regenrative braking capabilities of MID-7652

[mihonyc]

Hello

I'm doing preliminary research on the following project concerned with the reel-to-reel web handling system.  The system should consist of a pay off reel (unwinder), tension sensor and a take up reel (winder). Both reels should be directly driven by DC brush servo motors controlled through PCI-7342 and MID-7652. During the transport of the web in the forward direction the web is pulled by winder motor and tensioned by the unwinder motor (based on the feedback from the tension sensor). (And vice versa when the web is transported in the backward direction). As I understand the unwinder motor acting as a brake actually generates the current, which flows into the drive (MID-7652). It's called regenerative braking or negative torque (current) or four quadrant operation of the drive (in contrast to single quadrant operation - positive positive speed/torque only and two quadrant operation - positive speed/torque and negative speed/torque only). If the drive allows for the regenerative braking (negative torque or current) it should contain the circuitry to either return the generated current into the power supply bus (which is unusual for AC powered drives) or shunt it inside of the drive. I went through the documentation related to MID-7652 which I could find but did not get any clues on whether or not it can be used in such a way.

Could you please comment on using NI motion controllers and drives in "braking mode" (i.e. when the controlled motor should provide some negative torque)?

Thank you very much in advance!

Michael

[Jochen · Accepted solution]

Hello Michael,

if you use the MID-7652 in quadrant 2 and 4, the absorbed energy loads a capacitor of the 48 V power supply. In normal operation modes this is not a problem, as bringing a motor to a stop does only generate a small amount of power, that can be easily be handled by the capacitor. If you need to run the motor for a longer time in quadrant 2 or 4, the drive has to disapate the energy with one of the methods that you have described in your post, but this is not possible with the MID-7652.

With this said, the MID-7652 is probably not a good fit for your application and you should use a 3rd party drive in combination with an UMI. 

I hope that helps,

Jochen Klier

National Instruments

[mihonyc]

Dear Jochen,

thank you very much for your comprehensive answer!

I'll be looking into 3rd party drives that allow for continuous operation in quadrant 2 and 4.

With best regards,

Michael

Message Edited by lockia on 08-05-2009 09:50 AM