Well, hm.I checked the voltages on the 4 pin D sub connector that goes to the E20 motor. Two of them are a thermal switch, the other two are the field. Identifying which ones are which is a bit complex, but I was able to test resistance on the motor end and see which ones were the switch (0 resistance) and field (18 ohm resistance).
Then the interesting part, checking voltage. With the D sub unplugged the thermal switch showed 40 volts with key on, 0 volts key off (ok, but odd the controller contactors work with it unplugged from the motor, need to check that) and the two from the field showed 18 volts.
Even with the tractor switch off. Even with the disconnect turned off. They change when field weakening is engaged, going up to the 30's, and that is ODD.
Ohhkay. Somehow I may have a second ground fault in the system, greeeeat. I know that my E20 motor armature field coil (the big one in parallel with the armature) *does* have a ground fault and aside from chucking the motor I'm not sure what can be done. However a second ground fault could be causing field current to be drawn through the motor armature, then the field. This could explain why the batteries drain when the tractor is sitting for a week or two....
Pulled card 4 and checked the 4 diodes that handle the field (and go bad from time to time). All showed .5 volt drop in the proper direction, open the other direction (good). So it's probably not card 4. The 18 volts is odd, the lift is wired for 36 volts so it's not there. Might be the light circuit which is currently screwed up.
Still I think the motor is unhappy. I may try it with an external 12 volt battery to armature and field with the wires all disconnected and see if it spins at all. If it cogs, then the problem is in the motor and down it comes (probably to be replaced by an E15 motor while I decide what to do). If not then the apollo era controller has some explaining to do....
C On 2/5/2023 9:16 PM, RJ Kanary via Elec-trak wrote:
An open field circuit comes to mind............ RJ On 2/5/2023 6:51 PM, Chris Zach via Elec-trak wrote:Tractor started "cogging" last week with the drive motor, then would not start. 36 volts at the armature, cruise locks in the right relays. Moved the pulley a bit and the motor started.Great. Something is up in the motor. I'd guess brushes, but oddly enough I overhauled the motor in the last 10 years. Maybe 5. So something is odd.Motor drop this week, will see what's up. Maybe I'll just swap in the motor from the E15.C _______________________________________________ Elec-trak mailing list Elec-trak cosmos phy tufts edu https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak