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Re: (ET) RE: Alltrax DCX300 availability - Field current

RJ is correct, however even the 4 interlocks can take damage over time. There is a MOV on the field resistor board that acts as a snubber to keep the arcs to a minimum, however I did note last year that 2F on my tractor was dropping a lot of current. Turns out the resistance increased due to years o' arcing, causing the plastic insulation around the post to melt.
The E15 model in my opinion was a lower cost version of the E20 system by dropping the 4 contactors in favor of field switching. Not as good an idea. Now an interesting question is what happens if you reverse the *field* using a 4 contactor arrangement, not sure what happens there.
Cleanpower has the retrofit kits if I recall correctly. It looks like a good solution. 

Chris


RJ Kanary wrote:


One curiosity that I don't understand is why, on the
E20 BA and CC, they used an H bridge of 4 mechanically
interlocked heavy-duty contactors to reverse direction
via the armature when they could've achieved the same
with a single dpdt relay reversing the field.
The answer is quite simple. Look at all the reports of reversing relay failures. Repeated ones. The field reversing control systems just don't respond too well to operator error, regardless of how inadvertent it may be. The armature reversing scheme, while more expensive, has proven to have the edge in reliability. 
At least that is my observation over the past twenty five or so years.
GE eventually simplified the scheme, using two four terminal armature contactors, with the same rate of reliability. Bill Gunn even marketed an update kit, to retrofit the older models at a considerable cost savings. 






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