Re: (ET) Solid state controls

["Christopher Zach" <czach computer org>]

Hm. How about having the relay switch a quadrant of solenoids which would
then reverse field current? Firing two solenoids for fwd and two for 
reverse
shouldn't be too hard, and the solenoids would handle the back-current
better.

Chris

----- Original Message -----
From: "RJ Kanary" <rjkanary nauticom net>
To: <elec-trak cosmos phy tufts edu>
Sent: Tuesday, July 23, 2002 8:24 PM
Subject: Re: (ET) Solid state controls


> Here is the rundown on control schemes, for each model. Later 
> alphabetical
> suffixes, indicate later production.
>   E 12 S, AA & BA    Field Reversal
>    E 15 ,   AA to GA     Field Reversal
>      E 15  , HA , and later   Armature Reversal : Single Coil Contactors
>        E 12, {Not 'S' } C & D   Armature Reversal : Twin Coil Contactors
>          E 20 , AA to DA  Armature Reversal : Twin Coil Contactors
>            E 20,  EA, and later    Armature Reversal, Single Coil
> Contactors.
>            The reversed field models, have always seem to have the relay
> blasted. Even installing varistors, across the contacts, seem to extend
life
> by only a few years.     It would appear, after all the votes were in,
that
> the "Progress Is Our Most Important Product" ® people decided that the
relay
> was not the way to go. Today, some sort of solid state replacement, may 
> do
> better, in that nasty environment.
> RJ Kanary
> Member TRNi  Since 1998
> ASE® Certified Master Auto Technician
>
> rjkanary nauticom net
>
> ----- Original Message -----
> From: "Christopher Zach" <czach computer org>
> To: "RJ Kanary" <rjkanary nauticom net>
> Sent: Tuesday, July 23, 2002 7:43 PM
> Subject: Re: (ET) Solid state controls
>
>
> > Ah, interesting. I always thought my E20 was an older model; all the
later
> > E15's seem to have the non-solenoid system.
> >
> > It's probably a lot cheaper to go with one relay and reverse field than
it
> > is to reverse the 100-200amps of the armature.
> >
> > Chris
> >
> > ----- Original Message -----
> > From: "RJ Kanary" <rjkanary nauticom net>
> > To: "Christopher Zach" <czach computer org>
> > Sent: Tuesday, July 23, 2002 5:37 PM
> > Subject: Re: (ET) Solid state controls
> >
> >
> > > A 'Time Line' note, on traction motor control. All the later
production,
> > > large frame tractors, regardless of traction motor type, used the
> armature
> > > contactor reversing scheme.If there was any cost savings, using the
> field
> > > reversing method, it must have been minimal, compared to the
production
> > > savings, using the same armature control array, on all models. One of
> the
> > > durability tests, used in demonstrations, was to intentionally go 
> > > from
> > flat
> > > out forward, to reverse, and smoke the tires in the process.
> > >
> > >
> > > RJ Kanary
> > > Member TRNi  Since 1998
> > > ASE® Certified Master Auto Technician
> > >
> > > rjkanary nauticom net
> > >
> > > ----- Original Message -----
> > > From: "Christopher Zach" <czach computer org>
> > > To: "Pieter Litchfield" <plitch attglobal net>;
> > > <elec-trak cosmos phy tufts edu>
> > > Sent: Tuesday, July 23, 2002 4:38 PM
> > > Subject: Re: (ET) Solid state controls
> > >
> > >
> > > > Yeah, the E15 does things differently than the E20. On the E20, 
> > > > they
> > > reverse
> > > > the armature current using a pair of push-pull solenoids. On the
E15,
> > they
> > > > reverse the field current using a DPDT relay.
> > > >
> > > > The problem is when you go from fwd to reverse in the E15, the
> back-emf
> > > from
> > > > the armature surges the contacts and burns the daylights out of
them.
> > When
> > > > you go from fwd to reverse on the E20, the arc is absorbed by the
> (much
> > > > larger) solenoid breakers. Plus the field current is relatively 
> > > > weak
> > > anyway.
> > > >
> > > > But the E15 design is a lot less expensive; I guess that's why they
> > > migrated
> > > > to it.
> > > >
> > > > Chris
> > > >
> > > > ----- Original Message -----
> > > > From: "Pieter Litchfield" <plitch attglobal net>
> > > > To: <elec-trak cosmos phy tufts edu>
> > > > Sent: Tuesday, July 23, 2002 4:06 PM
> > > > Subject: RE: (ET) Solid state controls
> > > >
> > > >
> > > > > As the owner of the E-15 with bucket loader that loves to eat
> relays,
> > my
> > > > > suggestion would be that whatever controller is designed, be sure
it
> > can
> > > > > withstand the abuse hard use will heap on it.  For example, my
> > tendency
> > > to
> > > > > rapidly shift from reverse to forward while using the bucket has
had
> > > dire
> > > > > consequences for my relays.  A better design could improve on 
> > > > > this
> > > > behavior,
> > > > > or at least prevent the idiot behind the wheel from making the
quick
> > > shift
> > > > > ( a timer or charge-up delay circuit?)
> > > > >
> > > > > As a gross observation, my E-12 while not as elegant a control
> design
> > > > seems
> > > > > far more robust than the E-15.  At least I haven't cooked relays
> there
> > > > yet.
> > > > > But this does suggest that a prime characteristic of a power
control
> > > > system
> > > > > for an E-15 ought to be "robust-ness" and "fault tolerance."
> > > > >
> > > > >  -----Original Message-----
> > > > > From: owner-elec-trak cosmos phy tufts edu
> > > > > [mailto:owner-elec-trak cosmos phy tufts edu]On Behalf Of Bob
Murcek
> > > > > Sent: Tuesday, July 23, 2002 2:11 PM
> > > > > To: elec-trak cosmos phy tufts edu; ssawtelle fcc net
> > > > > Subject: Re: (ET) Solid state controls
> > > > >
> > > > >
> > > > >   Steve,
> > > > >   No, reducing speed with a soild-state controller does not cause
> loss
> > > of
> > > > > torque.  On an E12 at least the 1st and 2nd "speeds" are created
by
> > > adding
> > > > > resistors in series with the armature circuit.  When the armature
> > > current
> > > > > tries to increase, say to go up a hill, the voltage drop across
the
> > > > > resistors increases, causing the motor to slow down.  Since the
> power
> > > lost
> > > > > in the resistors is wasted, resistor-based speeds should only be
> used
> > to
> > > > get
> > > > > going smoothly.
> > > > >
> > > > >   Solid-state controllers turn the power in the armature circuit
on
> > and
> > > > off
> > > > > rapidly (not sure of the rate, but it's apparently supersonic in
> > mine),
> > > > > varying the ratio of the on time to the off time to control the
> > average
> > > > > voltage seen by the motor.  There's very little waste since the
> > > > solid-state
> > > > > switch is either on or off.  When you go uphill with a 
> > > > > solid-state
> > > > > controller and the armature current tries to increase, it's free
to
> do
> > > so
> > > > > during the times when the controller is in the on state, so a
> slowdown
> > > > > doesn't occur.
> > > > >
> > > > >   Possibly the biggest advantage of a solid-state control in an 
> > > > > ET
> is
> > > the
> > > > > extremely fine and smooth control at very low speeds, like when
> taking
> > > up
> > > > a
> > > > > load or parking in a tight spot...Bob
> > > > >
> > > > >
> > > > >   >>> "SteveS" <ssawtelle fcc net> 7/23/2002 1:39:55 PM >>>
> > > > >   Ah, good explanation. I see now how it makes sense on an ICD
> mower.
> > > With
> > > > > my
> > > > >   E12S, with 'only' 3 speeds forward X 4 gears, I still have
pretty
> > much
> > > > all
> > > > >   the control I need. I do find, however, that any speed less 
> > > > > than
> > full
> > > > >   throttle has poor power. I can climb a hill in full throttle
that
> > > stalls
> > > > > out
> > > > >   on lower settings (same gear). That seemed illogical at first,
but
> I
> > > > > assume
> > > > >   it's because the motor has less than full armature current. 
> > > > > Does
> the
> > > E20
> > > > >   have the same characteristic?
> > > > >
> > > > >   I presume a solid state control would have the same effect
(lower
> > > > settings
> > > > >   for slower speed sacrifice power as well)?
> > > > >
> > > > >   SteveS
> > > > >   E12S
> > > > >
> > > > >
> > > > >   ----- Original Message -----
> > > > >   From: "Christopher Zach" <czach computer org>
> > > > >   To: "SteveS" <ssawtelle fcc net>; "Elec-trak" <>
> > > > >   Sent: Tuesday, July 23, 2002 12:49 PM
> > > > >   Subject: Re: (ET) Solid state controls
> > > > >
> > > > >
> > > > >   > Hydrostatics are nice on an ICE based mower because you
usually
> > have
> > > > to
> > > > >   run
> > > > >   > the engine at full speed in order to keep the blades 
> > > > > spinning.
> > > > >
> > > > >
> > > > >   -- snip snip snip
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
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