RE: (ET) Re: new electrics for a mower

[Rod Hower <rodhower ameritech net>]

AC motors and controls were always attractive since
they don't require brush replacement (hence the motors
can be placed anywhere, buried).  They also offer easy
regen capability without contactors or extra silicon.
They also eliminate all of the contactors except a
main
line contactor for safety.  The draw back has always 
been the cost of semiconductors since you need six
times the number of switches (6 for a 3 phase motor
compared to one low side switch for a series motor).
Mosfet's have advanced considerably in the past 15
years and offer a system trade off cost that is
attractive.  Regen is very important on a forklift
that
spends considerable time reversing.  This is also
important on the lift system since regen can be used
to recapture energy as the load is lowered (instead of
using wastefull hydrolic valves that dissipate the
energy as heat.)  DSP's and microcontrollers tailored
for AC inverters are common place and innexpensive
(not
the case 15 years ago where a complex analog system
would be required).
All of these advantages can be applied to a new and
improved Elec Trak.
Also, the manufacturing cost of an AC induction motor
is inherintley cheaper than a brush motor.  The only
thing that will wear out on these motors is the
bearings, which should outlive the forklift.
If a good battery balancing system is used on an
electric mower, charging should be a no brainer, no
maintanence item.  I think an EV mowor is truely
cheaper to produce than an ICE version if quantities
are high enough.
I don't think a die hard ICE racer would prefer a loud
and smelly mower compared to an EV if the price was
right.
I just wish this country was more committed to
creating
alternatives like this to reduce pollution when the
outcome is more desirable to the average consumer.
Rod.
--- Dave & Debbie Barden <daveb seanet com> wrote:
> 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
> 
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