Basic VFD/motor troubleshooting: no torque

[The Plc Kid]

I have and what they cost for what you get sucks IMO. I think Dick DV was making reference to a drive worth having ABB, Rockwell or Siemens.

 

[DickDV]

Well put, jraef and PLC Kid!

 

[Cow]

I'm going to push hard to get a temporary starter and 460V AC hookup to test the motor, and order a new drive in the meantime, while backing up the drive parameters by hand.

Sometimes when I'm troubleshooting a questionable drive, I'll pull the motor leads off the load side of the drive and install them under the same terminals as the line side wiring. Use the breaker as an on/off switch. I usually only do this for test purposes on smaller motors although we did run a 100HP directly off a breaker once waiting for some drive parts to come in.

 

[Eddie Willers]

Guys, thanks for all the troubleshooting tips and general advice.

There are two of these machines that were built to identical prints by two different OEMs (long story) and because there have been no technically-capable people touching them for years I concluded that the problem could not be a configuration problem.

I stepped through all 80-something parameters on both AC drives on the keypad and looked up the meaning of each one.

And sure enough, somebody had been messing with the one that didn't work, and it might have been back in 2012. They customized the V/Hz ratio and put in "custom boost" values that evidently were just enough to get the big carousel moving under ideal conditions.

When just a little more static friction developed, those boost levels wouldn't let the motor move at all.

I changed all the parameters to match the parameters in the drive that was running correctly, and what do you know... lots more starting torque !

These machines move very slowly; the "slow" speed was 2 Hz and the "fast" speed was 5 Hz. Maybe next time they'll put in an appropriate gearbox.

Again, thanks for all the troubleshooting pointers. Sometimes the most important part of troubleshooting is eliminating the things that aren't wrong.

 

[allscott]

Guys, thanks for all the troubleshooting tips and general advice.

There are two of these machines that were built to identical prints by two different OEMs (long story) and because there have been no technically-capable people touching them for years I concluded that the problem could not be a configuration problem.

I stepped through all 80-something parameters on both AC drives on the keypad and looked up the meaning of each one.

And sure enough, somebody had been messing with the one that didn't work, and it might have been back in 2012. They customized the V/Hz ratio and put in "custom boost" values that evidently were just enough to get the big carousel moving under ideal conditions.

When just a little more static friction developed, those boost levels wouldn't let the motor move at all.

I changed all the parameters to match the parameters in the drive that was running correctly, and what do you know... lots more starting torque !

These machines move very slowly; the "slow" speed was 2 Hz and the "fast" speed was 5 Hz. Maybe next time they'll put in an appropriate gearbox.

Again, thanks for all the troubleshooting pointers. Sometimes the most important part of troubleshooting is eliminating the things that aren't wrong.

Or at least put in a vector drive. I'm not surprised you are having trouble running open loop V/HZ at those speeds.

 

[Eddie Willers]

A proper vector drive, along with a direct-acting brake and a new HMI are among the proposals I've made for the system.

My real Catch-22 is that if I improve this underperforming system then I'm likely to get underbid for the next one too.

Thanks for your comments !