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This deal about the reverse relay being damaged by
changing while moving has had me wondering since I first started following this
group. Theoretically, I think, the shunt field is just an electromagnet,
so there really shouldn't be any change in its electrical characteristics due to
the motor being energized, moving, etc.
I've heard lots of evidence to the contrary here, so theory must not quite
apply! I could imagine that maybe the construction of the motor isn't
perfect so there's some interaction with the armature's field. Or maybe
the series field is muddled up in this.
Any serious DC motor people out there know what's going
on?!
>>> "Pieter Litchfield" <plitch attglobal net> 6/7/2002 8:24:37 PM >>> Gang: My e-15 w/bucket loader has a nasty habit of eating the reverse relay - it welds or fries the contacts while in reverse, or when switching from reverse to forward modes. Over the past several years it has eaten 3 or 4. I am now using the improved Bill Gunn relay, and while definitely stronger, the tractor's demon is stronger still. I had assumed that perhaps the motor of a rolling tractor acts as a generator and that shifting too quickly from reverse to forward might allow the motor to weld contacts (or something). I do notice a spark when the rely breaks contacts with the reverse contacts if I shift it without the motor coming to a standstill, even with the tractor in neutral. No spark seems to occur when the motor is completely stopped. However, this could just be coincidental with something else - like a component that looses a charge over a short time. I do have the complete "homeowner's repair manual", but I ain't no engineer, so I look at the pretty pictures of wires and remain more or less clueless. I'll ask Bill when I order more relays, but does anyone else want to venture a suggestion as to why I eat relays? Thanks! |