2 BLDC motors 1 controller..?

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Faz
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2 BLDC motors 1 controller..?

Post by Faz » Mon, 01 Aug 2011, 18:58

The question is, can two BLDC motors be controlled with one (suitably rated) controller?
I wouldn't expect proper operation with sensorless controllers but if two motors are rigidly connected, phased correctly and used with a hall sensor would it work?

I would expect yes but please give me feedback on the pros and cons.

Thanks.

Tritium_James
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2 BLDC motors 1 controller..?

Post by Tritium_James » Mon, 01 Aug 2011, 19:40

If they're rigidly connected then they're effectively one motor as far as the controller is concerned. Halls or sensorless operation should be possible.

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jonescg
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2 BLDC motors 1 controller..?

Post by jonescg » Mon, 01 Aug 2011, 20:19

I assume this means the phase wires would be wired in parallel?
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Faz
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2 BLDC motors 1 controller..?

Post by Faz » Mon, 01 Aug 2011, 20:39

jonescg wrote: I assume this means the phase wires would be wired in parallel?

That was my thinking.


Assuming the motors are of the same type but not specifically matched in inductance or impedance. ie: two from the same factory but with no effort made to select closely matched motors.
Is there any side effects or possible problems to parallel-ing two brushless motors?

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2 BLDC motors 1 controller..?

Post by Tritium_James » Mon, 01 Aug 2011, 23:41

You'd be able to wire them in parallel or in series, either would work, it would depend on which was the best match for the current & voltage ratings of the controller. If they're fairly close to each other in their various parameters I wouldn't expect any problems running like this.

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jonescg
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2 BLDC motors 1 controller..?

Post by jonescg » Tue, 02 Aug 2011, 00:50

Well from my experience running two brushed DC motors in parallel is difficult, especially when they might not be perfectly matched. I burned out two motors at Eastern Creek because if this unmatched dilemma.

I have conversed with Roman Sunsik from EMRAX motors, and he indicated that while two of his motors may be run from one controller, it was not recommended:


"Hi Chris,
We do not recomended one controller for two motors. But we can say that it works if boath of motors has totaly the same temperature inside (on the cooper windings).
If the temperatures are different the resistants are different - so the motor which has lower temperature can get higher current - and this is not good...Also we do not tested yet. It could be the same story as you used to get from Agni motors.
Motors can be assembly on the same shaft and you rum them separately with two controller (Sevcon or Unitek are good solution) - Unitek weight app 6kg.

Water cooled ,motor is a litle bit more efficient (get more continuous power) compared with aircooled which need air speed app 90km/h. So we recomender water cooled. Perhapes we will tested LC EMRAX totaly enclothes (with out any cooling holes) in August/September. We will see.

Piktronik controller is one of the best and it have been tested much more than others. But LC SAC41 weight 12kg. The price is 3890 euros + displey and HV modul.
Best regards   Roman"

Series was not recommended either:
"Better is with two separate controllers.
We are planning also to make a electric car with two motors on one shaft put them on the diferencial. We will make also the tests with one controller / two motors. Than will see...
Serial is too complicated - the first motor must have different ends of windings to connect in to the second motor...."

Make of that what you will Image
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2 BLDC motors 1 controller..?

Post by Tritium_James » Tue, 02 Aug 2011, 14:07

We routinely use either a series or parallel connection on the Ultramotive Carbon motor, which has two sets of windings internally. But I guess in that case they're closely thermally coupled, so the mismatch doesn't show up.

I didn't even consider the 'burning out a motor' case, as our controller monitors winding temperature, so it's not possible to burn out a motor. If you used a controller that didn't do this, then I wouldn't recommend driving two motors with one controller either.

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2 BLDC motors 1 controller..?

Post by Faz » Tue, 02 Aug 2011, 17:02

Thanks for the replies guys.
Tritium I'm having a problem getting my head around the diagram for running two three phase BLDC's in series? Image
Can this be done with both delta and star motors?

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woody
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2 BLDC motors 1 controller..?

Post by woody » Tue, 02 Aug 2011, 17:44

In series, you run each phase in series.
In parallel, you run each phase in parallel.

You need to have independent access to each end of each phase, I.E. 6 wires from each motor.

Image

If you have each phase on motor one called U1-U2 V1-V2 W1-W2 and on motor two U5-U6 V5-V6 W5-W6, then you wire them like the diagrams on the right.

cheers,
Woody
Last edited by woody on Tue, 02 Aug 2011, 07:47, edited 1 time in total.
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Faz
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2 BLDC motors 1 controller..?

Post by Faz » Tue, 02 Aug 2011, 18:58

woody wrote:
You need to have independent access to each end of each phase, I.E. 6 wires from each motor.


And that's why I couldn't get my head around the layout. As any BLDC motor I've seen is only three wire.

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2 BLDC motors 1 controller..?

Post by Richo » Wed, 03 Aug 2011, 20:38

plettenberg predator has 6 wires.
still may not be good enough for a good bike conversion tho
So the short answer is NO but the long answer is YES.
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Faz
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2 BLDC motors 1 controller..?

Post by Faz » Wed, 03 Aug 2011, 21:05

Thanks Rich. I'm actually thinking about a car conversion.
I've got my eye on a Honda city on ebay. Was thinking about two ME0913's. If they can reach the claimed peak of 30kW each I reckon it would be a good little ev.

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2 BLDC motors 1 controller..?

Post by aegidius » Sat, 08 Oct 2011, 15:53

The ME0913 is itself two motors in parallel, isn't it?
Giles.

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