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Re: (ET) ICE to electric conversion



Excellent feedback (below) from Darryl!   If I may, I'd just like to add a few more cents worth:
 
Universal MotorsI'd avoid universal motors.  Universal motors are truly nothing more than a series-wound DC motor with laminated cores (to deal with AC eddy currents) and a few fewer turns in the windings (to deal with AC inductive reactance.   Therefore, being nearly the same as a series-wound motor, its internal speed regulation (how well it holds constant speed under changing load conditions) really stinks.
 
"Forward" Rotation:  Standard forward rotation for electric motors is clockwise, when looking from the load toward the motor's shaft, or (of course) counter-clockwise when looking from the tail end of the motor toward the load.   Reverse rotation is easily doen by swapping the polarity of either the armature current or the field current...BUT...brush orientation and interpoles (compensating windings) may make running in reverse (for extended periods of time) infeasible.   Interpoles are sometimes built into DC motors to offset armature reaction in a variable load situation...but they tend to work much better in one direction than the other.   In fact, they may make reverse operation horrible.   Also, radially-aligned brushes (straight in toward the center of the shaft) are great for motors that will be run bi-directionally.   However, leading or lagging brush angles (the manufaturer will sometimes tip the top end of the brushes off the cross-section-center-line of the shaft) may also make reverse rotation pretty funky.
 
ICE vs. EM:  Darryl is right about the 4:1 ratio...lot's of folks will have different opinions on this.   The most common ration I've seen is 5:1; however, Darryl's 4:1 ratio (ICE hp to EM hp) is "safer," and I'd go work with that.
 
That's my two cents...Good Luck!
 
TJWilhelm
 
 
----- Original Message -----
From: "Darryl McMahon" <darryl econogics com>
To: <elec-trak cosmos phy tufts edu>
Sent: Sunday, March 07, 2004 12:30 PM
Subject: Re: (ET) ICE to electric conversion

> "Todd Lynch" <jd4020d_69 hotmail com> wrote:
>
> > Hi all,
> >
> > I have been watching the list for a while and have looked for an Electrak
> > for sale in southern Minnesota with little success.  With all the talk about
> > updating Electraks to use a more modern controller, I was think about how much
> > more it would take to convert an ICE garden tractor to electric.  I already have a
> > John Deere 112, of approximately the same era the Electrak was made, with a bad
> > engine, along with a mower, tiller, and sickle mower.  I was thinking of mounting
> > an electric motor where the current ICE engine is mounted to run the accessories,
> > and mount an separate motor by the transmission to drive the wheels, any thought?
> >
> > I would greatly appreciate any thought or recommendations you might have
> > such as size and type of motor would work best for this type of application
> > etc...
> >
> >
> > Thanks,
> >
> > Todd Lynch
>
> Todd,
> such conversions are certainly possible, and have been done.
>
> Some things to consider.
>
> Hydrostatic transmissions waste a lot of energy as heat (which is why they usually
> have lots of cooling fin area on their casings).  I don't know your proposed donor,
> but if it has a hydrostatic transmission, I'd look for another base for your
> conversion.  However, given it's vintage, I expect it is not hydrostatic.
>
> Every gas tractor I am familiar with uses a single engine for both traction and
> powering the devices.  You will need to size your electric motor accordingly.  Most
> electric tractors have used multiple motors; one for traction and one or more
> additional motors to power other devices.  Gasoline engine and electric motor
> rating
> systems are different.  Gasoline engines are rated on the maximum power they can
> produce under optimized conditions.  Electric motors are usually rated based on the
> power they can produce continuously for one hour, often under specific less-
> than-ideal conditions.  My rule of thumb is 4:1 - if an electric motor is rated at
> 1
> hp, it is roughly equivalent to a 4 hp gasoline engine for power.  Not everyone
> will
> agree with that.  For a lawn or garden tractor, I think you should be looking for a
> 2-4 hp electric motor.  For comparison, the electric motors used in golf carts for
> many years were nominally rated about 2 hp.  The electric motor will typically
> accept power demand over its ratings for short periods without problems - so long
> as
> it can disperse the waste heat afterward.
>
> Presumably you plan to power your tractor with batteries.  They are a DC electrical
> source.  Further, most tractor applications want relatively steady-speed operating
> capabilities.  Therefore, I recommend you look for a shunt-wound, compound-wound or
> separately-excited DC motor (rather than a series-wound motor or AC motor).  There
> are universal motors, but I have not encountered them in 10 hp (peak) and up power
> ratings.  Permanent magnet motors are usually equivalent to shunt wound and would
> be
> acceptable, but again, I'm not aware of many of the right size for a garden
> tractor.
>  I'm not going to be much help on sources, but I'm sure other listers can help out
> in that department.  While golf cart motors are about the right ratings, they are
> usually series-wound and often use a mated gearbox to provide bearing support for
> the output shaft, so are not usually good candidates for this sort of application.
>
> Power from the batteries to your electrical devices will be delivered in watts,
> which is volts x amps.  So for the same power, more volts means less amps.  Less
> amps means lighter gauge wires.  On the other hand, anything above 48 volts DC can
> be nasty.  The Coast Guard permits up to 48 volts around water without special
> permits.  The new generation of golf carts are standardizing on 48 volts.  The Elec-
>
> Traks and their brethren standardized on 36 volts.  The traditional golf carts
> standardized on 36 volts.  The next generation automotive accessory standard
> (sometimes referred to as 42 volts) is really a 36 volt nominal standard.  Much of
> today's materials handling equipment runs on 36 or 48 volts.  Many of the early
> electric cars (early 20th century) ran on voltages between 36 and 48 volts.  A lot
> of experience has led back to the same conclusions.  I recommend you benefit from
> that experience and stay with a voltage in the same range.  This will also provide
> you with some parts sources for various electrical components you will need
> (batteries, fuses, motors, contactors, controllers, chargers, etc).
>
> So, look for a motor with an operating voltage rating in this range.  Next, find
> out
> what the operating speed for the motor is at nominal voltage.  I expect you will
> want something in the area of 3000 rpm as the rated speed.  If it is signficantly
> different, you will likely want to do some belt and pulley gearing to get this
> effective speed at the point where your electric motor joins up to the transmission
> and power-take-off.  You might have lots of torque, but if the RPM is too slow, you
> won't be happy with the performance of your machine.  (If it's too fast, you'll
> have
> some different issues, but you still won't be happy.)
>
> While the venerable ETs used contactor and resistor controllers, I would recommend
> use of a modern solid-state controller if your budget permits.  If not, resistors
> and contactors will work.
>
> Don't skimp on gauges (voltmeter and ammeter minimum), fuses and at least one
> manual power disconnect.
>
> Most electric motors make electric reversing pretty simple to implement.  However,
> if your existing donor has a mechanical reverse in good working order, I would
> stick
> with that, and go with the simpler wiring that goes with running the electric motor
> in one direction all the time.
>
> The electric motor will have to be mounted to turn in the same direction as the old
> gasoline engine did.  I don't play with many small gas engines, but I think most
> spin counter-clockwise (CCW) as viewed from the output shaft.  And while most
> electric motors can be reversed, they usually do have a preferred direction of
> operation.
>
> Once you have a bit of a plan, or questions about suitability of components, I
> recommend you share them here.  There is a truly amazing amount of knowledge and
> ingenuity (and a little bit of lunacy) available here.  In general, a very helpful
> and sharing community on this list.
>
> These links might provide some inspiration.
>
>
http://www.austinev.org/evalbum/038.html
>
>
http://www.austinev.org/evalbum/196.html
>
>
http://www.austinev.org/evalbum/411.html
>
>
http://www.austinev.org/evalbum/065.html
>
>
http://www.austinev.org/evalbum/216.html
>
>
http://www.renewables.com/tracpage1.html
>
> Hope this was helpful.
>
> Darryl McMahon
>
>
> ------- End of forwarded message -------
>
>
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