Hi,

If an encoder is use to regulate the speed of a motor with a vector drive instead of controlling
it in the open loop mode, does the affect the deceleration.

I mean, can we get faster deceleration?

 

I would say you should be able to get a more precise - more controlled deceleration... not necessarily faster... you could set the output of an open-loop drive to 0V-0Hz and it will try to stop as fast as it can.

The problem you may have is dissipating the energy that is regenerated. If it is doing this stopping starting all day, these days you will want to find a way to recycle that energy through a regen or active front end unit, DC bus load sharing, etc. If it only does it once a blue moon (i.e. e-stop condition) then a db resistor would be fine.

Follow the manufacturer's guidelines.

 

Short Answer: Yes, probably.


Long Answer:
It depends a lot on the controller/drive. As I recall, vector drives monitor motor current & voltage and are able to make decisions off of them, meaning that there may be some degree of closed loop control to it already.

What you are really looking for is whether or not the drive has four quadrant control. This refers to the ability of the drive to actively control deceleration. The four quadrants being Forward Acceleration, Forward Deceleration, Reverse Acceleration, and Reverse Deceleration.

Two quadrant control only allows for direction control and acceleration, but may switch in a resistor to dump the regen current. Four quadrant drives actually apply a braking signal to the motor on deceleration.

In general, the use of an encoder or other feedback device to close the control loop should give you more precise control, but whether or not it gives you more control that you currently have will depend a lot on your application.

Jim Miller
Application Engineer
Quantum Devices Inc
www.quantumdev.com

 

Concerning drive speed regulation, I have documents on the control equations for velocity servo speed regulation. These documents are available to email. If interested contact me.

Regards,

George Younkin, P.E.

gwyounkin at charter. net