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 02-27-2008, 11:22 PM #1 (permalink) TomEV Ford Escort 2.0     Join Date: Feb 2008 Location: Alameda, CA Posts: 240 Electricar - '89 Ford Escort LX Hatchback Thanks: 6 Thanked 27 Times in 24 Posts Series Motor - Speed vs Torque I came across a statement regarding the correct connection of the field and armature posts on a series DC motor. One thing that I found interesting was this: "where a series field (S1 and S2) is provided, the polarity of this winding must always be connected for the same polarity of the motor armature" "Apply + and - to the same number post. + to A1 and S1; - to A2 and S2. It's A1, A2+S1, S2 for torque, but A1, A2+S2, S1 for speed" So, from a line drawing perspective, it would look like this: + A1::A2>>S1::S2 - for torque (where :: is the motor internal wiring, and >> is either a jumper wire or a Forward/Reverse contactor) +A1::A2>>S2::S1- for speed. Turns out that my motor was wired this way - +S2::S1>>A2::A1- (which would be a torque setting, forward rotation) In order to test out the 'speed' theory, here was my plan. First step is to change to 'speed' +S1::S2>>A2::A1- (ends same - speed) But this would reverse the motor rotation, so I reversed the polarity at the ends: -S1::S2>>A2::A1+ (ends still same - speed, opposite polarity = forward) Oddly enough, the car went BACKWARDS in this configuration. I checked it several times to make sure I wired it according to the diagram. I did. Well, no harm, no foul - I just switched it to 'reverse' and drove home. Same acceleration, same top speed In 'reverse' it swaps S1 and S2, so: -S2::S1>>A2::A1+ (torque mode... ends opposite.) Essentially the way it was. Back at home, I changed the polarity on the ends to make it 'go' the other direction - +S1::S2>>A2::A1- Again, the car went BACKWARDS Anyone out there have a spare series motor on the bench that can tell me if their motor turns the same direction if polarity is swapped in these two cases? I may pull out my motor to see, but if someone has one out already, it would save me some confusion... +S1::S2>>A2::A1- -S1::S2>>A2::A1+ Seems no matter what I do, this setup wants to be in torque mode forward, and speed mode reverse (the opposite of what I want to test). The saga continues! __________________