Re: Need a variable-speed 2hp or greater AC motor for serious gap drive

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jeremy Scott by way of Terry Fritz <teslalist-at-qwest-dot-net>" <supertux1-at-yahoo-dot-com>

If you don't mind DC, www.sciplus-dot-com has a 2HP 120V
4800 RPM DC motor (from a treadmill I think.) Tricky
part there is getting the thing to spin at the right
speed and phase adjustment. I bought one and am
currently designing a digital IGBT/MOSFET drive for
it. Speaking of which, I'm looking for something
(chip/circuit) that provides at least 10 (preferably
16) bit PWM. The BS2p's PWM command is sorely lacking
the resolution for accurate speed control.



--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Nick Andrews by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <nicothefabulous-at-hotmail-dot-com>
 >
 > Well, the squirrel cage on a swamp cooler (evap) is
 > pretty good size and
 > spins fairly fast, and they are driven by 1/4 up to
 > 1-1/2hp motors just
 > fine.  And they (obviously) move a fair bit of
 > air...  Much larger and more
 > rotating mass than most rotor discs I've seen.
 >
 > Nick A
 >
 >
 > >From: "Tesla list" <tesla-at-pupman-dot-com>
 > >To: tesla-at-pupman-dot-com
 > >Subject: Re: Need a variable-speed 2hp or greater
 > AC motor for serious
 > >gap drive
 > >Date: Mon, 02 Jun 2003 06:33:03 -0600
 > >
 > >Original poster: "W.R. Langston by way of Terry
 > Fritz
 > ><teslalist-at-qwest-dot-net>" <blangsto-at-iwvisp-dot-com>
 > >
 > >Dan,
 > >
 > >Funny you should ask. My son, the currently
 > practicing physicist
 > >(government paid research physicist -- a shade too
 > accustomed to the
 > >concept of over-engineering IMHO ;-), has machined
 > as close to a
 > >bulletproof rotary gap as my eyes have ever set on.
 > Somehow he has managed
 > >to get almost all the people in his section excited
 > about this project and
 > >directly in on the design and machining work -- if
 > you've ever worked in a
 > >government lab, that should explain everything
 > about what is going on here.
 > >It looks like it will require 1 1/2 hp to cause
 > this thing to quiver, let
 > >alone spin. However, once in motion, it should be
 > able to reverse feed
 > >Hover for a few seconds as it slows down.
 > >
 > >If there has ever been something that looked
 > virtually indestructible,
 > >this is it. Once it is all together, I'll post a
 > photo. One picture is
 > >worth a thousand poetic phrases. The base and
 > standups are all 1" alloy,
 > >the shaft is 1" SS round stock. It is electrically
 > isolated (read that
 > >"insulating belt driven"), and the disc is 1" x12"
 > G11. Last time I looked
 > >at the design, the electrodes were to present a
 > hemispherical, 1/2" face
 > >to each other -- set at an appropriately calculated
 > angle to allow for the
 > >burn-off of early arc and/or late quenching to wear
 > uniformly (I'm betting
 > >that part of the plan will just never work, what
 > with windage and random
 > >heat transfer and magnetic field effects on the arc
 > and all).
 > >
 > >At any rate, I cannot change his mind to down size
 > the thing, so it fell
 > >to me to come up with a variable speed control for
 > the 1 phase, 240v, 2 hp
 > >motor we have now, or a motor and control to suit
 > whatever can get the job
 > >done.
 > >
 > >So, thanks for your input, I'll pass it on to the
 > "team." You see, I am
 > >over 50 (one foot in the ground already and the
 > other on uncertain
 > >footing), no longer in an "official" lab... so what
 > do I know -- about
 > >anything -- in the face of the educated, under
 > thirty crowd????
 > >
 > >Oh well, he is my retirement plan, so I guess I'll
 > humor him ;-)
 > >
 > >Have a great day,
 > >Bill L.
 > >
 > >Tesla list wrote:
 > >
 > >>Original poster: "by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>"
 > >><dhmccauley-at-spacecatlighting-dot-com>
 > >>
 > >>
 > >>If you need one in a hurry, you probably can't be
 > too picky in what you pick
 > >>up used.  Best bet is to check out Grainger-dot-com.
 > >>They have a very large number of universal motors
 > / induction motors from
 > >>the fractional range up to the hundreds of HP.
 > >>
 > >>Why do you need one between 2 and 5 hp for 15-25
 > kW.  I've typically seen
 > >>less than 1HP universal motors used on 15-25kW
 > sized ARSG.
 > >>Unless you are making a HUUGGGEEE rotor, than i
 > think a 0.5-1.0HP motor
 > >>would suffice.
 > >>
 > >>Dan
 > >>
 > >>
 > >> > Hello folks,
 > >> >
 > >> > Do any of you have a source for either a
 > universal type AC motor of
 > >>between
 > >> > 2 and 5 hp, or a variable speed (chopper-type?)
 > controller usable for a 2+
 > >> > hp induction motor? We need to have built and
 > tested an ASRG for 15-25 kW
 > >> > by July 1st.
 > >> >
 > >> > I suppose a suitable sized, and cool-running DC
 > motor (speed controllable)
 > >> > would work well enough too.
 > >> >
 > >> > We have the machining and structural aspects
 > well enough in hand, but
 > >> > finding a large enough, variable speed motor
 > has proven very difficult.
 > >> >
 > >> > We need to find one or the other asap.
 > >> >
 > >> > Thanks,
 > >> > Bill L.
 >