Re: [CAD_CAM_EDM_DRO] high frequency spindle motors

Bob Simon wrote:

>>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.
>>
>>
>
>What exactly do the output inductors do? Where do you get chokes that will
>handle the current? Is a 1.5mH line reactor going to satisfy the same needs?
>
>

The PWM scheme these units use assume some minimum inductance for the
motor windings.
If the inductance is too low, very large currents will develop within
the on-time of a transistor,
and will cause the drive to fault. If the motor inductance is too low
(and on these high-speed
motors, it sure is) it will generally saturate the motor core somewhere
during the startup, and
you won't be able to get the motor up to full speed. If you have some
1.5 mH inductors with
suitable current specs, they should work. You'd need 3 of them, unless
they actually have 3
separate inductors in one package. A 3-phase inductor with common iron
for all 3 phases may
not work for this purpose. I got my 1.6 mH inductors from Renco for a
power inverter
project a few years ago, and have some left over.

Jon