DHi's Hipercon Brand Metal Fiber Brush Technology

The story behind Metal Fiber Brushes (MFBs)

HiPerCon metal fiber brushes (MFBs) possess unique performance characteristics giving them clear and demonstrated advantages over traditional carbon brushes commonly used throughout the world in an almost endless variety of motor applications.

Our modern MFBs were developed through extensive R&D efforts funded under the Federal government’s Small Business Innovative Research (SBIR) program. This highly successful cooperative endeavor brought together HiPerCon, Defense Holdings, Inc. (DHi), the Naval Sea Systems Command (NAVSEA), and the University of Virginia. The result: an entirely new kind of brush that helps reduce motor wear and tear while minimizing costly maintenance and downtime issues.

HiPerCon’s MFBs have proved highly successful in homopolar motor applications where extremely high current capacity is required. This and other MFB advantages promise to make these technologies increasingly important in developing extremely power dense motor and generator applications.

Slip ring MFBs developed by HiPerCon and DHi are currently being installed in the submarine force 500kW Ship Service Motor Generators under SHIPALT’s 4415KP (SSN 21 class), 4429KP (SSN 688 class), and alteration SSBN TZ 0906KP (Trident). Key performance attributes of slip ring metal fiber brushes include the following:

• Current densities of up to 250amps/sq inch are easily obtained.
• Current densities of up to 1000amps/sq-inch have been obtained under select conditions.
• Non-dimensional wear rates of 2 × 10^-11 at sliding speeds of 20 meters/second in open atmosphere.
• Extremely high tolerance to atmosphere contaminants.
• Extremely low electrical noise across the brush slip ring interface.
• Lower levels of acoustical noise.
• Less than 1/5 the wear debris volume of carbon brushes.
• Improved machinery efficiency due to a very low and stable voltage drop and lower frictional forces.

While the successful operation of MFBs in submarine applications proves their viability in a shipboard environment, these applications scarcely begin to utilize their full performance capabilities. So it’s not surprising that our MFB technologies have now expanded to include aviation applications for the U. S. Navy and Air Force.

The Latest Developments:

Recently, several important developments—including the installation of a new ownership and management structure at HiPerCon that actively promotes and welcomes teaming arrangements—have prompted a renewed interest in the company’s exciting and promising MFB technologies. HiPerCon’s new management is open to all forms of teaming agreements, including licensing MFB technologies to OEMs for specific applications.

HiPerCon’s ownership has also tasked its new management team to aggressively pursue the development of slip ring metal fiber brushes. Core scientific knowledge in the MFB arena has been retained by the HiPerCon team which seeks to expand the knowledge base of MFB technologies.

Indeed, other key technical developments have allowed the HiPerCon team to broaden the range of applications that can be addressed by MFB technologies. Significant technological advances occurring in recent years include:

• New techniques for brush manufacturing that promote far superior shape conformance and retention. These techniques have proved instrumental for consistently manufacturing brushes to tight physical tolerances and ensuring that they retain their shape in severe mechanical, electrical, and magnetic environments. This allows us to manufacture a wide size range of brushes from 1cm to 10 cm widths.
  
• Other improvements in MFB design and construction that address the need to minimize brush circulating currents resulting from non-aligned magnetic fields. High internal cross resistance development for commutating motor-generator applications can be utilized to eliminate concerns about applying metal fiber brushes in high magnetic fields. This is particularly important for MFBs in homopolar machines and in other high strength and non-aligned magnetic fields.
• New developments in brush lubrication strategies that extend brush and slip ring service life in severe environments where they are exposed to volatile contaminates and low humidity.
  
• Advancements in oxidation suppression additives. These allow metal fiber brush use on various slip ring materials including copper and copper alloys without slip ring plating or the use of a cover gas.
• Improved understanding and development of processes and strategies to mitigate the impact of brush current polarity on brush and slip ring service life.
  
• Significantly increased understanding on optimizing the complete brush system design to fully utilize the brush performance capabilities. The HiPerCon team has vastly upgraded its CAD modeling capabilities, allowing us to team with OEMs to design brush systems that optimize MFB performance characteristics.
• Improved, quality-driven manufacturing processes providing first time quality to exacting standards. DHi has instituted a rigorous ISO-9000-2001 certified quality system.

HiPerCon’s MFBs have been used in homopolar motor applications where extremely high current capacity is required. We believe that with recent improvements, MFBs can operate stably mechanically, electrically, and thermally in such machines while offering acceptable electrical and frictional losses and wear rates. MFB technologies are also applicable for transmitting current between rotating and stationary elements of rail gun and coil gun launchers.

There is little question that HiPerCon’s metal fiber brushes are fully capable of satisfying the extreme performance requirements of tomorrow’s power-dense motor and generator current collectors. Significant technical advancements made by the HiPerCon team over the past few years only reinforce their proven ability to satisfy such requirements. As a result, HiPerCon’s new management team is eager to conduct open discussions and provide OEMs with solutions addressing the need for high capacity current collectors.