RE: (ET) Re: new electrics

[Dave & Debbie Barden <daveb seanet com>]

AC motors?  I thought they required a more complex/expensive controller?
Was there some kind of controller break through or is the controller not 
necessary because motor is constant speed??

dave
seattle

> Hyster, Yale, Toyota and Linde are going all AC
> across the board on their forklifts in the near
> future.  This will provide a good source for low
> cost motors and controls for riding mowers.
> I've even seen 24V walkies with AC induction systems.
> The major players in the motor control market
> are Curtis, Zapi and SME (Toyota makes their own).
> Rod
> www.qsl.net/w8rnh
> 
> --- William Korthof <wkorthof earthlink net> wrote:
> > The cheap batteries have been around for quite a
> > while...
> > golf cars have created this market: a pack of six
> > US2200
> > or T105 batteries cost just a few hundred dollars
> > (~$300).
> > 
> > I think the improved power electronics and motor 
> > choices
> > (in volume, a 3-phase inverter is cheap enough to
> > allow
> > use of 3-phase AC motor). An AC motor driven by
> > normal
> > vector drive inverter obviates the need for multiple
> > gears.
> > Regenerative braking is also easy with AC drive. All
> > the
> > above would result in significantly improved
> > efficiency vs
> > GE Electrak-era hardware.
> > 
> > Any necessary 12vdc accessories can be operated
> > directly from a DC-DC converter. Lighting and
> > markers
> > could use LEDs and compact fluorescent lamps.
> > 
> > Todays power electronics also make it easy to have a
> > powerful automatic charger that is "plug and play"
> > to a
> > standard outlet and provides most of a charge within
> > 2-3 hours. Faster, smarter charging, improved
> > efficiency,
> > and more completely balanced battery discharging
> > (vs electrak taps) would lower the AC power use,
> > extend
> > run time, and lengthen battery performance and pack
> > life.
> > 
> > In addition, todays inverters could easily provide a
> > nice
> > supply of 120 VAC for portable power tools.
> > 
> > I do think that a modern electric tractor is an
> > unexplored
> > product with a significant un-served market.
> > 
> > 
> > /wk
> > 
> > 
> > At 09:46 AM 2/20/04 -0500, Elie, Larry (L.D.) wrote:
> > >Hydrostatic is 65 to less than 80%, depending on
> > many factors including 
> > >temperature.  It's used on gas tractors for
> > connivence, nothing 
> > >more.  Hydrodynamic (car automatic) can go much
> > higher, but isn't really 
> > >variable speed at all; just shift-on go.
> > >
> > >It's always funny when our 30 year hindsight
> > realizes that people 30 years 
> > >ago weren't dumb.  If electric tractors rise again,
> > it will be because 
> > >someone has a cheap battery or ultra-cap... or
> > perhaps uses a cheap fuel 
> > >cell.  This market is already poisoned, and no
> > large marketing guy will 
> > >touch it.  Once business people 'know' that no one
> > will buy something, 
> > >they stop trying.  Another example:  Diesels have
> > 50% market penetration 
> > >in Europe at higher fuel price.  In the US it's 5%,
> > because GM failed 
> > >marketing it in 1980, and now everyone 'knows' that
> > no one will buy 
> > >them.  Service is part of that.  They tried, but
> > not well.  People paid a 
> > >large premium to buy the early ones, and then
> > averaged over $1,000/year 
> > >for repairs.  I'm afraid Honda or Toyota may poison
> > the electric market 
> > >for the next 25 years too.  If they start passing
> > on real their costs, 
> > >they will indeed kill the market.  I'm glad GM
> > pulled out before they 
> > >poisoned the electric market.  No one will take
> > large los!
> > >  ses for long before they pass them on or pull
> > out, and pulling out to 
> > > give others a chance is the BETTER choice for
> > everyone else.
> > >
> > >Larry Elie
> > >
> > >
> > >-----Original Message-----
> > >From: Ralph & Elaine Vogan
> > [mailto:ralphgv centurytel net]
> > >Sent: Friday, February 20, 2004 3:33 AM
> > >To: Elec-Trak
> > >Subject: Re: (ET) Re: new electrics
> > >
> > >
> > >Does anyone know the efficiency of a hydrostatic
> > drive?  Use a single speed
> > >motor and the drive for forward, reverse, and speed
> > changes.  I have an old
> > >White ice tractor with a very small hydrostatic
> > drive unit bolted to the
> > >differential.  It has plenty of power.  Or a
> > hydrolic pump & motor to drive
> > >the blades?
> > >
> > >Ralph V
> > >
> > >
> > > > With all this talk about new ETs and better or
> > cheaper ways to make them
> > > > please remember that due to the limited energy
> > storage on board our
> > >tractors
> > > > efficiency must be paramount.
> > > >
> > > > V belt drives tend to be only 90-95% efficient
> > when everything is in good
> > > > condition and clean.
> > > >
> > > > Friction drives are 80-90% efficient.
> > > >
> > > > Chains, again in good condition, are 98 %
> > efficient, but high maintenance
> > >to
> > > > keep them in good shape in a tractor
> > application.  Notice that they are
> > >not
> > > > used except in high torque attachments like the
> > snowblower.  A worn, dry,
> > > > and/or rusty chain can have efficiencies as low
> > as 60-70%.  The wasted
> > > > energy turns to heat and destruction of what is
> > left of the chain and
> > > > sprockets.
> > > >
> > > > Direct drive, like the mower decks, are 100%
> > efficient.
> > > >
> > > > GE used VX series V belts for the traction motor
> > because the VX series V
> > > > belts are more efficient than the old A/B/C/D
> > series V belts.  If the new
> > > > Poly V belts, which are like the serpentine
> > belts on modern cars, had been
> > > > available when the Elec Traks were designed they
> > would have been used
> > > > preferentially over VX belts.
> > > >
> > > > What GE did was make a whole series of design
> > choices to keep efficiency
> > > > high.  Where they lost efficiency was in the
> > motor controls, and that was
> > > > mainly a limitation of affordable DC drive
> > technology of that time.  If
> > >you
> > > > were, in your new tractor, to use a friction
> > drive for the traction motor
> > > > and belts in the mower deck, and then allowed
> > for lack of maintenance,
> > >you'd
> > > > find extra losses of 10-25% after 1 or 2 years
> > of service.  I mean 10-25%
> > > > higher losses than in a tractor with direct
> > drive to the blades, and a
> > >high
> > > > efficiency belt somewhere in the traction drive.
> > > >
> > > > With respect to protecting the mower motor with
> > a circuit breaker:  This
> > > > will not work well with a permanent magnet
> > motor.  In permanent magnet
> > > > motors there is some critical armature current
> > above which you will
> > > > demagnetize the magnets.  The friction washers,
> > while crude, act as a
> > >torque
> > > > limiting clutch.  By limiting torque, you
> > effectively cap the armature
> > > > current.  If you use a circuit breaker alone the
> > current can, and most
> > > > likely will, pass well above that critical
> > current before the breaker
> > >trips.
> > > >
> > > > Steve Naugler
> > > > snaugler earthlink net
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > Elec-trak mailing list
> > > > Elec-trak cosmos phy tufts edu
> > > >
> >
> https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak
> > 
> === message truncated ===
> 
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