# AC forklift motor info



## EVDL List (Jul 27, 2007)

> --- Rod Hower <[email protected]> wrote:
> > Jim,
> >
> > Let me know what you find out on these AC motors.
> ...


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## EVDL List (Jul 27, 2007)

>One of the biggest issues that I see is that these
>Danaher motor use an encoder bearing on one end that
>runs 600.00 bucks if it needs replacing 8^o IMO
>that's a pretty costly bearing and in fact costs more
>than most of my total invoices for full DC motor

That encoder bearing is a problem in a lot of places.
I heard one go out on a dynamometer controller one
time. It was a motoring dyno (DC brushed, actually)
and went full-speed when it lost the encoder signal.
The 'crunch' as it took out a rather large diesel
ICE (the engine under test) was impressive. Those
heavy-duty truck engines were not designed to spin
at 6000 RPM!!!

In ICE applications, we also use an encoder on the
crankshaft, but it looks very much like the encoder
on the Siemens AC motors. Fewer teeth, and we use the
motor shaft's own bearings for support. Those things
are really quite reliable. The software is somewhat
tricky to get engine position by time interpolation
but it's not rocket science. ICE controllers have
been doing it since the 1970's. With a 60-tooth
mask, you get plenty of resolution down to maybe
20 RPM. Not quite good enough for servo positioning
but fine for ICE. We go for a timing accuracy of 1/4
crank degree or better. I would think that such
resolution would be fine for EV or forklift motors.

Sounds like there are a lot of idiot designers out
there.... I try not to be one most of the time.

-Dale


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