Performance assessment of ferrite- and neodymiumassisted synchronous reluctance machines

Growing attention towards environmental sustainability of energy conversion and stricter efficiency standards are encouraging the market penetration of high-efficiency electrical motors. Current regulations define international efficiency classes and the testing procedures for direct-on-line machines only, commonly induction motors. Synchronous reluctance machines are a valid alternative to the widely employed induction motors for variable-speed applications, due to their low manufacturing cost and higher efficiency. With proper design, torque ripple can be mitigated as much as to make rotor skewing unnecessary for most of applications. The low power factor downside can be fixed by inserting low-cost ferrite magnet into the rotor barriers, with benefits also on the torque capability and constant power speed range. The aim of this paper is to assess the performance and efficiency potential of one synchronous reluctance and two permanent magnet-assisted synchronous reluctance machine prototypes, obtained by replacing the rotor of a general-purpose induction motor with the said synchronous reluctance ones. The rotor barriers have been designed by means of a genetic optimization algorithm has and then adapted to insert commercially available magnets, compliant with minimum extracost requirements. The two prototypes were comprehensively characterized, to validate the design phase and to investigate the performance of the machines. The provided experimental results are critically examined and commented.