# How does a brushless DC motor controller have regen?



## Technologic (Jul 20, 2008)

I'm curious how the:
http://www.kellycontroller.com/shop/?mod=product&cat_id=26,15&product_id=430

type of regen works electronically. Does the regen switch the polarity of the coil to the reverse of the timing used to power it? Switch the coil inside to a DC magnet?

Thanks


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## 3dplane (Feb 27, 2008)

Hi!
While I'm not an electronic expert I know that a BLDC controller does not have to do anything for regen except to provide a path for the power to go.What I mean is that the motor just turning IS a generator (alternator)
without any excitation. I'm pretty sure that it must use a clever configuration of diodes and other related components,but no effort needed to make the motor produce power as long as it is turning,(due to the permanent magnets) (now to exceed the pack voltage to achieve charging is a different story)
Barna


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## Technologic (Jul 20, 2008)

3dplane said:


> Hi!
> While I'm not an electronic expert I know that a BLDC controller does not have to do anything for regen except to provide a path for the power to go.What I mean is that the motor just turning IS a generator (alternator)
> without any excitation. I'm pretty sure that it must use a clever configuration of diodes and other related components,but no effort needed to make the motor produce power as long as it is turning,(due to the permanent magnets) (now to exceed the pack voltage to achieve charging is a different story)
> Barna


a simple low voltage recitification circuit could up the voltage to something useable... though the info on kelly's page about regen and how it works is non-existant


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## samborambo (Aug 27, 2008)

Brushless DC motors, as well as all permanent magnet motors, are self-exciting. The output is not unlike 3 phase AC reticulation. If you want to build a standalone generator, simply connecting 6 diodes arranged in a "six pack" as a three phase rectifier will give you a DC output. The load into which you want to dump energy into needs to be controlled in order to do anything useful - eg: you would need a buck/boost controller between the rectifier and the batteries to control how much regen is applied.

A BLDC controller usually handles regen by outputting a voltage phase lag to what the motor is spinning at. This is known as V/F (voltage/frequency) control and the voltage of the waveform is scaled proportionately to the speed.

Alternatively, the latest tech is space-vector control. Based on the position of the rotor (and therefore the phase angle) the BLDC controller computes on the fly the advance or retard of the voltage waveform in order to apply a negative or positive torque on the motor.

Space vector control is a bit more processor intensive but gives the best efficiency and tighter control of the motor.

Microchip have some good application notes on V/F and SVC. They don't mention regen and the applications are aimed at indutrial speed control, not automotive torque control. Fairly trivial to adapt though.


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## 144VDC (Jan 25, 2009)

The research I have done so far tells me it is the back 
emf that provides regen; if the motor rpm is high enough it will charge the batteries through diodes. But to work when the bemf is below the battery voltage, you need switches in place of the diodes to create a boost regulator. The motor winding is the inductor and pwm of the switch will boost the bemf up to the battery voltage.
Jerry


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## Technologic (Jul 20, 2008)

samborambo said:


> Brushless DC motors, as well as all permanent magnet motors, are self-exciting. The output is not unlike 3 phase AC reticulation. If you want to build a standalone generator, simply connecting 6 diodes arranged in a "six pack" as a three phase rectifier will give you a DC output. The load into which you want to dump energy into needs to be controlled in order to do anything useful - eg: you would need a buck/boost controller between the rectifier and the batteries to control how much regen is applied.
> 
> A BLDC controller usually handles regen by outputting a voltage phase lag to what the motor is spinning at. This is known as V/F (voltage/frequency) control and the voltage of the waveform is scaled proportionately to the speed.
> 
> ...


Thanks for this explanation, almost all of it made sense


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## samborambo (Aug 27, 2008)

144VDC said:


> The research I have done so far tells me it is the back
> emf that provides regen; if the motor rpm is high enough it will charge the batteries through diodes. But to work when the bemf is below the battery voltage, you need switches in place of the diodes to create a boost regulator. The motor winding is the inductor and pwm of the switch will boost the bemf up to the battery voltage.
> Jerry


Jerry, that's correct - and probably a bit easier for others to understand. Well put


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## brdriver (May 26, 2009)

You are my techer on BLDC motor control!
all one say he is willing to use AC solution,i am not agree the ideas.maybe they really didn't know what is BLDC excellent special characteristic.hehe...
your said is very good,hope you keep chat some of basic knowledage on here.
let's make friend with bldc solution!
best regards!

waiting for your response.my Msn:[email protected]



samborambo said:


> Brushless DC motors, as well as all permanent magnet motors, are self-exciting. The output is not unlike 3 phase AC reticulation. If you want to build a standalone generator, simply connecting 6 diodes arranged in a "six pack" as a three phase rectifier will give you a DC output. The load into which you want to dump energy into needs to be controlled in order to do anything useful - eg: you would need a buck/boost controller between the rectifier and the batteries to control how much regen is applied.
> 
> A BLDC controller usually handles regen by outputting a voltage phase lag to what the motor is spinning at. This is known as V/F (voltage/frequency) control and the voltage of the waveform is scaled proportionately to the speed.
> 
> ...


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