On 11 Sep 2004 20:18:52 GMT, inch (Peter H.) wrote:



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.

You can likely use the contacts in the existing switch stacks and
retain the use of the levers. While they are not immediately
intuative, its easy to determine which contact is open or closed.

The usual thing that goes wrong with those Hardinge switch stacks is
the roller and spring that detent it into the various positions falls
off when the spring breaks. Easy enough to reform the loop that broke
and reinstall.

Gunner



"At the core of liberalism is the spoiled child -
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosphy of sniveling brats." -- P.J. O'Rourke