Variator with VFD?

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.

I agree that using the variator to avoid large mechanical issues is probably wise if you can fix the ratio reliably. I would also set the variator ratio so the motor (assuming a 50hz motor) is at 63hz when the machine is at maximum speed. This will provide better performance and also better cooling for the motor at all speeds.

Do not worry about taking that motor overspeed by 13hz. It is good for the motor and should improve the system performance considerably. Only check the gearbox (or variator) input shaft speed for this higher speed. Rarely, lubricant foaming can result and then you cannot use as much overspeed.

In that case, simply reduce the max frequency until the foaming is not a problem and adjust the variator ratio accordingly to get the desired max machine speed.

some comment related with your task,


https://www.quora.com/What-is-the-b...r-asynchronous-motor-and-a-frequency-inverter