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Ditto. The E12 can go
full forward to full reverse and back and not die. I ran without brakes
for years this way.
Larry Elie
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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