I need some help explaining a motor I have been using for over a year. It is a shunt field motor. Please stick with me as I develop the situation. If you know of better place to ask me question please let me know. (forums?) I have a shunt field motor that I have been using with a series field controller. I have been using this on an electric gokart and it has worked fine for over a year. Shortly after finishing the wiring and testing (it ran great btw) I realized I made an error when wiring the shunt. I wired it so no current flowed in the shunt, The wiring put a 20 ohm resistor across the shunt. Here's a simplified schematic of the wiring. The 20 ohm resistor is for current limiting, as I'm overvolting the motor.I wired it properly and the motor ran slower, so I ran the shunt open and this cause my controller to become defective ( bad day). After I got the controller fixed I wired it as original (no shunt current) and we have drove it for a year. Here's a link showing all three wiring diagrams.
So, how does this even work with the shunt wired to the 20 ohm resistor and not current through the shunt? I expect some answer about current induced by rotor flux, but we'll see.
Next problem, the motor smoked the other day, I pulled it apart and found the field overheated. The field has 4 poles and is a bit odd. Two poles use #16 wire and two use #24 wire. The field measures 41 ohms and has not changed in the last year. I can't tell if the #16 and #25 are series or parallel, however, I think it is a good guess they are in series because I think the #16 wire fields would have much less than 41 ohms. The fields do show opposite magnetic fields as I go around the stator. (Tested with small magnet on a stick). Here's a picture of the stator with two different wire sizes. Note three different color wires in #16 wound field.
I understand the motor could have compound or interpole windings, but I don't think either of these are true, based on my measurements. Here's a diagram of the motor connection. Only three wires out labeled A2, F1 and F2.Here's the original motor wiring plate, I don't think it is relevant because it is clear this motor has been rewound. So, Why the different size wire in the field?
The #24 wire is overheated at one end of the motor, any idea why it would have overheated, since I don't battery current through the shunt?
I will be happy to do any more measurements requested if I can.
Any help to enlighten me is appreciated. Thanks, MikeK