Maximizing acceleration capability of magnetically levitated slice motors

Over the last few years industry branches with a growing demand for high purity and contamination-free high-acceleration spin processes, such as biotechnology, chemical, pharmaceutical and semiconductor industry, have tightened their cleanness specifications for the process environments. A recent trend to meet these specifications is to use magnetically levitated slice motors with air gaps being large enough to insert a process chamber wall, which assures the hermetical sealing of the process. The drive design of these motors is challenging due to the employed large air gaps and the demand for maximum acceleration capability. Separate design considerations for a non-saturating stator drive claw geometry and for an appropriate drive winding number have been proposed in the past, not considering the interdependencies of these two designs. This paper presents an overall optimization procedure yielding for minimal acceleration times of magnetically levitated slice motors for different speed ranges and verifies the considerations by measurements on a prototype system.