Controllogix and PowerFlex 70 VFD application

SilverLoop

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Join Date
Oct 2002
Posts
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i was wondering if anyone could get me started on an application i have involving a controllogix plc and powerflex 70 vfds (with encoders) on controlnet?

a sample programm showing how to send a start request with speed set point would be great. also, i am not sure how to get the encoder feedback from these drives.

thanks!
 
This is one of the things the ControlLogix does very well. PowerFlex 7-series drives with 20-COMM-C ControlNet adapters appear as I/O devices in the RSLogix 5000 controller organizer.

When you add a PowerFlex 70 (you are probably using the Enhanced Control "EC" version) to the I/O tree, controller-scope tags are created automatically with the names of their functions as sub-elements. The output tags for a PowerFlex 70 are:

Drive:O.Stop
Drive:O.Start
Drive:O.Jog
Drive:O.ClearFault
Drive:O.Forward
Drive:O.Reverse
Drive:O.LocalContrl
Drive:O.MOPInc
Drive:O.Accel1
Drive:O.Accel2
Drive:O.Decel1
Drive:O.Decel2
Drive:O.SpdRefID0
Drive:O.SpdRefID1
Drive:O.SpdRefID2
Drive:O.MOPDec
Drive:O.CommandedFreq

Followed by some UserDefinedData elements that are going to hold the parameters you point to with DataLinks. DataLinks are how you are going to get the encoder feedback data into your Logix controller.

Generally encoder feedback is used to enhance speed control accuracy.. don't presume that you're going to turn an AC drive into a position controller just because it has an encoder attached.

The PowerFlex 70 User Manual includes descriptions of how to configure DataLinks, as well as a good description on how to scale the Speed Command (in short, 0-32767 = MinFreq - MaxFreq, but there are some subtleties to the Maximum value).
 
Ken Roach said:
This is one of the things the ControlLogix does very well. PowerFlex 7-series drives with 20-COMM-C ControlNet adapters appear as I/O devices in the RSLogix 5000 controller organizer.

When you add a PowerFlex 70 (you are probably using the Enhanced Control "EC" version) to the I/O tree, controller-scope tags are created automatically with the names of their functions as sub-elements. The output tags for a PowerFlex 70 are:

Drive:O.Stop
Drive:O.Start
Drive:O.Jog
Drive:O.ClearFault
Drive:O.Forward
Drive:O.Reverse
Drive:O.LocalContrl
Drive:O.MOPInc
Drive:O.Accel1
Drive:O.Accel2
Drive:O.Decel1
Drive:O.Decel2
Drive:O.SpdRefID0
Drive:O.SpdRefID1
Drive:O.SpdRefID2
Drive:O.MOPDec
Drive:O.CommandedFreq

Followed by some UserDefinedData elements that are going to hold the parameters you point to with DataLinks. DataLinks are how you are going to get the encoder feedback data into your Logix controller.

Generally encoder feedback is used to enhance speed control accuracy.. don't presume that you're going to turn an AC drive into a position controller just because it has an encoder attached.

The PowerFlex 70 User Manual includes descriptions of how to configure DataLinks, as well as a good description on how to scale the Speed Command (in short, 0-32767 = MinFreq - MaxFreq, but there are some subtleties to the Maximum value).
Click to expand...

do you have to issue a Drive:0.Start command and a separate Drive:0.Forward command to start the motor in the forward direction? likewise, is it necessary to issue a Drive:0.Start command and Drive:0.Reverse command to get the motor to reverse?

sorry for the basic questions!
 
I have never done a pflex with clx but have with a slc and plc5 on RIO so I will assume it is similar.


If you configure the drive for unidirectional control (forward and reverse) you will have to send a command for direction along with a start command. You will also have to remove the stop command before issuing the start.

It is important to understand the difference between 2 and 3 wire control with these drives. I am not sure if it can be done over the network but with 2 wire hard wiring you send either a run forward or run reverse command and this command has to be held on as long as you want the drive to run. If you set up for three wire control you simply have to pulse the start command to start the drive and pulse the stop command when you want it to stop. (you have to remove the stop before issuing the start or no go)

Note that with a Pflex the stop command is "high" which is opposite of what most would think.
 
Directional control is done by settings one of the direction bits, for Forward or Reverse. Leave it set until you want to change direction. If neither bit is set, the drive will run in the last commanded direction, which is Forward if the drive has never been given a direction command since powerup.

The start bit in the Command word should be set high until the Running bit in the status word goes high.

Same thing for the Stop bit; set it high in the Command word and leave it high until the Running bit goes low.

The drive operates over the network like a "three-wire" configuration, except as noted that the Stop bit must be set high to stop, rather than being maintained high like a hardwired circuit.
 
Last edited:
Ken Roach said:
Directional control is done by settings one of the direction bits, for Forward or Reverse. Leave it set until you want to change direction. If neither bit is set, the drive will run in the last commanded direction, which is Forward if the drive has never been given a direction command since powerup.

The start bit in the Command word should be set high until the Running bit in the status word goes high.

Same thing for the Stop bit; set it high in the Command word and leave it high until the Running bit goes low.

The drive operates over the network like a "three-wire" configuration, except as noted that the Stop bit must be set high to stop, rather than being maintained high like a hardwired circuit.
Click to expand...

What happens if the direction bit is changed while the drive is running? I am assuming that it will ramp down and then change directions?

I have always told the drives I have worked on to "stop" before changing directions. Maybe this is not necessary? I would appreciate comments.
 
The PowerFlex over 22-COMM will simply reverse directions under those circumstances. It will ramp down & up using the Accel & Decel periods specified.

No need to issue the stop command.
 

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