The motor is a Diehl 220 V., 3 phase, two speed motor. The spec plate
lists the current draw as:

1720 RPM 3/4 HP 2.3A

875 RPM 3/8 HP 3.2A

What is causing the to motor to suck up an (almost) additional Amp at
the slower speed? I can understand that multi speeds would require some
design compromises, but that seems like a lot of inefficiency.


The motor is a one winding, "consequent pole" motor, in which its six total
wires are operated either: 1) three connected to the source and three
open-circuited, or 2) three connected to the source and three short-circuited.

It is a contant torque motor.

Permanently connect the motor in high speed mode and then permanently connect
the VFD to the remaining three motor leads.

You will have to bypass the motor starter as there should be no contacts
between the VFD and the motor.

Simulate the functions of the HI/LO lever and FWD/REV lever using microswitches
which are input to the VFD.