AB 753 Buss Overvoltage

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ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
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EC - retired
200 HP irrigation pump motor.

We ordered a 753 set up with enclosure and all the goodies. It is configured as a 2 wire control and includes an HOA that uses a DI "Run" in Hand, and the same DI Run in the Auto via a N/O contact that we supplied. Auto also does a PI Enable via another DI.
Speed control is via a 0-10v pot when in Hand and a 4-20 ma in Auto.

We are getting a Fault Code 5 while in the Auto. I associate this with a short deceleration ramp time. We are supposed to be Coast to Stop, but I will have to confirm that is selected for both Modes. (Those making the changes have not given me a complete list.)

Baring that oops, would too tight of a PID loop cause this problem? We have a 3% deadband.
The motor does not seem to hunt for speed and sounds pretty quiet.

Note: The motor does run into the SF amps at 60 Hz and no doubt has ran there since installed some years ago.
 
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ptonsparky said:
200 HP irrigation pump motor.

We ordered a 753 set up with enclosure and all the goodies. It is configured as a 2 wire control and includes an HOA that uses a DI "Run" in Hand, and the same DI Run in the Auto via a N/O contact that we supplied. Auto also does a PI Enable via another DI.
Speed control is via a 0-10v pot when in Hand and a 4-20 ma in Auto.

We are getting a Fault Code 5 while in the Auto. I associate this with a short deceleration ramp time. We are supposed to be Coast to Stop, but I will have to confirm that is selected for both Modes. (Those making the changes have not given me a complete list.)

Baring that oops, would too tight of a PID loop cause this problem? We have a 3% deadband.
The motor does not seem to hunt for speed and sounds pretty quiet.

Note: The motor does run into the SF amps at 60 Hz and no doubt has ran there since installed some years ago.
Click to expand...
The combination of an overly aggressive Decel and a tight PI dead band can cause this, you're hunch is right. The tight dead and alone is likely OK, but there is no justification for having a short Decel on an irrigation pump that I can think of. Generally you want the Decel to be SLOWER than coasting if there is a check valve in the system, because you would want to avoid water hammer by allowing the kinetic energy in the moving water to dissipate slowly rather than turn into a shock wave (which is what water hammer is). coasting is OK for the PI control, but when you go to shut down, it may allow the flow to stop too fast. The way I like to do the setup is to not have the PI control on, then find the right length of Decel time that avoids water hammer. Once you have that, then turn on the PID loop. If there is no check valve in the system, then leave it at Coast to Stop.

By the way, most reputable motor mfrs will tell you that when run on a VFD, motors are never to be considered more than 1.0 SF. The pump OEMs sometimes don't care because they know the motor will likely outlast the one year warranty, but the end user suffers the consequences over time.
 
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Jraef said:
The combination of an overly aggressive Decel and a tight PI dead band can cause this, you're hunch is right. The tight dead and alone is likely OK, but there is no justification for having a short Decel on an irrigation pump that I can think of. Generally you want the Decel to be SLOWER than coasting if there is a check valve in the system, because you would want to avoid water hammer by allowing the kinetic energy in the moving water to dissipate slowly rather than turn into a shock wave (which is what water hammer is). coasting is OK for the PI control, but when you go to shut down, it may allow the flow to stop too fast. The way I like to do the setup is to not have the PI control on, then find the right length of Decel time that avoids water hammer. Once you have that, then turn on the PID loop. If there is no check valve in the system, then leave it at Coast to Stop.

By the way, most reputable motor mfrs will tell you that when run on a VFD, motors are never to be considered more than 1.0 SF. The pump OEMs sometimes don't care because they know the motor will likely outlast the one year warranty, but the end user suffers the consequences over time.
Click to expand...

If you don't have a check valve, you may have regen problem at stop, further accerberating the DCOV.
 
weressl said:
If you don't have a check valve, you may have regen problem at stop, further accerberating the DCOV.
Click to expand...
We had a check valve.

The faults all occurred while it was running at what I could tell, a very steady speed. Apparently we had selected the wrong Motor Control Mode. Induction SV vs Induction FV. FV allowed us to use an additional Autotune step that eventually led to a fault free operation.

My supplier provided setup assistance with the parameters. I knew, from past experience, some settings but no way all of them or how to make an Autotune work when it did not want to.

I can see the capabilities of this drive as I look through the 500 plus pages of the Programming Manual but sure do miss the simplicity of PowerFlex 4 quick start guide.
 
ptonsparky said:
We had a check valve.

The faults all occurred while it was running at what I could tell, a very steady speed. Apparently we had selected the wrong Motor Control Mode. Induction SV vs Induction FV. FV allowed us to use an additional Autotune step that eventually led to a fault free operation.

My supplier provided setup assistance with the parameters. I knew, from past experience, some settings but no way all of them or how to make an Autotune work when it did not want to.

I can see the capabilities of this drive as I look through the 500 plus pages of the Programming Manual but sure do miss the simplicity of PowerFlex 4 quick start guide.
Click to expand...

Once you get a set of parameters that work, save them and clone them for the next project.
 
ptonsparky said:
We had a check valve.

The faults all occurred while it was running at what I could tell, a very steady speed. Apparently we had selected the wrong Motor Control Mode. Induction SV vs Induction FV. FV allowed us to use an additional Autotune step that eventually led to a fault free operation.

My supplier provided setup assistance with the parameters. I knew, from past experience, some settings but no way all of them or how to make an Autotune work when it did not want to.

I can see the capabilities of this drive as I look through the 500 plus pages of the Programming Manual but sure do miss the simplicity of PowerFlex 4 quick start guide.
Click to expand...

Well you dealing with a specialized drive, the standard 550 drive has canned programs with quick startup modes. When you get into P&ID controls I doubt that the PF 4 is any simpler.
 
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