AC Filter Capacitors

AC filter capacitor bank

480VAC, 1250µF per phase

Catastrophic failure of conventional AC filter capacitors is a major problem for network power, alternative energy, and UPS applications. SBE has developed a next generation dry-film AC Filter Capacitor that combines the advantages of the Power Ring annular form factor with patented segmentation technology. Utilizing the same core attributes and tools that made the transportation applications successful, the SBE Power Ring Film Capacitor™ is now being designed into the next generation systems in the solar, wind, utility scale power conversion and other specialty power system markets with the same system benefits. SBE’s integrated solution eliminates unreliable conventional capacitors with pressure interrupters that often fail catastrophically with significant collateral damage.

Enabled by the annular form factor Power Ring Film Capacitor™  and SBE patented segmentation technology, the AC Filter Capacitor allows you to:

  • Immediately reduce AC capacitor associated component and labor costs
  • Increase life
  • Decrease maintenance costs
  • Increase reliability
  • Dry film technology
  • Eliminate failures which cause collateral damage
  • Simplify supply chain

AC filter capacitor reliability is acknowledged as a problem across the power conversion industry and system vendors have been forced to address the issue. The question remains as to what can be done at the fundamental capacitor design level to provide acceptable reliability without the need for de-rating.

SBE’s AC filter capacitor (pdf) has been developed to address this very issue. The key targets for this design are defined as follows:

  1.   Eliminate catastrophic failure (benign failure mode)
  2.   No need for internal fuse or pressure interrupter
  3.   Runs up to 20°C cooler than conventional cans and dramatically reduces cooling requirement
  4.   Oil-free
  5.   Explosion proof design and packaging

There are a number of features of the SBE Power Ring capacitor which prevent the type of failures which are seen in typical film capacitors for this application. SBE’s patented end connection and segmentation technology allow for safe management of high stress and prevent “unzipping” failures which are often the beginning of catastrophic failure. In addition, SBE’s Power Ring capacitors are not sealed in a can, therefore overpressure cannot occur. Finally, the large surface area and short thermal path to the end faces of the Power Ring are ideal for reducing temperature rise, therefore extending life or increasing cooling flexibility.

Instead of managing a supply chain of several individual components (capacitors, bus structures, housing, terminals, etc…), SBE’s Power Ring Film Capacitor™ AC solution (pdf) ships as a fully integrated unit. This integrated unit enables simple installation, in the factory as well as in the field. Upgrading existing filter capacitor banks is very straightforward and simple.

The SBE engineering team can help you optimize a bank design which can drop in to your existing space or allow you to create a leading edge, new design. A drop-in solution facilitates a simple path for field testing and system evaluation. This also allows for convenient implementation of second sourcing since the AC capacitor bank is not changed dimensionally – but cost and performance are improved.

SBE is engaging designs in the industry globally. We are ready to introduce your team to the great benefits that others in the industry are implementing in their next generation systems. Please feel free to contact us to set up a call or to discuss your system requirement.

SBE has reports available to qualified customers.
Please inquire at [email protected]

  •   ACCELERATED testing in attempt to initiate hard failures at 100°C and 30% overvoltage (results show that one test unit failed beningly with no collateral/catastrophic damage)
  •   CAPACITANCE REDUCTION LIFETIME PREDICTION TESTS (results show 80,000 hours with 10% to 15% capacitance reduction)
  •   DISSIPATION FACTOR TRENDING (results show less than half of conventional cans demonstrated long term stability)
AC filter 3 phase

End-to-end 3 phase unit

AC filter capacitor bank

Vertical stack 3 phase unit

Side-to-side 3 phase unit

Side-to-side 3 phase unit







A 3 phase system can easily be realized using the single phase unit as a building block. An example system is shown. Other orientations available.