cheap e-Bike controller modified for EV AC Motor

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cts_casemod
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cheap e-Bike controller modified for EV AC Motor

Post by cts_casemod » Wed, 21 Nov 2012, 15:36

Hello guys,

For simplicity reasons I've come out with the idea to drive my AirCon and Power steering pump using the car alternator, so I can keep the same brackets and belt setup.

I am using an e-bike brushless controller and I have been doing some tests to be able to run the thing without the field wire as this is an extra thing to worry about.

The controller is a syncronous type, so obviously will not run the alternator unless the field is powered.

So, what I did was to use the encoder input to trick the controller and force it to output a frequency higher than the alternator speed, which did actually work. I was able to measure 1Amp excited on the field coil, by an ampmeter shorting the brushes. I am limited as I am not using feedback at the moment.

Since I was thinking to change the power mosfets to run on a higher voltage (Currently 36V) I was thinking to get some proper drivers and run some IGBTs with it.

The toque (slip) and speed(frequency) could be controlled using a microcontroller to advance slip and frequency in regards to the motor actual speed, either from an encoder (For LS operation) or from a speed sensor (for HS operation).

Since this brushless controllers are really cheap I was wondering what do you guys think of the idea. Much less hassle that working with a VFD and the output stage can be built to specific needs.

Last edited by cts_casemod on Wed, 21 Nov 2012, 04:42, edited 1 time in total.

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jonescg
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cheap e-Bike controller modified for EV AC Motor

Post by jonescg » Wed, 21 Nov 2012, 18:33

Sounds like a good idea to me!
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Johny
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cheap e-Bike controller modified for EV AC Motor

Post by Johny » Wed, 21 Nov 2012, 19:10

If you are planning on using an unmodified car alternator you will have to supply field current via the brushes or any current you put into the stator will not result in any meaningful rotation.
If you use an RC ESC that does not use hall sensors (uses back EMF to sense rotor position) to power the stator, then you may get a reasonable motor that runs OK at a fairly fixed RPM - but you must engergise the field.

These guys have discussed this a lot - don't follow any links as they lead to nowhere useful.
http://www.motoredbikes.com/showthread. ... -As-Motors

cts_casemod
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cheap e-Bike controller modified for EV AC Motor

Post by cts_casemod » Thu, 22 Nov 2012, 01:56

Johny wrote: If you are planning on using an unmodified car alternator you will have to supply field current via the brushes or any current you put into the stator will not result in any meaningful rotation.
If you use an RC ESC that does not use hall sensors (uses back EMF to sense rotor position) to power the stator, then you may get a reasonable motor that runs OK at a fairly fixed RPM - but you must engergise the field.

These guys have discussed this a lot - don't follow any links as they lead to nowhere useful.
http://www.motoredbikes.com/showthread. ... -As-Motors


Johny, I believe you are a bit confused with my topic,

I am using the alternator as a motor already, using a brushless controller.

I have done a small test some months ago, before the start of my conversion, to be able to use it as a start and stop system as well.

What I have to report now is that I have been able to run the alternator as an induction motor. For this I have used the hall sensors input and provided the controller with a frequency, that in turn powered the alternator with a 3 phase current with the rotor stopped and and created a current on the rotor... Well you know the theory.

I was able to measure 1Amp induced on the rotor, but I know this thing can withstand up to 4.

What I need now is to implemet a circuit with a microcontroller to read the motor speed and an imput from a potentiometer to calculate the output speed/torque.

Now the goal/main point is to use the brushless controller as cheap interface between our circuit and the power module to run a standard AC motor.

I am not good at programming so if someone wants to give it a go let me know and I will post further details on this.
Last edited by cts_casemod on Wed, 21 Nov 2012, 15:03, edited 1 time in total.

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Johny
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cheap e-Bike controller modified for EV AC Motor

Post by Johny » Thu, 22 Nov 2012, 18:54

cts_casemod wrote:For simplicity reasons I've come out with the idea to drive my AirCon and Power steering pump using the car alternator, so I can keep the same brackets and belt setup.
No, I understand what you are doing and that you have run the alternator as a motor by inducing current in the rotor. What I was saying is that it will be pretty gutless unless you power the field in the rotor. The rotor was not designed to be induced. Sure it rotates and that's fine.

Anyway, since it will be running auxilliaries, it follows that you can run it in speed mode provided it has enough torque to maintain sync. So you could simply ramp the AltMotor up to speed over say 2 to 5 seconds without regard to actual speed just by ramping the input to the controller. You could have dual inputs so that aircon demanded optimum full speed and if aircon not running, steering could be inverse vehicle speed sensitive.
Or just run it all the time. Either way, I can't see that you need torque control.

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cheap e-Bike controller modified for EV AC Motor

Post by Richo » Thu, 22 Nov 2012, 20:53

My concern is the Power steering and aircon will require more than the usual 1kW peak output from an alternator.
You may need 5-10kW peak. ~2kW cont

So the short answer is NO but the long answer is YES.
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