Industrial speed control: are PM couplings an alternative to VFDs?

For industrial applications, the primary consideration of any component or system is reliability. In this aspect, the variable frequency drive (VFD) is now generally regarded as a mature technology of proven track record in a multitude of diverse applications. The adjustable speed coupling system (ASCS), as a newer technology, needs to develop a comparable reputation which, if the mechanical concepts are sound, should be possible as it has a much smaller parts count and is simpler. Maintenance requirements are also small-two bearings requiring periodic lubrication.