AC motor driven electric bicycle control system

Thread Starter

zazas321

Joined Nov 29, 2015
432
Hey guys. I have got a task to design an AC motor driven electrical bicycle. Did any one of you had some experience with that? I had some ideas for example having the acceleration handle to change the frequency increasing or decreasing motor RPM. Which AC motor type is more suitable for the electric bicycle design?
 

crutschow

Joined Mar 14, 2008
23,502
You need an AC 3-phase motor specifically designed for vehicles.

Typically bicycles use an in-hub DC brushless motor for this task, such as these.
 

kjj

Joined Mar 30, 2018
31
Technically, a BLDC (brushless DC) motor is just a permanent magnet synchronous AC motor. So why not just buy a BLDC for electric bicycles? They are quite popular, you can find them on ebay, amazon, and dedicated shops.
 

MaxHeadRoom

Joined Jul 18, 2013
19,165
Technically, a BLDC (brushless DC) motor is just a permanent magnet synchronous AC motor. So why not just buy a BLDC for electric bicycles? They are quite popular, you can find them on ebay, amazon, and dedicated shops.
The subtle difference is that BLDC has only 2 windings under power at any given time, and the AC synchronous is true 3ph AC powered.
Max.
 

kjj

Joined Mar 30, 2018
31
The subtle difference is that BLDC has only 2 windings under power at any given time, and the AC synchronous is true 3ph AC powered.
Max.
That is just a matter of control. A BLDC can also be controlled with sinusoidal switching waveform. And AC synchronous can also use the simplest "BLDC" square wave control method, even though i don't think that is very popular. Remember that inverters for AC motors will always be close to this image: http://img.motors-biz.com/upload/tmp/1/d2982153cd46411b496d3add795d725b.PNG
 

MaxHeadRoom

Joined Jul 18, 2013
19,165
I realize that the motors are virtually identical, just that the term DC in BLDC is because it represents a DC motor turned inside out, as opposed to the 3ph AC version which could not be.
I have also worked with many Servo motors over the years and have also built picmicro BLDC controllers.
Max.
 

kjj

Joined Mar 30, 2018
31
I realize that the motors are virtually identical, just that the term DC in BLDC is because it represents a DC motor turned inside out, as opposed to the 3ph AC version which could not be.
I have also worked with many Servo motors over the years and have also built picmicro BLDC controllers.
Max.
No, a BLDC can be a "innrunner" or "outrunner", so i don't think that statement is true. From what i recall, the name BLDC comes from the fact that the motor+controller combination (many small BLDC have built in controllers) acts just like a brushed DC motor when seen from the + and - terminals. Lower DC voltage = lower steady state speed.
 

MaxHeadRoom

Joined Jul 18, 2013
19,165
I have always got the description from the motor manufacturers themselves, I am aware of out-runner, in-runner, but the term really describes the electronic equivalent of the mechanical commutation method of a brushed motor.
Max.
 

kjj

Joined Mar 30, 2018
31
The thing is that my task is to design an AC controller so im not entirely sure if the BLDC would do in my case
In any case, the general topology would be something like this: https://www.google.no/search?safe=off&biw=1920&bih=948&tbm=isch&sa=1&ei=Z0_QWq-rNcfYwQKlhK-IBA&q=ac+inverter+motor&oq=ac+inverter+motor&gs_l=psy-ab.3..0i8i30k1.699.1333.0.1450.6.6.0.0.0.0.93.460.6.6.0....0...1c.1.64.psy-ab..0.6.460...0i19k1.0.bVElhxz7AyI#imgrc=GULXzZmg_X2rUM:

The MOSFET selection/current rating will be based on the motor you choose. As for the code, microchip (and i guess Atmel) have some examples (just choose motor control): https://www.microchip.com/doclisting/CodeExamplesByFunc.aspx

Btw, what kind of "task" is this really? What is stopping you from buying off-the-shelf controller and motor?
 
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