Re: [CAD_CAM_EDM_DRO] Re: 3 Phase drive

riet91@... wrote:

> You can find ML4426 on www.fairchildsemi.com their app note #
> 42004 has shown the high voltage application of this IC. Have you
> seen the HP's HCTL1100 ?

Fairchild bought most of the Micro linear product line (looks like about 300

parts), and has discontinued all but about 25 part numbers!

I checked the app note 42004, but it is really more of the same.
The ML4423 was a great design, producing PWM synthesized
CLOSED-LOOP sine waves for one, two (90 degrees) or 3 phase
motors! It was specifically designed for high voltage induction motors.

The ML4425/4426 is a 12 V disk drive motor driver. They show a
design for up to 240 V, but it feeds the motors square waves!
Yuck! Square waves can be applied to motors operating within
a tightly constrained design window (known load, known speed)
but cause rising losses when the motor is run outside that window,
as the current waveform gets far from the ideal sine waves.

I want to build an inverter for high speed air bearing spindle motors,
that run from 15,000 up to 80,000+ RPM. You really need sine wave
drive to run motors over such a wide speed range.

Jon