A newly developed ripple-free precision toroidal type motor

Demands for ripple-free spindle rotation have recently increased in a variety of industrial sectors, i.e., electron beam mastering systems, semiconductor production instruments, etc. However, typical electric motors usually have torque ripple caused by the cogging force and uneven magnetic flux density, which deteriorates the spindle performance. This paper presents a newly developed torque ripple-free precision toroidal type motor. The magnet yoke of the developed motor is designed so as to provide an ideal sinusoidal magnetic flux distribution which can generate smooth torque. Evaluation results confirmed that the developed motor achieves superior performance.