Regenerative Braking

[Abhishek Singh]

Hello !!!!! This is Abhishek Singh working in electronics design segment as an application engineer. Currently i am working on BLDC motor control project. I want to lock the motor shaft whenever i need..Perhaps technical name Regenerative braking...someone told me that you have to make one control algorithm for regenerative braking...but i did not got exact idea. Is there any difference between only shaft locking and regenerative braking ????

Can any one explain me how exactly we can lock the motor... it will help me a lot....


Thanks;
Abhishek Singh

 

[BradtheRad]

If it were an ordinary DC motor then you could attach a low resistance to act as a load, and inhibit turning.

However if it's brushless then that won't work so easily.

You could short the coils when it is turning, in hopes that the coils going past the magnets will generate back-emf, and inhibit turning. But the current probably won't be sufficient.

Or you might apply current to the coils at the right time to attract the magnets. But that will consume power.

 

[chuckey]

To lock the rotor, just pas a lot of DC through the coils. This is current from a low source impedance.
Frank

 

[dick_freebird]

I think you want to use the control loop and command a
lower speed than rotor speed. You have to respect the
battery's charging current limitations and you want some
proportionality if this is a transportation application -
who brakes by locking them up?

If you can command negative torque, this is your best
regen braking I think. But you do want the energy to go
back to the battery instead of ground for regenerative,
so I think that wants a boost capability. Maybe some
BLDC drivers can operate that way but I would not
assume that of them all, especially the cheap ones.

Maybe simpler to attach a rectifier pack and a boost
converter, current-mode, than to try and retrofit the
function to an existing design.

 

[Abhishek Singh]

Thanks a lot for reply !!!!!!!!!
I am controlling BLDC motor with the half bridge.....can i off all the mosfets of half bridge except two of them (one from u phase upper and one from w pahse lower) so that mototr get locked. On two mosfets in PWM mode.

I really do not know whether it will work or not..

I want some more clear idea to lock the motor...please help me !!!!!!!!

Thanks;