As I wrote machine is very old and it is very inconvenient to change motor as it asks for quite a lot mechanical rework. At the end I will do it, if I need, but it is suggested to me from the owners to try different way. Just to mention that motors with more poles tend to have bigger size. My idea is to make speed with variator as close as possible to desired and than use VFD. I would then forbid the change of variator ratio. Anyway, you have helped me with your thoughts a lot. Thank you.