Re: [CAD_CAM_EDM_DRO] Re: VFD for series 1 bridgeport

Does anybody have any plans to make a high-power 3-phase inverter? I'm
thinking about charging a couple of BIG juicy capacitors through a
full-wave bridge, and use a sinewave synthesizer (3 of them timed 16666
microseconda apart) to feed a husky set of TRIAC's. I want about 15KVA at
230 VAC 3-phase. Any help would be appreciated.

Best Wishes for safe & Happy Holidays!

RayHex at jnr@...

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> From: Tim Goldstein <timg@...>
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: RE: [CAD_CAM_EDM_DRO] Re: VFD for series 1 bridgeport
> Date: Sunday, December 23, 2001 3:54 PM
>
>
>
> > -----Original Message-----
> >
> > Any recommendations for a good, cheap VFD? I didn't know they
> > convert to single phase. Cool! I do have a rotary phase converter
> > but will be purchasing a VFD soon.
>
> Go to http://www.dealerselectric.com and check out the inverter drives
> (VFD). I have not tie to them other than being a satisfied customer. You
> will need to derate the unit by 50% to use it as a phase converter so for

a

> 2 hp mill you will want a 5 hp VFD. I don't know if they have any left,

but

> the used 7.5 hp Motortronics 230 v units they have listed at $350 are

really

> nice. Got one from them a few weeks ago for $305 plus shipping.
>
> > If I'm understanding you correctly, Tim, the air motor stops and
> > starts on command, and thus the RPM only changes while the shaft of
> > the air motor is turning. So, could I put in a hand crank there and
> > leave the machine at a high RPM setting using the VFD to control
> > RPM? Then, whenever I need additional torque I could crank it down
> > but would still use the VFD to control RPM....????
>
> Yes, if your speed change works anything like the one I have and have

seen

> then the air motor was just an automated way to do what you can with a

hand

> crank. So you can make most of your speed changes from the VFD and only

use

> the built in speed changer to make when you need to radically vary the

RPM

> or if you need to use the back gears.
>
> > Will the VFD brake the spindle motor also?
>
> I have 2 different Motortronic VFDs now. One has built in brake resistors
> and will very rapidly brake the spindle. The other has some breaking

effect

> (20%) and if you want full braking you have to add an optional resistor
> pack.
>
> Tim
> [Denver, CO]
>
> > Addresses:
> > FAQ: http://www.ktmarketing.com/faq.html
> > FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
>
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