Running 4 hp motor from 1.5kw (2hp) drive. Can work ok.

I have been using a Telemechanique vfd rated at 2 hp on a CVA lathe, 4hp on the motor.

Works very well, use 2 second ramps for speed, up and down.

It would seem that one can use a very underated drive in these situations if not using full capacity of machine or motor.

Comments?

Does this drive have programmable motor overload parameters that are wide enough to protect a motor that is twice what it was designed for?

Stuart

At the ideal volts per hz curve you can get 2 shaft hp from your 2 hp vfd, regardless of the size of the motor. (within limits.)


results are highly depends on the power factor and efficiency of your motor as well: a very well built 4hp motor could be better than 85% efficient and 80% power factor and you might be able get more shaft hp for the same amps from a good 4 hp motor and a 2 hp vfd than an average efficiency 2 hp motor.

starting point for volts per hz something like 70-80% of nameplate for a 2:1 ratio.

you don't really have to worry about overloading the motor because the VFD isn't capable of burning up the motor if its running above about half of its nameplate rpm.. because heat follows amps squared and the vfd simply can't push more than ~60% of nameplate full load amps into a motor twice its nominal size, so the most heat you can push into the motor is on the order of 36% of what it was designed to handle.