Re: (ET) Solid state controls

["SteveS" <ssawtelle fcc net>]

Thanks for the explanation. So, there is a place for a solid state controller. Yet another idea I need to find $ and time for.

 

BTW, thanks to David for the link to the British outfit - looks like pretty decent stuff. Anyone used these?

 

If one were to go solid-state, what amperage would be needed? (E15 motor)

 

SteveS

E12S

----- Original Message -----

From: Bob Murcek

To:  ; ssawtelle fcc net

Sent: Tuesday, July 23, 2002 2:11 PM

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.


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