N212-D03 TITLE: DIRECT TO PHASE II - Electrical Capacitors for High-Temperature Power Conversion

RT&L FOCUS AREA(S): General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Electronics

OBJECTIVE: Identify and demonstrate that advances in polymeric (or other film materials) dielectrics can be exploited in high temperature (150 °C–200 °C), compact, long life, highly reliable, electrical power capacitors in aircraft.

DESCRIPTION: Electrification of naval aerospace platforms continues. Aircraft designers are being challenged to supply more power to new classes of nonlinear and constant power loads. In response to these new loads, the electrical power generation/distribution system, as well as the electrical loads themselves, are being required to minimize losses, while rejecting heat at high temperatures and maintaining conversion equipment reliability. A well-established design practice indicates component reliability of their insulation systems can be increased by 2 times for every 100 °C the operating temperature is lowered below the design maximum temperature.

While new classes of power semiconductor switching devices based on wide-bandgap materials (i.e., SiC and GaN) are maturing with advertised operating junction temperatures up to 200 °C, the development of high-temperature, reliable capacitors have not followed suit. To achieve reliability, today’s power conversion capacitors are operated at temperatures of ~150 °C – thus limiting converter/inverter fluid-in temperatures at/or below 75 °C.

Capacitors with operating temperatures in the range of -40 °C to 150 °C, with a maximum temperature of 200 °C is the program’s primary goal. There are additional characteristics which are important for aircraft including: operation at altitude (up to 70,000 ft (21,336 m)), weight and volume comparable to state-of-the-art aerospace capacitors, equivalent series resistance (< 2 MO goal), and low inductance (< 50 nH goal). In addition, the capacitors are needed for both DC link applications as well as for AC filters. Capacitors with operating capabilities in the temperatures stated above will enable converter/inverter fluid-in cooling temperatures of 100°C or higher.

The Navy requires representative high-temperature capacitors for aircraft electrical DC link and filter applications with the following characteristics that are important for aircraft including, but not limited to:

• DC Voltage Rating (Nominal): 600 Vdc (Target), 500 Vdc
• Capacitance: 300 uF ± 5.0% (1 kHz – 40 kHz & @ 150°C)
• Operation Temperature: -55°C (Start-up) -40°C – +150°C
• Maximum Storage Temperature: 175°C
• ESR: < 1 MO (1 kHz – 40 kHz at 150°C)
• ESL: < 1 nH per mm of lead spacing
• Dissipation Factor (DF): <= 1.8% @10 kHz; <= 7.5% @40 kHz, 150°C
• Ripple Current: 30 Arms average; 10 Arms @ 80 kHz
• Peak Current: 180 A
• Voltage Ripple: 15 V
• Dielectric Withstanding Voltage: 900 V DC voltage for 30 seconds, no reliability impact with the maximum leakage current < 0.5 mA
• dv/dt > 20 V/µS @ 600 V and 150°C
• Vibration/Shock: Random Vibe = 40 Grms, 10-2000 Hz; Shock = 15 gs@11 ms
• Altitude (Partial Discharge): > 65,000 ft (19,812 m)
• Insulation Resistance: 10 MO between positive terminal or negative terminal and case
• Dimension (Target): <= 8 in3 (20.32 cm³)
• Weight (Target): <= 2.5 lb (1.134 kg)

This SBIR topic seeks development of typical aircraft capacitors and demonstration of reliability and life for these capacitors in representative aircraft electrical power conversion applications. The primary target is 600-800 Vdc capacitors to be used in conversion equipment that operates in 400 Hz power system architectures and with Variable Speed Constant Frequency (VSCF) generator control units. Specifically, this includes the F/A-18 where a need for 35% more electrical power is expected. Better capacitors will help ensure a 100 KVA system can operate without major changes to the F/A-18 cooling system. A secondary target will be for application in 270 Vdc power system architectures (e.g., F-35). A strong collaboration with an electrical generation system or components supplier is highly recommended for Phase II.

PHASE I: For a Direct to Phase II topic, the Government expects that the small business would have accomplished the following in a Phase I-type effort. Have developed a concept for a workable prototype or design to address, at a minimum, the basic requirements of the stated objective above. The below actions would be required in order to satisfy the requirements of Phase I:

The proposal must state a capacitor physical design, the high-temperature material characteristics that will be used, and calculation showing the capacitance can be met in the size and weight constrains.

FEASIBILITY DOCUMENTATION: Offerors interested in participating in Direct to Phase II must include in their response to this topic Phase I feasibility documentation that substantiates the scientific and technical merit and Phase I feasibility described in Phase I above has been met (i.e., the small business must have performed Phase I-type research and development related to the topic, but from non-SBIR funding sources) and describe the potential commercialization applications. The documentation provided must validate that the proposer has completed development of technology as stated in Phase I above. Documentation should include all relevant information including, but not limited to: technical reports, test data, prototype designs/models, and performance goals/results. Work submitted within the feasibility documentation must have been substantially performed by the offeror and/or the principal investigator (PI). Read and follow all of the DON SBIR 21.2 Direct to Phase II Broad Agency Announcement (BAA) Instructions. Phase I proposals will NOT be accepted for this topic.

PHASE II: Develop prototype representative high-temperature capacitors for aircraft electrical DC link and filter applications with the characteristics that are important for aircraft as outlined in the Description.

Develop a test apparatus to demonstrate life and reliability for representative electrical and temperature conditions. Accomplish testing to indicate life and reliability. Deliver test apparatus and test reports. Deliver 25 functional capacitors of each type developed beyond those used in life/reliability testing.

PHASE III DUAL USE APPLICATIONS: Finalize the prototype and perform final testing. Transition in a 100 KVA DC Link Generator Converter Units for use on applicable platforms.

All High-Power Electronic Converters use high-power, high-temperature capacitors to keep size, weight, and cooling requirements low. These characteristics are useful in all commercial converter applications including commercial aircraft, commercial computer centers, and commercial trains.

REFERENCES:

1. Von Kampen, T. "Ensure AC film capacitor reliability with thermal analysis." Power Electronics, March 1, 2001. https://www.powerelectronics.com/content/ensure-ac-film-capacitor-reliability-thermal-analysis#close-olyticsmodal.
2. Bray, K., Wu, R. L., Fries-Carr, S. NS Weimer, J. "AFRL-PR-WP/TP2007-221: Multilayer aluminum oxynitride capacitors for higher energy density wide temperature applications (Pre-Print)." Material Science, January 2007. https://apps.dtic.mil/dtic/tr/fulltext/u2/a466667.pdf.
3. Demcko, R. S. "Evolution of high-temperature capacitors." Proceedings 38th Electronics Components Conference May 1988, pp. 390-395. https://doi.org/10.1109/ECC.1988.12622.
4. Haywood, R. "Downhole tools in the oilfield services industry: Transformation to improve reliability." 2017 IEEE Applied Power Electronics Conference and Exposition, Tampa, FL, United States, March 26-30, 2017. https://www.psma.com/sites/default/files/uploads/tech-forums-capacitor/presentations/is186-downhole-tools-oilfield-services-industry-transformation-improve-reliability.pdf.

KEYWORDS: High Temperature; Aircraft Capacitor; DC-Link; Converter; 100 KVA DC Link Generator Converter Unit