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Forum Index : EV's : brushless motor doubling as generator

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Ninja Chris

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Joined: 26/04/2011
Location: New Zealand
Posts: 2

Posted: 06:24pm 30 Dec 2015

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Hello all, not a frequent visitor here but I thought this might be the appropriate place to ask this question: Does anyone know of an off-the-shelf solution for controlling a brushless motor that can also handle generation when that motor is driven?

My question relates to Bryan Roberts' gyromill concept and the practicalities of turning a quadrocopter into one by replacing the fixed propellors with variable pitch ones like this. The motor/generation control system seems to be the major technical challenge to overcome here.

Thanks,
NC

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 04:04pm 31 Dec 2015

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Tough one. Dont know of anything off the shelf.

You could connect a 3 phase bridge rectifier across the motor terminals, and it should not affect the motor controller when the "device" is running as a motor, provided the bridge rectifier output is open circuit. When you want to run the device as a alternator, you can connect a load to the rectifier output, and that will work, but the motor controller may has a hissy fit, depending on how smart/dumb it is.

If the motor controller can be disabled, so its drive signals to the power mosfets are all off, then it should be OK.

Glenn

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Ninja Chris

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Joined: 26/04/2011
Location: New Zealand
Posts: 2

Posted: 10:44pm 31 Dec 2015

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Hi Glenn, thanks for the reply. I've been thinking about this some more and had a bit of a revelation: I think the functionality I desire is identical to the regenerative braking that is built-in to e-bike brushless motor controllers. This seems to be well described here.

Edit: Also found cheap, simple, regenerative brushed motor drivers: https://www.dimensionengineering.com/datasheets/SyRen10-25.pdf

Further edit: There's a useful discussion of regenerative braking in e-bike controllers here. The short version is that some do offer this function but that it is not particularly efficient or well handled. The function I desire, where power is fed back into the battery from a brushless motor operating as a generator in an optimised manner, is termed "variable regenerative braking" and is not yet available on off-the-shelf units. It does seem to be close, though. Edited by Ninja Chris 2016-01-02

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