Re: [CAD_CAM_EDM_DRO] crank as hell

"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