Installation of an AC Drive on a Plastic Extruder
Changing the pulley ratio will reduce the output torque by 30 percent. Since the motor runs lightly loaded at maximum speed, that will probably not cause a problem. The torque required to drive an extruder should be essentially the same at 143 percent of the current speed as it is at the current speed.

Starting torque could present a problem. The torque required to start the extruder may be higher than the normal operating torque. The torque due to inertia should not be significant. Higher torque may be required to overcome static friction and get the drive train and extruder moving from standstill. If a significant portion of the heating of the material in the extruder comes from the mechanical friction and compression, high torque may be required for a cold start.

With a "low overload" VFD, no more than rated motor torque will be available for starting. A "high overload" VFD could provide 150% of rated torque or perhaps a little more. To get even 100% torque for starting, a "sensorless vector" VFD is likely required. The V/f control schemes are not likely to be sufficient. If "FCC" is a sensorless vector method, that should provide 100% torque at rated current for starting. Look carefully at the manufacturer's description of starting torque performance.

We are discouraged from answering questions about what to purchase. In general, it is a good idea to consider manufacturers with good reputations that sell globally. However it is also beneficial to consider local suppliers that have brands that have good local reputations. A local supplier that can give good advice can be very valuable. There are many VFD brands that have good reputations. There are models that are intended to drive fans and centrifugal pumps. Those models are unsuitable for constant-torque loads like extruders.