RE: [CAD_CAM_EDM_DRO] Re: VFD recommendations for Bridgeport W/gecko 201's (was Boss 3)

Hi Guys,

A VFD is designed to drive a three phase motor and that is all. If you use
it like a single phase to three phase converter you are asking for BIG
trouble.

A VFD outputs volts per hertz waveforms to dive the motor at the commanded
frequency. It is not a sin wave but an approximation of one. A modern VFD
also monitors the current and the voltage of the approximated waveform.

If you put single phase loads on two legs it will go nuts!

Install the VFD to run the motor only and keep the rest of the control
circuit's single phase.

By the way if you reverse plug a VFD running wide open you will blow the
IGBT gates right out of the drive.

Hope this helps.


Best,

Ed Gilbert

Gilbert Engineered Systems
632 Warrenton-Embro Road
Macon, NC 27551
252-257-0539

> -----Original Message-----
> From: Kevin R. Walsh [mailto:krwalsh@...]
> Sent: Friday, March 12, 2004 10:36 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: VFD recommendations for Bridgeport W/gecko
> 201's (was Boss 3)
>
> > "In fact, life can be made easier on the VFD and the motor by
> > soft starting and stopping the VFD and not using the anti-plugging
> > solenoid/contactor."
> >
> > now will that shut the power off entirely to the machine? I'd
> still
> > want to be able to move/control the axis which are going to have
> to
> > have the power on from the VFD. Or am I way off base here? Can the
> > powersupply (rectifier) for the stepper's and the Geckos be
> converted
> > to 220 single phase or 110v?
>
> On this my intention was to take the 220VAC and run the two legs
> through the main on/off switch on the small enclosure. Then through
> the existing fuses. From there the two legs would both go to the
> VFD. Out of the VFD would go to thru the plugging
> contactor/solenoid to the direction switch on the head, to the
> motor. To keep the loads down on the VFD, I planned on using the
> switch just for direction, and turning on and off the VFD from the
> inputs available to it. That way it ramps up/down nicely. Of
> course, you could still bang the switch from full forward to full
> reverse, the plugging contactor should still work, and you just beat
> up the VFD a little more.
>
> If you want to keep everything else 3 phase and run it off the VFD,
> you would just switch the order and run it 220 single phase ->
> Fuses -> VFD -> To the rest of the machine. The full load the the
> VFD then could exceed the 2HP it is rated, but only if you loaded
> the spindle motor pretty hard.
>
> I planned on running the Geckos from a 110V source. You generally
> are not supposed to split the legs of a 220 single phase to
> accomplish this. It has something to do with the breakers not
> working of one is loaded more than the other. I don't quite
> understand this. Anyone know why? At any rate, you could use 220
> or 110 to run a DC supply. I was going to use 110 because I thought
> the transformer would be easier to get. I could be wrong. Either
> way I don't see any way to use any of the transformers in the
> enclosure now. Search ebay for "toroid transformer cnc" and you
> should find one for $60. There are TONS of big capacitors in the
> enclosures to use. And the bridge rectifier should work perfectly
> fine if you get a new transformer. Otherwise a Rectron 1000V PIV
> 35A bridge rectifier can be had from Mouser for less than $4.
>
> Well, that's enough of a novel for now. I can send you a drawing of
> how I intend to wire mine. If you give me maybe 2 weeks, I can send
> you an AutoCAD file of the entire wiring diagram.
>
> Kevin
>
>
>
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