BLDC motors mechanically coupled

Joined
Nov 24, 2019
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Hello fellow users, its me again.

I was talking with a friend about electric motors and their applications for transportation (small EV conversions and such), and he brought the idea of using multiple small BLDC motors coupled/welded together in a single mechanical shaft to move, instead of choosing a single bigger motor.

The idea seemed interestng at that moment and i told him that i was gonna check some materials and contect on the internet about this, and for induction motors like the HPEVS lineup (AC34X2), and series wound motors (like a lot of drag racing machines and other EV conversions, being locked in a single shaft or connected indirectly by gearboxes or chains), but i can't find much information about it with BLDC motors, if it's okay to do it or if its gonna break something, or in a minute or in a year. But i have found a video where the guy uses two motors physically connected and two separate controllers to move a car, like my friend told me.

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In this video, the guy simply connect both motors together and wire them with their sensors to the separate controllers, but one of the motors gets two phases shifted, but i couldn't tell if it was because he connected the second motor back-to-back with the first or if he knew something i still need to learn.

I hope someone here can help me with that. No specific motor model was chosen, his only idea was to have 2 or more BLDC motors mechanically coupled, most certainly sensored motors to be sure of the correct working under load.
 
There are no problems mechanically connecting two BLDC together that I can think of as long as they have their own controller. They are working closed loop, meaning the influence of one motor isn't going to disturb the other one and they are still going to contribute to torque production. Problems start to occur if some would want to connect two motors paralleled on one controller only. In that case a small misalignment of the stator and rotor regarding to the other would cause unbalance and recicrculating current causing drag and inefficiencies.
 
Thecoco974 said:
There are no problems mechanically connecting two BLDC together that I can think of as long as they have their own controller. They are working closed loop, meaning the influence of one motor isn't going to disturb the other one and they are still going to contribute to torque production. Problems start to occur if some would want to connect two motors paralleled on one controller only. In that case a small misalignment of the stator and rotor regarding to the other would cause unbalance and recicrculating current causing drag and inefficiencies.

Each motor will have their own hall sensors and own controller, the thing that made me a bit worried is if they aren't in the exact same eRPM, so maybe one stator could try to pull and/or push the other
 
Check out any VESC based controller. They can connect to each other over a CAN bus and operate multiple motors in sync. the electric skateboard builders do it all the time. eRPM between the two motors are kept within a tight difference.
 
shaman said:
Check out any VESC based controller. They can connect to each other over a CAN bus and operate multiple motors in sync. the electric skateboard builders do it all the time. eRPM between the two motors are kept within a tight difference.

I was checking the VESCs, since they can be cheap to test in smaller scales (80-130$ a dual vesc)
But since i tried to find more things about it, seems that i can physically lock them in the same shaft but still having independent controllers for each stator
 
If the two coupled motor are driven from two separate controler in torque mode each can be driven independantly with different torque command and still contribute (each torque adding UP) .If you are driving them in speed control they need to have the same speed command. Torque command is a must have for me but it might work with speed control to.

Envoyé de mon Redmi Note 9S en utilisant Tapatalk

 
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