Hi,
Would I need a special controller? what about the the controller that
comes with the treadmill?
I don't know what the controller inside a treadmill is.
When a motor, of any description, is used as a spindle it comes under stress due to sharp and sudden variations in speed
which are related to cutting and accel/deccel. High accelerations means high currents. Where many controllers fall down
is when the motor overruns and starts generating back into the controller, its a fact of physics and can't be avoided.
The KB controllers I have seen are off-line phase controlled bridges and are pretty robust.
That's not to say that rectifier/DC link/Buck regulator designs cannot do the job, but rather the design needs to be good
to match off-line phase controlled bridges. A well designed and built rectifier/DC link/Buck regulator controller is likely
to be as expensive as a KB unit.
Craig