Re: [CAD_CAM_EDM_DRO] Re: high frequency spindle motors

mayfieldtm wrote:

>I have been looking at the "GS" series VFD's from
>Automation Direct.
>
>http://www2.automationdirect.com/store/Home/Home
>
>(look for "GS Drives" about halfway down the page)
>
>I think these are a little cheaper yet packed with
>extra features such as free software and detachable
>keypad and electronic breaking and such.
>
>

But, I'm pretty sure they won't do 1000 Hz. Maybe 400 Hz, though, which is
more than enough for standard 60 Hz motors.

>Automation Direct claims these units were designed
>with U.S. Power and U.S. Motors in mind allowing
>for simpler circuitry over a more universal drive.
>
>Take a quick look, see what you think of them.
>
>I like the idea of having computer control over
>the unit. The Hitachi units I saw, they wanted
>$180 bucks for the software.
>
>

Most of the units I've seen had 0-10 V and/or 4-20 mA either standard, or
an option, and no software required.

>I have a question about VFD's
>
>Is the full horsepower rating available over the
>full speed range?
>

These drives generally provide constant torque from 0-100% of rated
frequency, and then constant HP above that point. They do this by providing
a straight-line volts/Hz curve up to full voltage, and then constant voltage
above that.

>With my current Belt Drive, if I choose a slower
>belt position, my spindle torque goes up.
>Maintaining approximately same Horsepower.
>Does torque increase with slower VFD speeds?
>
>

No. it can't, because the only way to get more torque is to increase the
current. They can do this for a moment with the torque-boost feature,
but if you do that too long, the windings overheat.

Jon