Common Design Criteria in the Industry
Until now, it has been commonly believed that in order to achieve significant ripple current increases in a DC Link Capacitor bank, a designer needed to greatly increase overall capacitance. This often greatly increased size, weight, and cost.

As you can see, with SBE’s Power Ring Film Capacitor™, this is no longer the case. For the first time, the capacitor has been “designed for increased current” rather than the typical approach of adding more and more capacitors until the current rating is achieved. The system results can be remarkable. Please contact us for more information on how to best take advantage of these design characteristics.

Integrating the DC Link Capacitor into the Inverter Design or the Motor itself
To most optimize the power of the shape™ that is provided by the annular form factor capacitor, the DC Link/Inverter/Motor connection needs to be re-thought and has been by a number of customers. These paradigm-shift designs are by no means required to obtain great advantages from the Power Ring Film Capacitor but if implemented can produce “game changing” results for the innovative designer.

Patent Pending designs for the use of IGBTs integrated with the SBE Power Ring for increased Power Density Inverters are presented in this paper: Improve Your Inverter Performance with SBE’s Innovative Power Ring Capacitor Design (pdf link).

Check out all of the possible layouts which take advantage of the annular form factor shape for ripple current filtering.

Circular components situated around the drive shaft are the most efficient use of space for an electric motor application. Additionally, the “coaxial” nature of the current flow, which occurs when situated this way, increases efficiency of the system and minimizes EMI (Electro Magnetic Interference) through the circular and counter flowing current paths. Check out our system-level concept animation.
Check out the impressive specifications of this DC Link Capacitor (pdf link) which was designed for the motor shaft to go right down the center of the hole.

Obtaining greatly increased performance using a conventional system footprint
Many customers use the Power Ring Film Capacitor as a drop in replacement for a bank of Aluminum Electrolytic or conventional Film Capacitors.

Here are some of the electric transportation applications where it is used:

• Powertrain Inverter DC Link Capacitor
• Powertrain Inverter Snubber Capacitor
• Powertrain Inverter EMI Capacitor
• Electrification Inverter Capacitors for Truck Applications
• Military Hybridization
• Storage Container Electrification

And here are some actual examples:

• A 300µF DC Link Capacitor in a 150Arms, 450Vdc system requiring less than 120mm in diameter and replacing 3 Aluminum Electrolytic cans.
  Check out specification details (pdf link).
• A 675µF DC Link Capacitor allowing successful implementation of a 200Arms, 450Vdc system in a space proven too tight for a conventional film capacitor array.
  Check out specification details (pdf link).

Contact our application engineering team to discuss your requirements.