vfd speed control

Since ou are not sure how to do the simple part of this task, that of matching the input resistance, then it is unlikely that you are qualified to handle the more important part of it, that of implementing a PID control loop to accomplish what you are asking.

Buy yourself two Allen Bradley SMC Flex starters, and have Rockwell come set them up for you...

Hello Guest,

You might want to look into some sort of summing input card. With it you could take your speed pot and sum ( usually can be add or subtract by way of signal inversion) it with your current feedback to get a "corrected" speed reference which would be fed into your inverter. Good Luck!

Shawn

First of all the E540 has PID functions built in. Page 151 of the manual discusses the development of PID control http://www.meau.com/Files/IB_NA_66866-H.PDF.

You would use a 4- 20ma signal for the feedback reference. (the one from your other motor) and the 0-5 / 0-10 reference for the set point setting. This is where you would use your POT. Re the converter. Phoenix Contacts has several good converters. I have had good luck with these in the past.

BTW the Misu E540 drive is a very good Sensor-less vector drive. no need at all for the AB unit. I have used these or one of there predecessors for years. One was on a stacker following a offset Press via tach generator.

I know that the Mitsi drive has PID. My point was that if he is having trouble with the simplistic issue of resistance, the PID tuning is going to be near impossible for him. He needs to get someone involved who knows what is involved. Too often I have to deal with people who, after listening to some salesman, believe that projects like this are simple enough for the average person to accomplish, when in fact they are not.

JRaef, You are correct that PID tuning / setup can be a complex issue for an inexperienced process person. But we don't know his / her background. I have had many an Engineer work for me that could program / design process controls that did not know a thing about input impedance. I have had to do many simple electronics / theory classes. This does not reflect badly on the Engineer but it does reflect badly on the School he / she came from. Now back to the issue at hand, at least this guest realized he / she needed to look at impedance matching here, many would not have seen the issue. Now to "Guest", if you have an issue with programming the Mitsubishi Drive, don't worry, many have trouble with it's complex programming set, call the distributor you got the drive from. They may either have an on-staff Applications Engineer or an Integrator that could walk you through the process. You might also see if an Integrator / Consultant could give you, "sell" you, a few hours of training on how to set up and tune the Mitsu for PID functions (your distributor should be able to provide you with a list of Integrators). Load balancing with a Sensor-less Vector drive is not as common as with Servo systems but it is still common enough that many integrators / Application Engineers can help.

Thankyou BCT and others for taking the time to answer my question.