Big Pole Changing Motors

I have an application at work running off a large 250kW motor. Occasionally, we would find it convenient to run it a slower speed, say 50% or 75% of maximum speed. We have been looking at electronic or mechanical variable speed drives, but looking at it, it would probably work well using a pole changing motor.
Currently, we use both 4 and 6 pole motors for this application, so a 4/6 pole change over, or a 4/8 pole could work. We would only be running at one speed per product, so the pole changing can be done off line, either via contactors or switches.
Does anyone know a supplier of pole changing motors of this size?
The largest one I've found so far is 20kW from an SEW catalogue.
Other suppliers such as WEG and Demag have drawn blanks as well.

Doug

NHP

Just checked their CD catalog.

No motors, but I rememer a rep talking about their new motor supply contracts a few years ago.

I think I will pick up the phone.

Doug

I'm quite sure that ABB's Electric Machines Group will build the motor you describe.

I don't have their numbers or address outside the US but they have a presence pretty much world-wide.

You should look closely at the economics of a two speed motor vs. going to a VFD. It's true that the VFD itself is very expensive. However, the conversion and installation cost is very low. It's simply wired in to the existing motor instead of the starter.

On the other hand, going to a two speed motor will require the new (and probably expensive) motor, motor installation and alignment, a new (and probably expensive + physically larger) starter and overloads, new control logic, and probably new wiring to the motor.

When you are done, you are stuck with two speeds, neither of which may be optimum. Whith the VFD you will have any speed you want, even faster than nominal if the loads and VFD are sized correctly.

You may want to check out Katt motors in Germany.