LOW-COST LIGHTWEIGHT HIGH TORQUE MOTORS FOR APPLICATIONS OVER A WIDE TEMPERATURE RANGE

IRON-BASED RARE EARTH-BORON PERMANENT MAGNETS OF THE COMPOSITION FE14ND2B WHICH WERE DISCOVERED SEVERAL YEARS AGO POSSESS MAGNETIC ENERGY PRODUCTS EXCEEDING 40 MGOE. THE OPPORTUNITY EXISTS TO DESIGN ASYNCHRONOUS MOTOR WITH SUCH PERMANENT MAGNET MATERIALS. SINCE THE WEIGHT OF A MOTOR IS INVERSELY PROPORTIONAL TO THE ENERGY PRODUCT OF THE MAGNET, IT IS CLEAR THAT MOTORS DESIGNED FROM SUCH HIGH ENERGY PERMANENT MAGNETS ARE EXPECTED TO BE SMALLER IN SIZE AND TO POSSESS HIGH TORQUE. SUCH MOTORS ARE USEFUL FOR SEVERAL SPACE APPLICATIONS, SUCH AS IN OPERATING BEAM CONTROL EQUIPMENT, TRACKING AND POINTING WEAPONS, POSITIONING MIRRORS AND POWER GENERATION. THE MOST POPULAR OF THESE PERMANENT MAGNETS MADE OF IRON-NEODYMIUM-BORON RECENTLY HAS BEEN SHOWN TO BE LESS USEFUL FOR SPACE APPLICATIONS DUE TO ITS SUSCEPTIBILITY TO RADIATION DAMAGE AS WELL AS ITS ANOMALOUS BEHAVIOR AT LOW TEMPERATURES. THE POTENTIAL IS BEING EXAMINED OF IRON-COBALT-PRASEODYMIUM-BORON MAGNETS FOR MOTOR DESIGN. THIS MATERIAL POSSESS MAGNETIC PROPERTIES SUPERIOR TO IRON-NEODYMIUM-BORON ALLOYS IN THAT IT DOES NOT EXHIBIT ANY ANOMALY AT LOW TEMPERATURES. THESE MAGNETS ARE BEING FABRICATED WITH THEIR SURFACE PASSIVATED WITH A LAYER OF BORON NITRIDE TO REDUCE POTENTIAL CHEMICAL CORROSION AND INCREASE WEAR LIFE. A COMPACT, HIGH TORQUE MOTOR WITH SUCH A MAGNET IS BEING DESIGNED.