[TheForge] Frequency Converters

[Chuck Robinson]

I don't know how I could make one of those single phase AC motors variable
speed, except by changing drive wheel diameter.  What am I missing?
Variable speed control is paramount in my grinding operation.
Chuck
----- Original Message -----
From: "Steve Smith" <sos at alum.mit.edu>
To: "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Wednesday, September 22, 2004 6:15 PM
Subject: Re: [TheForge] Frequency Converters


> Well that explains a lot. Burden's is the place with all the good stuff.
> I thought the other URL was Burden's. Thanks for the correct address.
>
> Why not go with one of the single phase motors? They've got some 5HP
motors:
>
http://www.surpluscenter.com/sort.asp?UID=2004092218080590&catname=electric&
keyword=MBAL
> some of which are cheaper than your 3HP. Also, note that a VFD will cost
> you more than any one of the motors.
>
> Steve
>
> Chuck Robinson wrote:
> > Hey Steve,
> >  Wrong company.
> > The motor I'm looking at is at
> > http://www.surpluscenter.com
> > The motor would be used to drive a variable speed 2" x 72" heavy duty
belt
> > grinder for hogging out hammer billets.
> > All ready using a 2 hp dc motor and speed controller, But it stalls
under hi
> > load conditions.
> > Chuck
> >
> > ----- Original Message -----
> > From: "Steve Smith" <sos at alum.mit.edu>
> > To: "Sponsored by ABANA" <theforge at mailman.qth.net>
> > Sent: Tuesday, September 21, 2004 7:35 PM
> > Subject: Re: [TheForge] Frequency Converters
> >
> >
> >
> >>
> >>Chuck Robinson wrote:
> >>
> >>>Hey Folks,
> >>>I don't know my ass from my elbow about frequency converters, but the
> >
> > latest
> >
> >>>Surplus Center  flyer has  a Leeson 3 phase 3450 rpm motor advertised
> >
> > for
> >
> >>>$150. Item # 10-2041.
> >>>Is this a good candidate for FC controller?
> >>>If so what is a good source for the FC and approximate price?
> >>>Chuck
> >>
> >>Chuck, I'm not finding your motor on the Surplus Center's web page (I
> >>assume you mean http://www.surplussales.com/ ), so I can't help you
> >>there. It looks like their web page isn't fully cooperating with
> >>Mozilla. Note that used three phase motors (scrapyard, auctions) often
> >>go cheap.
> >>
> >>I think you're talking about a Variable Frequency Drive (VFD); a box of
> >>electronics which produces three phase (variable frequency) out of
> >>single phase or three phase. A good source is:
> >>http://www.dealerselectric.com/
> >>Note that they sell a package deal on a VFD and a motor. To see their
> >>VFD's, click on "Browse our Inventory" then "Variable Freq. Drives".
> >>They are very helpful on the telephone. I bought an FM100 from them for
> >>my mill (which of course I haven't had time to put in yet...). A couple
> >>of things to note about VFD's:
> >>1. You can't hook the VFD output up to a bunch of wiring with different
> >>machines on it. The VFD must drive your machine directly, not even using
> >>the switch on the machine (there are ways to work this, just not
> >>directly). Otherwise, the VFD can be damaged by a no-load condition.
> >>2. You can get units up to 3HP that will take single phase input and put
> >>out three phase output. Above 3HP, you need to derate by one step if you
> >>have single phase in. For instance, if you want to run a 5HP, 3 phase
> >>motor off single phase, you need to use a 7.5HP VFD.
> >>
> >>If you don't already have a three phase motor, it may make more sense to
> >>buy a single phase motor. This is probably cheaper than buying both a
> >>three phase motor and a VFD.
> >>
> >>Steve Smith
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> >
> >
> >
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