Re: [CAD_CAM_EDM_DRO] Re: Monarch conversion to VFD

>
> Hi Paul:
> I heard about the genuine Monarch replacement; the reports on prices
> scared me off that notion!!!
> I'm told to expect about the same money again to do the conversion by this
> route. OUCH!!!
> An AC motor and VFD can't possibly cost 10 grand. Can it???
> At 650 bucks a day charge out rate, I can afford to spend a couple of weeks
> on it and still come out ahead, but I don't want to.

Yeah, I didn't say they were cheap. I heard they sell rebuilt 10ees for
around 65K US.

> Problem is, any Monarch that I buy has the same potential problem, which is
> a major Achilles heel on an otherwise almost perfect machine for my needs.
> The solid state DC controller that you mention is the route the machinery
> dealership has been struggling with for the last 4 months.
> So far--- no bananas!!

> With my nonexistent electronics expertise, I'm looking for a solution that
> involves only a simple hookup.
> Jon Elson posted with the comments that it's not a big problem so I'm
> hopeful, but then he's a whiz at this kind of stuff.
> Thanks very much for your comments; I appreciate it!!
> Cheers

This really isn't that bad a problem. For the DC solution, talk to the
tech folks at KB Electronics (www.kbelectronics.com); they've had a
number of people do the DC conversion. I'm missing the original message,
but it sounded like they couldn't get the top speed? They've probably
don't know about field weakening on DC motors then.

Control on the 10ee motor is handled in 2 stages. From bottom to
some intermediate stage, the field voltage is constant and armature
voltage is increased. Above that point, armature voltage is held
constant and field voltage is _decreased_. If you don't do both
right you won't get the full range on the motor speed. And if you
don't have a safety cutout on the field supply, if it goes out
you can have a very dangerous overspeed condition happen.

The VFD conversion is electrically simpler (as Jon said, a couple of
switches and a potentiometer and you're good to go), but some
fabrication is necessary. More expensive if you buy everything new,
but makes for a really nice machine.

I'd do a VFD conversion myself, but I have a couple of the DC motors
underfoot and I like to play with old tech. (I'm also cheap and I
managed to get one of the KB controllers off of ebay a while ago)

I'd still look around for other examples. Shipping isn't that
bad; you ought to be able to find a really good one for a lot less
than $10K.

Paul


--
Paul Amaranth | Rochester MI, USA
Aurora Group, Inc. | Systems & Software
paul@... | Unix / Windows / NT