Re: [CAD_CAM_EDM_DRO] high frequency spindle motors

Bob Simon wrote:

>Some time back someone mentioned using a VFD to drive a high frequency
>spindle motor. I acquired several high frequency spindles but not the drive
>generators.
>
>The spindles have the following specs;
>
>2 pole 3 phase
>1.2 kW at 40000 RPM
>5.5 amps
>167 to 667 Hz.
> >>50 to 200 VAC<<
>
>I understand most VFDs only go to 400 hz., but that would still get me the
>24000 rpm I need. What I don't understand is how the voltage plays a part
>in the motor control. Does the voltage have to be changed for different
>loads or speeds, or is the rating just a usable range?
>
>

Induction motors have what is called a volts/Hz curve, which is very
nearly a straight line.
So, at 167 Hz, you apply 50 V, and at double that, 334 Hz, you apply 100
V. Four times
that is 667 Hz (accounting for a roundoff) and 200 V.

AC tech has a mid-size VFD that goes to 1000 Hz,, that is their MC1000
series. The 1000 Hz
is an extra-cost option. Siemens has the 6SE series of VFD that goes to
650 Hz, apparently
as a stock feature.

With all of these units, you will probably need series inductors on the
3 lines between VFD and
motor. I used 1.6 mH with my Westwind spindle. That would at least be
close for your application.
You will need the programming pad and the full manual to make it work.

Jon