Re: [CAD_CAM_EDM_DRO] crank as hell

Sven: How about using an automotive starter motor with a bendix still attached. The bendix would allow the motor a couple of turns
before actually starting to turn your centrifuge. Just something to consider. Carey

Jon Elson wrote:

> "Sven Peter, TAD S.A." wrote:
>
> > Hello folks,
> > a off topic question.
> > For a actually working centrifuge (High frequency induction for metal
> > casting)
> > I shall put a new motor on that starts up much faster.
> > The 7 kg cross beam of 73 cm length needs with the original 250 watt
> > (1/3 hp)
> > normal single phase motor two turns to come on speed.
> > Result: The castings come out defective.
> > First I thought about to put a 1 or 2 hp three fase motor on it.
> > Are there other motor types that still have a better cranking at the
> > start up???
> >
> > Sorry, but 95 percent of my daily bread experience is based on three
> > fase motors.
>
> 3 phase motors running from high-capacity mains can accelerate very
> quickly. Using a rotary converter or other means of supplying 3 phase
> from a single phase supply will make the motor start slower. A big
> DC motor started by connecting it to a DC supply with a big capacitor
> bank can start as fast as you could possibly need, including spinning
> the armature on the shaft. You can get starting torque that will break
> almost anything. Reducing the mass and rotational inertia will help it
> to spin up faster. It may be advantageous to use a gearbox with a
> modest reduction ratio, rather than trying to make a 1725 RPM motor
> start the centrifuge up to 600 RPM or so. It would also be safer if
> the power was ever left on too long. I sure wouldn't want a stuck
> relay or switch to cause a mold full of molten metal to fly across the
> room.
>
> Jon
>
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