The WEG CFW500 Drive has three different PID implementations.
The first one is part of the drive’s native parameter set. It’s your basic PID implementation
that allows the drive to automatically adjust the motor’s speed to maintain whatever process
you are monitoring. Typically, temperature, pressure or flow – stuff like that.
The second PID implementation is referred to as the “Internal PID.” It does everything
the native PID does except It’s an application that you load into the drive’s built-in
PLC. It also adds the ability to use a second analog input to bias the feedback result as a sum,
difference or average. And it has low and high-level alarms. You can use this one or
the drive’s native PID, you can’t use both because they both want to control the
same motor. The third PID implementation is referred to
as the “External PID” and it is also an application you load into the drive’s built-in
PLC. Instead of controlling the drive’s output to the motor, it controls an Analog
output which you can then use to control some other external actuator just like you would
with any PLC or controller. So this is just a generic PLC-based PID that you can use for
whatever you want and you can use it while running the drive’s built-in PID. Which
means you can have the drive controlling a motor and the built-in PLC controlling another
process. Which saves you the cost of having to buy separate PLC to control that other
process! Here’s the plan: This video is just a quick
overview. We’ll then take a few minutes to understand
and characterize the hardware we’ll be using in this series. That’s always the first
and most important step when implementing PID. You need to make sure you understand
what your hardware is capable of and how it performs, so don’t skip that one.
Next, we’ll show you how to set up the parameters and how to use the drive’s native PID. And
I’ll show you the trick I use to massively simplify and track all the PID related
parameters. Then we’ll show you how to use the Internal
PID implementation. It’s pretty much the same thing except you have to load the PID
application into the built-in PLC first and it uses different parameter numbers and has
a couple extra options. The external PID implementation uses the
exact steps and doesn’t really have anything to do with the drive’s motor control so
I’m going to skip that one for now. Maybe I’ll do a video on that guy if enough folks
ask for it in the comments below the video. Finally, we’ll do a sleep mode example which
is great for applications where you want PID to automatically fill a tank to some level,
but then go to sleep until the tank drains down to some lower level where PID wakes up
and automatically fills the tank again. That way the drive isn’t burning power trying
to automatically maintain a tank level. One side note: We did a whole series of videos
that did similar quick starts for the WEG CFW100 and CFW300 drives AND then also broke
up the whole PID algorithm up into small bite sized chunks where you can learn all about
the Setpoint options, tuning a PID loop, noise reduction techniques, how to use bumpless
modes, pretty much every aspect of using PID. While those all use the WEG CFW300 drive,
the same concepts apply here too. The only thing to be aware of is those smaller drives
only have the PLC version of PID, they don’t have the native drive parameter version that
the CFW500 has and the CFW500 PID will typically have more options. But the concepts are the
same and will definitely get you close enough. In this WEG CFW500 series, we’re just going
to focus on getting you up and running quickly with these videos.
Ready? Join me in the next video where we learn about the hardware we will be using.
Again, understanding your hardware is the most important step to successfully implementing
PID. Meanwhile, click here to learn more about
the WEG CFW500 Variable Frequency Drives. Click here to learn about AutomationDirect’s
free award-winning support options and click here to subscribe to our YouTube channel so
you will be notified when we publish more videos like this one.