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

[Dave & Debbie Barden <daveb seanet com>]

Thanks for bringing me into the 21st century Rod!
My impression of AC motor applications came from a library book I've been 
reading by Mike Brown, "Convert It"  I just checked the publication date, 
1993.

dave
Seattle

> 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
> > 
> === message truncated ===
> 
>