Effects of cage-bars for stability of circumferentially magnetized permanent-magnet synchronous generators

This paper describes the effects of cage-bars for the stability of circumferentially magnetized permanent-magnet synchronous generators when the load changes. Two kinds of the generators whose rotors have cage-bars and no cage-bars have been made and used for the measurement of the load characteristics. In addition, a conventional interior permanent-magnet synchronous generator without cage-bars is used for comparison. It has been found that the cage-bars have contributed the stability effectively and that the maximum output power has been increased highly. Besides, the time-stepping finite-element analysis has been used to successfully predict the transient and steady-state performances of the prototype generators.