First of all, let me say hello to everybody as this is my first post to this forum although I have been following the VESC project for around 2 years. I have only been using VESC tool for Android along with the new bluetooth 4.0 module. All references I make to VESC tool are for the Android phone version. My hardware consists of 2 original VESC 6.6's from Trampa connected through CAN, and the BLE module.
I have already run the FOC wizard and got my motor working, but I want to make sure I have given the wizard the correct parameters for optimal operation and a correct speed reading. My motors are not typical; each motor is actually 2 Ninebot scooter in-wheel motors side by side. The stators are keyed to the same orientation on shafts I machined from 4340 steel to accommodate both stators. The rotors are coupled together with an aluminum spacer that orients the magnet poles in line. The mechanical alignment allows me to run 2 motors (with the phase wires connected in parallel) using the hall sensors from only one, and with only 1 VESC. This theoretically doubles the torque output from each wheel with the added benefit of the wheels looking like the double tires on the batmobile! It also takes better advantage of the power capabilities of the VESC6 hardware, which was my original motivation for doubling-up.
I don't know the KV of these motors, but I believe the scooters they came from are rated at 300 watts. However, I also think that number comes from the limits of the original controller because the (double)motor I already set up can draw up to 59 amps according to VESC tool. At 41.7 volts (battery voltage during testing) this works out to 1230 watts per motor. That is not a continuously sustainable current draw, but rather the max surge amp draw that can occur. My battery is custom built with Panasonic NCR18650 cells in a 10S9P configuration giving 27Ah capacity.
When I ran detection on the first motor, I used the following setup parameters:
- Type: Large outrunner
- Power loss changed to 150W from the default 200 (I was scared of frying motor)
- Motor poles: 15 (this is one setting I'm a little confused about. I will explain below)
- Sensorless ERPM left at default of 4000
- Openloop ERPM left at default of 1000
I am unsure if I should run the detection with "power loss" set to 600. My reason for doing so would be that these motors are designed to run at 300W continuous, and I have 2 coupled together. But after seeing that the E-bike hub motor (a similar motor type) is set to only 75W, the warning message has me scared I will fry the motors if I change the setting that high. I don't know the final effect this setting has on the available power output, but I assume that if the detection can't run the motor at its max safe current, the final power output will also be limited. Am I correct in that assumption? Is this setting asking for the power rating of the motors?
The other thing I'm confused about is the number of poles. The reason I'm confused is that elsewhere in VESC tool (I think it was somewhere in the motor settings page), the number of poles that can be selected can only be changed by factors of 2. But in the detection settings, the number of poles can be changed by factors of 1. My motors have 30 magnets... 15 pole pairs. Should I set it to 30, or 15? If it should be set to 30, then VESC tool should be changed to only allow this number to be even, like it is elsewhere in VESC tool.
And what is the effect of changing the "openloop ERPM" and "sensorless ERPM" values on the final motor parameters? Does a higher value change the max ERPM output when detection is complete, or does it just make sure the motor can start spinning synchronously during the detection without sensor feedback?
These settings are probably easily recognized and set by a person who has taken an electric motor design course, but I have not. I'm not a dummy, but I'm also not an electronics engineer. I'm somewhere in the middle of the competence scale with electronics. Its a hobby, and I have no formal training. But I do have 35 years or so of experience with repairing and using electronics and automation control systems.
I look forward to sharing pictures of this crazy build when it is complete. It will have independent 8cm swing-arm suspension, hopefully reach 68kph and be mostly silent due to the in-wheel direct drive motors. I want it to exceed a stock Bajaboard G4 in speed and power performance although it is being designed for mostly pavement riding (with the suspension for handling jumps off stairs and curbs and stuff).