WARF: P150363US01

New Rotor Magnet Configuration Delivers Greater Efficiency at a Lower Price


Thomas Lipo, Zhentao Du

The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing a newer and more efficient magnet configuration for electric rotors.
OVERVIEWPermanent magnet machines (PMs) are common in electric and hybrid vehicles, renewable energy and other industrial applications. These utilize permanent magnets made from rare earth materials (such as neodymium and dysprosium) instead of coils as part of synchronous generators. Interior permanent magnet machines (IPMMs) specifically contain these magnets embedded in the rotor for improved performance.

Unfortunately, rare earth magnets are costly and in limited supply. Traditional rectangular designs for IPMM rotors also suffer from pulsating torque, which causes structural vibration, acoustic noise, diminished machine performance and damage to drive components.
THE INVENTIONUW–Madison researchers have developed a streamlined sinusoidal rotor magnet design for interior permanent magnet machines.

By altering the classic rectangular block design for embedded magnet stacks in favor of a sinusoidal, axially varied orientation, researchers have increased the efficiency of rotors in IPMMs in a twofold fashion: Not only does this new design reduce the amount of magnet material necessary for rotor production, but it also provides an optimized distribution of flux that significantly reduces torque pulsation and spatial harmonics. The new design is easy to manufacture and is complementary to rotors already in existence.
  • Hybrid and electric motor vehicles
  • Industrial electromagnetics and automation
  • Minimizes use of permanent magnet material
  • Curtails costs associated with rare earth elements
  • Reduces torque pulsation and subsequent vibration-related damage
  • Simple to manufacture
STAGE OF DEVELOPMENTModeling and simulations demonstrate a significant reduction in torque pulsation as compared to a 2007 Toyota Camry hybrid motor. The inventors are ready to build a prototype for testing and are searching for relevant industrial partners.
For More Information About the Inventors
Related Portfolios
  • Du Z. S. and Lipo T. A. 2015. IEEE Energy Conversion Congress and Exposition. 1773-1780.
  • Zhao W. and Lipo T. A. 2014. IEEE Transactions on Industrial Electronics. 61, 5779-5787
Contact Information
For current licensing status, please contact Emily Bauer at or 608-960-9842.
The WARF Advantage

Since its founding in 1925 as the patenting and licensing organization for the University of Wisconsin-Madison, WARF has been working with business and industry to transform university research into products that benefit society. WARF intellectual property managers and licensing staff members are leaders in the field of university-based technology transfer. They are familiar with the intricacies of patenting, have worked with researchers in relevant disciplines, understand industries and markets, and have negotiated innovative licensing strategies to meet the individual needs of business clients.