Hi,
is it possible to use 2 motors mechanically connected at the same shaft (each controlled by its own ESC)?
How would the encoder wiring look like and can you estimate the output power as the double of one motor, or do you get more losses (syncing, ringing)?
Due to high amps, heating issues and too low torque I would like to put two motors in parallel.
In my world of little knowledge I would expect the amps to drop to about the half (okay just a little bit more due to double bearings losses e.g.) for each motor but the same power output at the end of the shaft.
How will calibration work? both motors mounted on the shaft? Each separate on the bench?
Thanks,
Chris
Chris, yes you can put two motors on the same shaft. Especially when both are driven in "current mode". You should NOT put them into say dutycycle or speed-control. In that case, slightl differences between the two controllers or motors may "explode" and cause wild differences in the amount of power each motor is delivering.
I probably mis-interpret your "amps to drop by half". As written I don't agree with your statement. With two (identical or similar motors) you're going to get double the torque for double the amps, i.e. the same torque-per-amp number. And to get the same output power, you need the same amount of current (total, shared between the two motors of course).
If the shaft and the other motor is light, calibration might work in the final setup. But I would recommend that you try the calibration step first before you mount the motors, and be sure to stash the numbers somewhere safe. Now you can experiment with trying it with the motors attached, but as a fallback you can always load the settings you got earlier.
The advantage of calibrating in the final setup is that for example the cable resistance from the controller to the motor counts towards the resistance that should be accounted for. So testing with the final cabling is preferable.
You can actually drive both motors with a single controller. If you use two of the same motor and align the phases electrically, they can be driven in parallel.
To do this, you could lock one motor on the shaft and leave the second unsecured. You connect the motors in parallel, and apply current to one phase. The motors should be held in a position by this current. Now you can lock the second motor to the shaft, so that both motors will always stay in sync.
Could you trust in the fact that the 2 motors are the same?!
Are you sure that the length and diameter of the winding wire is the same (resistance)?
Are you sure that the magnetic circuit have the same µ, (inductance) ?
Are you sure that all the magnets are the same and well matched (magnetic field)?
If the motor were not on the same shaft it would not be a problem, but it's not the case here.
But if you have chance it'll work fine.
Have a Nice Day.
Thierry
The thing is, I want to have up to 10kW output. So for 12S it would be around 220A, which is way too much for the VESC6 I guess (so one ESC for 2 motors is not an option). So in my opinion there are 2 options: either use 2 motors and 2 ESCs and split the power between both (and I think 110A are doable with the VESC 6 and watercooling) or to go up in voltage: with 24S (~90V) it will also be around 100A for 10kW.
I want to build an electric Surfboard, so the argument with 60V is still touchable and above it will be dangerous doesn't really count, since your skin resistance after 20min in saltwater drops significantly and even 40V will be dangerous. Sure 90V are more dangerous than 45V but I hope there will be sufficient insulation (IPX7). (the "DIN VDE 0100" states 12VDC as limit for underwater applications).
I know @antonchromjak and @Roger Wolff are working on a "high" voltage version of the VESC, but I don't know their progress so far.
Hi
Paltatech has done a high power version ( http://vesc-project.com/node/144 ) that works.
Have a Nice Day.
Thierry