Re: [CAD_CAM_EDM_DRO] Re: VFD and inverter duty 3phase motors

How much torque will the 1800 rpm motor develop above
60 hz?
Dan
--- doug98105 <DougR@...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, cnc002@a...
> wrote:
> >
> >
> > In a message dated 7/29/2004 10:35:03 PM Eastern
> Daylight Time,
> > JanRwl@A... writes:
> >
> > Should I just get a regular ~3450RPM @60Hz motor,
> and limit my
> VFD to
> > 60Hz, or should I go for an inverter duty motor
> where I can run
> much higher
> > frequencies/speeds. Any comments would be
> appreciated.<<
> > NO! You should get a motor DESIGNED for 400 Hz
> operation, with
> fresh
> > bearings, properly lubricated for that speed. If
> you go [deleted]
> ing with a
> > 60 Hz
> > motor on 400 Hz, even if you DO manage to get the
> voltage right
> for that f,
> > you
> > will PROBABLY injure yourself! When five pounds
> of steel
> (armature)
> > designed
> > for spinning at 3600 RPM is spun at 24,000 RPM
> and the bearings
> seize-up,
> > you
> > are talking major discobobulation! DON'T DO IT!
> See Perske,
> etc. BUY one
> > made for the purpose!
> >
> >
> >
> > I couldn't agree MORE, regular 60Hz motors are NOT
> designed to run
> at high
> > speed. Not only the bearings but the way the
> armatures are
> designed and
> > manufactured are very different. I would think
> the first thing to
> go would
> > probably be the armature and I personally have
> seen a motor
> actually explode when
> > run around 18,000 rpm and that is 6,000 less than
> what you could
> get with
> > certain inverters.
> >
> > DO NOT USE A 60 HZ MOTOR EVEN IF IT IS INVERTER
> RATED. The
> purpose for
> > inverter rating a 60Hz motor isn't so it can run
> at a very high
> speed, but
> > actually so it can run at a much lower speed.
> When you run a
> regular asynchronous
> > AC motor at low speeds it will get hot because
> there isn't enough
> cooling air
> > going over it due to the slow speed of the cooling
> fan attached
> to the
> > shaft. In an inverter rated motor the windings,
> insulation and
> sometimes the fan
> > are different and designed for this situation. In
> some cases
> they may even
> > attach a single phase electric fan to the end of
> the motor for
> cooling at
> > lower speeds.
> >
> > Hope this helps.
> >
> > Randy Abernathy
> > 4626 Old Stilesboro Road NW
> > Acworth, GA 30101-4066
> > Phone / Fax: 770-974-5295
> > Cell: 678-772-4113
> > E-mail: Cnc002@a...
> >
>
>
> Hmmmm......what you guys are saying is contrary to
> the info Baldor
> is giving me. They tell me it's ok to run their
> newer non-inverter
> duty 60 hz rated motors up to 5000 rpm.
>
> With an 1800 rpm 60hz motor that would involve
> programming the max
> hertz output of the VFD to 166 hz.
>
>
>
> Addresses:
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