Hello, I am working on a project involving use of TTL frequency counter to measure motor speed, as feedback to the VFD. The VFD will be monitored/ controlled by a PLC.

Please suggest what I should start studying specifically about this interface and what all topics should I cover.

I am fairly new to this. Thanks.

 

VFD - Vacuum Fluorescent Display, is it right?
TTL frequency counter - using TTL logic ic to design the frequency counter?
as feedback to the VFD - is this meant to display on VFD?
So you involved with TTL ic, VFD driver, PLC?

 

VFD= Variable frequency 3ph motor drive?
What make of VFD is it, or has it not been decided?
Some have a configurable output for indicating different functions, but the current/rpm status is usually analogue.
There is also PLC's with 0-10v analogue control output to the VFD and a encoder input card for rpm.
But I am guessing you would like to do it the simplest way?
Max.

 

VFD= Variable frequency 3ph motor drive?

Oh, yes, this is more reasonable.

 

I install Allen-Bradley VFD for a living. They have little display that shows the frequency. I don't see the point of this exercise.

 

I install Allen-Bradley VFD for a living. They have little display that shows the frequency. I don't see the point of this exercise.

It would appear the OP wants to monitor RPM in order to control it with the PLC?
Max.

 

It would appear the OP wants to monitor RPM in order to control it with the PLC?
Max.

Maybe.
A-B VFD have ethernet port. Some setups we would have multiple VFD run to hub/switch and then from hub/switch connect to PLC. Other times we daisy chain the VFD using ethernet cables and then connect one VFD to the PLC. This is all A-B stuff. Kinda explains why A-B is so expansive, they do put money into making their product have all kinds of options.

 

This is all A-B stuff. Kinda explains why A-B is so expansive, they do put money into making their product have all kinds of options.

There are others also that offer option expansions, Mitsubishi for just one.
Max.

 

I'm working on my Master thesis work. The project involves connecting a Variable-frequency drive to a PLC system via EtherCAT which will in turn control a 3-phase induction motor.

The VFD is a WEG-make CFW11 series with a EtherCAT module installed
Motor is a 3-phase 110kW WEG-make Synchronous motor

I want to use the TTL signal from the motor speed encoder as one of the inputs to the VFD, and finally control the VFD via the PLC platform via EtherCAT. The PLC platform (SW and HW) I'm using has been indigenously developed by my company. I already have the VFD's xml file which describes its interface and functioning.

Has anybody had experience with installing similar setup? Any technical points which are to be kept in mind?
Eventually I will have help from other tech guys at the company, but I want to be as prepared as possible.

Thanks.

 

I want to use the TTL signal from the motor speed encoder as one of the inputs to the VFD, and finally control the VFD via the PLC platform via EtherCAT. The PLC platform (SW and HW) I'm using has been indigenously developed by my company. I already have the VFD's xml file which describes its interface and functioning.

I don't follow.

The VFD determines the sped of the motor so how is the speed of the motor going to determine the settings of the VFD without creating an unstable feedback loop?

If it's for motor slip compensation that's easily factored in and adjusted for with one or more settings in the VFD's own software and programing setup rendering external feedback loops unnecessary.

None of what you are saying makes any sense to me being as others have already said there are far simpler ways to handle things than your approach.

Encoder to PLC to VFD would be the extent of the external contorl loop setup n my views and all of that should be near plug and play setup with most any modern components regarding each device. especially so if they are already factory built with ethernet network connection compatibility.

 

What I would do, and have done in the past, for accurately controlling the RPM of a VFD run motor is instead of using a sensorless vector VFD, buy the VFD with the encoder option and input the encoder back to the VFD.
If you are using a network communication for input control then generally you can specify the frequency direct and in conjunction with the VFD encoder obtain very close control.
This also should alleviate the problems that may arise tuning a feedback loop via a PLC.
This is if you are not locked into to a specific solution.
Max.