Re: (ET) Alltrax install!

["David Roden (Akron OH USA)" <etpost drmm net>]

On 23 Feb 2006 at 1:19, Ralph & Elaine Vogan wrote:

> look at the wiring diagram for the Alltrax.  You will see the SEAT
> SW., KEY SW., & BRAKE SW. are wired to the MAIN CONTACTOR.  Turning off
> any of these will turn off the power to the Alltrax unit. 

I have that very diagram right here on my computer. If you need a copy, 
you 
can download it from here :

http://www.alltraxinc.com/old/Manuals/DCX-ET%20Manual.zip

Just expand the compressed archive and you'll find the diagram as a .bmp 
file, which should be readable with most graphics programs.

According to the diagram, those safety switches connect to the KSI 
(keyswitch) input of the controller (6th pin from the left), not to the 
main 
contactor.

Battery voltage on the KSI terminal enables driving current from the 
controller. 
 Any time the main disconnect is on, battery + is also applied to the 8th 
and 
9th pins (designated logic B+ and B+ power respectively).  These are 
supplied from a tap *ahead* of the main contactor.  The main contactor 
coil is 
powered by an output from the controller, not directly by the keyswitch.

Those pins (8 & 9) are specifically intended to be powered *even when the 
KSI terminal is not* so the controller can stop the tractor as quickly as 
possible under the following circumstances - 

        1. the brake is applied

        2. the keyswitch is shut off

        3. the operator leaves the seat

It uses plug braking to do that.  I have experienced this effect on my 
tractor.  
If I want it to stop quickly, I just turn off the key or touch the brake 
pedal.  
The braking effect is quite pronounced!

If yours doesn't behave this way, either you didn't wire it according to 
the 
diagram, or plug braking has been disabled in your controller.  I think 
you can 
disable plug braking with the PC control program if you want to, but it's 
been 
quite a while since I ran that program on mine, so I'm not sure.

I may be wrong, but my understanding of plug braking is that it does not 
actually apply reverse current.  Rather it maintains the field current 
while 
short-circuiting (or nearly so) the armature.  This stops the motor very 
quickly.  If I'm wrong about that, I certainly welcome correction of my 
misapprehension from the designers of the Alltrax, the designers of any 
other 
plug-braking controller such as a Curtis, or those who have studied plug-
braking controller design.

My 115 volt push mower uses plug braking, not a mechanical brake.  It's a 
PM motor, and when the mains switch is opened, it closes the contacts 
across the motor armature leads.  The motor stops very quickly, I would 
say 
within a half-second or so.  This is exactly the same method GE used to 
stop the PM mower motors on the deck.

> I am sorry if I offended anyone, that is not what I am trying to do here.

I don't know about anybody else, but I'm not at all offended.  You don't 
need 
to SHOUT, though.  ;-)

David