Re: (ET) Solid state controls

["RJ Kanary" <rjkanary nauticom net>]

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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