Comparison Between Features and Performance Characteristics of Fifteen HP Samarium Cobalt and Ferrite Based Brushless DC Motors Operated by Same Power Conditioner

The impact of samarium-cobalt and ferrite magnet materials on the design and performance characteristics of electronically commutated brushless dc motors of equal horsepower output is presented. This is accomplished through the design, construction and testing of two 15 hp, 120 volt brushless dc motors built for propulsion of electric vehicles, and similar applications. In one of these motors, samarium-cobalt (Sm Co5) is used as permanent magnet material, while in the other the magnets were made of strontium ferrite number 8. The two machines were built to operate from the same power conditioner, which consisted of a transistor chopper in series with a three phase full wave inverter/converter bridge, which consists of six transistor-diode switches. Both of the two motors achieved a continuous 2 hour rating of more than 15 hp with a peak one minute rating of 35 hp. System efficiency (combined motor and conditioner) under rated conditions of 90% was achieved for both machines. Details of these and other performance characteristics and design parameters are presented and analyzed to assess the impact of the choice of, magnet material on design and performance for this, as well as other applications.