How to do programming for AC500eCo PM564 for RTD and VFD
I'm new to ABB plc. My client has PM564 PLC and he wants to use it for cooling tower application. so RTDs are used to sense temperature and fan(VFD) is used to vary its speed according to temperature.
I know only LD mode. Are there any examples with this type of configuration?
If not then guide me.
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I think Sumit has given you a link to the example program code in his comments.
The RTD's will required the correct type of IO Module as they cannot be connected to the On-Board IO of the PLC. You should be able to adjust the VFD Reference Speed using one of the On Board Analog Output channels or an Analog IO module.
This is really quite a simple program. You need to use one PID controller to controll the motor speed depending on the temperature measurement and setpoint. Connect the output of the temperature PID to the Drive Speed Reference Output channel. ( Do not make the mistake of trying to use a "speed Controller" - this is built into the VFD ) A program like this is really only 3 or 4 function blocks ... Input Scaling -> PID -> Output Scaling
This is an "analog" application, so really, LD is a bad choice of programming language. CFD or FBD is quite easy to learn and your program will be MUCH easier to write and commission if you use one of these languges.
If you are completely new to AC500, there are some good introduction videos on Youtube ... https://www.youtube.com/watch?v=Q6zBX...
"Should I control VFD(ACS355) via Modbus or via Analog output?"
That depends on how much data you want to pass between the VFD and the PLC and / or the HMI.
If you have no HMI, then a simple analog speed output will be enough.You will probably also want 2 digital inputs from the drive to tell you that the drive is "Ready" ie no fault, and "Running" ie speed > 0.
If you want more information - eg fault codes, motror currents etc, then a Modbus or Profibus link will be required. Again, programming a modbus link using LD will be very difficult and you should use CFC or FBD for this. ( I think perhaps the example code for these links will be in ST )