UQM Technologies Inc. has been granted a US patent (8,928,198, “Brushless PM machine construction enabling low coercivity magnets”) for an electric and hybrid electric vehicle motor design using non-rare earth magnets.
The patent covers the unique magnet geometry and the method of manufacturing the motor.
The majority of electric and hybrid electric vehicles produced today use permanent magnet (PM) motors with rare-earth magnet materials because of the high coercivity of the rare earth materials. Coercivity is a measure of the reverse field needed to drive magnetization to zero after being saturated—i.e., it is a measure of the resistance to demagnetization. The new UQM design enables the use of low coercivity magnets, such as Aluminum Nickel Cobalt (AlNiCo) or Iron Cobalt Tungsten (FeCoW), in PM machines.
UQM says that the new motors will provide a similar level of performance to UQM’s current design, and once the development is completed will allow UQM the flexibility to choose between these systems depending on projected magnet costs into the future.
As outlined in the patent, the new PM machine architecture includes a unique geometrical arrangement that keeps the operating flux of the magnets at a higher flux density than any other known architecture. By operating near the peak flux density of these magnets (e.g., the residual induction), low coercivity becomes acceptable, UQM claims.
Implementation of this patented technology is part of a $4-million Department of Energy (DOE) Advanced Research and Development Grant previously awarded to UQM for the development of non-rare earth magnet electric motors for use in electric and hybrid electric vehicles.
