isengineer

Mitsubishi A700 VFD torque control by RSV (Load Sharing)

6 posts in this topic

Hi All, 

I was wondering if any of you guys could help me about improving my load sharing application. At the moment it's very unstable and i can't see what i am doing wrong! Thanks. 

Details:

I am trying to run a industrial chain conveyor using Torque control by Real sensorless vector control function of A700 Mitsubishi VFD. I have been following "Technical Note" which is provided by mitsubishi (see attached PDF). 

As described on technical note, i am trying to control 5 motors ( 1 X 2.2kW, 4 X 1.1kW) to share the load on this chain conveyor. Torque command (SV) and Motor Torque (PV) read from Master VFD and PID output (MV) of Q03UDE transferred to Slave VFDs over CC-link.

i would appreciate any information and help you can provide,

Many Thanks. 

Application_Technical_Note_Load_Sharing.pdf

Share this post


Link to post
Share on other sites

Not positive I can help but can take a look. I have a little experience with this. 

Are you able to post your projects PLC and VFD?

More details on the problem you are experiencing as well. 

Share this post


Link to post
Share on other sites

So, I am not able to find a problem here. Hopefully someone else can help.

isengineer, if you see this and do not mind doing so post the symptoms you had sent to me that may give a better idea of where to look for others. 

Good luck

Share this post


Link to post
Share on other sites

Symptoms are,

  • On run signal all drives accelerating up to set frequency (30Hz) fine (i believe during acceleration and deceleration, torque control not exercised)  
  • Then master drive runs at 30Hz and slave drives continues to increase their speed. I know that this is happening because MV (which is my torque command for slave drives) is quite large. Maybe i need to adjust my PID parameters to make it less responsive!
  • But what i don't understand, all 4 slave drives not running at same speed, even though same MV value driving them all! Because of this some section of the chain conveyor stretches and some sections bunched up. 
  • Ideally i need all drives to run at same speed ( apart from Sinew drive, because this one has a larger diameter drive wheel and it needs to run 0.96 times slower than the others) so i can keep line tension same on everywhere on the line but i need all 5 drives to share the load.

Thanks.

Share this post


Link to post
Share on other sites

A bit late.

I must admit I haven't tried the load-sharing function before, but I've ran torque controls. Do you also set the maximum speed limit for all drives (e.g. speed should never exceed master drive + e.g. 2%)? Unless you set a maximum speed limit, all drives will continue to increase speed "unlimited" until their torque is applied correctly.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now