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Old April 15th, 2019, 08:02 PM   #1
Steve Bailey
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Frenic (Fuji) Mega drive

Anybody have any experience with the Frenic Mega VFD's PID feature?

Today I was trying to modify a customer's setup with less than spectacular results. The drive is controlling a fan and has been functioning OK for several months under control of its own PID with the setpoint coming from the drive's keypad. The control loop is modulating the frequency reference to achieve a current setpoint.
The customer wants to be able to establish the setpoints from the HMI in the control room rather than from the drive keypad. They also want to operate in a additional mode where they enter a speed setpoint instead of a current setpoint. They have an unsuccessful attempt to achieve the second mode of operation. Their attempt was a selector switch wired to two of the drive's discrete inputs. One of those inputs was programmed to be a preset speed selection, the other programmed with a value corresponding to something called "Cancel PID Control". For those who know the drive the parameter was E06 which controls the interpretation of the signal on the X6 terminal and the value of the parameter is 20.
The "Cancel PID Control" command does not do what they expected it to do. It appears to still be reacting to an unstable PID loop. Instead of operating at the preset speed it will slowly ramp down to around 10 Hz (the preset setpoint is 25 Hz) and then jump up to 60 Hz and ramp down again.

The manual seems to indicate that asserting this command should disable the PID controller and permit preset speed control, but experience is otherwise. Does anyone know if the "Cancel PID Control" was added at a specific firmware level?

To get it to work the way they want I had to change the value in parameter J0 which enables/disables the PID function. That parameter can't be changed while the drive is running nor does the customer have the means to change it from the control room.
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Old April 15th, 2019, 08:49 PM   #2
sparkie
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This seems silly, but it may be the case. If they are just giving an input to disable the PID, it *could* be that the drive wants to see the signal lost before it switches modes. I've seen this before, such as drives not restarting until they have went low and then high.

Next, when changing terminal assignments, those drives must be power cycled. I couldn't find it in the mega manual, but I'm pretty sure I had to cycle power when changing terminal assignments when I set a couple of these up.

Next, F02 is the operation method. Make sure that the default method is set to get a reference from the appropriate position. These drives have a ludicrous amount of features on them and can be set up to do anything you want. It took me a few hours, a notebook, and a manual just to do a simple setup.

Perhaps H18 would also be of use, this is for Control target. Page 5-126 has a couple small truth tables to deal with the (possible) inverse IO settings.

6-13&6-15 has a block diagram of the control logic.

Finally, 7-11 has some specific information for the setup you are trying to accomplish.
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Old April 16th, 2019, 06:48 AM   #3
lesmar96
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Quote:
Originally Posted by Steve Bailey View Post
The customer wants to be able to establish the setpoints from the HMI in the control room rather than from the drive keypad. They also want to operate in a additional mode where they enter a speed setpoint instead of a current setpoint.
So under the new mode of operation they want it to run a constant speed? Am I correct?

Quote:
Originally Posted by sparkie View Post
Next, when changing terminal assignments, those drives must be power cycled. I couldn't find it in the mega manual, but I'm pretty sure I had to cycle power when changing terminal assignments when I set a couple of
I have not had any experience with this...........

The multi-frequency settings (C05-C15) will override anything, including the PID control, even without "cancel PID loop" true. I don't have experience with using that feature, but in several PID setups I have done, it ran on a PID loop with the setpoint commanded from the drive keypad, but under a certain condition we wanted to run at 60hz. That signal was wired to X1 (X1 defaults to SS1) so we programmed C05 to 60.0. and that has worked fine.

Not sure if this will solve your issue or not.
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