SLC 5/04 and Powerflex Drives

Hey Guys,

I am still new to this, but I am trying to get a grip on this one. I could use some input to figure this one out.

I have a SLC 5/04 Processor, and I am going to be adding, 14 Power-flex 4 Drives to the system. What would be the best way to integrate this into my program? Would device net work or control net? Again, I'm new to the Power-flex end of the program.

I tried to figure it out, but it got me all confused. Any advice and input is greatly appreciated.

Thanks

Devicenet (1747-SDN card) if you need access to the drive's parameters beyond just start/stop, speed reference, and a return fault signal that the h/w i/o provides.

The 20-COMM-R can provide a Remote I/O connection (1747-SN card) but I haven't used it and am not sure to what level of signals it provides; certainly more than h/w but probably less than DeviceNEt.

(PS: make sure when choosing a powerflex family that you check out the communication options; some have fewer than others)

I would shy away from ControlNet. It is more powerful and faster than Devicenet, but less common.

If you use devicenet, you'll need RSNetworx for Devicenet software. If you use the devicenet interface, be sure you follow all the proper power supply and network cabling recommendations.

You can't use RIO, which is unfortunate since it is so easy and cheap to set up, but they don't offer a RIO interface for the PF4.

The other obvious choice would be to simply hardwire them.

Before you decide, you need to know what kind of control you need. Mainly, are you going to be varying the speed and direction, if so how frequently?

EDIT: It looks like the PF4 would require a connection to a PF40 or a 22-XCOMM-DC-BASE, since it does not directly support a built in comms network. You can connect four PF4's per PF40 or 22-XCOMM...

If I were you, I would lean toward hardwired control with DC output cards for direction commands, and analog for speed commands...The other advantage to doing it that way, is that any brand and model of drive will support that type of control.

Unfortunately, the Powerflex 4/40/400 Series do not support Remote I/O. The 20-COMM-R is for the Powerflex 70/700/7000 Series.

As Okie pointed out, the PF4 VFDs do not support anything but DPI. You need to go to a PF40 or above, and need a different cover to hold the Comm Card. You can use a PF40 with a Comm Card, and 4 PF4 Drives Daisy Chained on DPI. The 22-XCOMM-DCBASE will support 5 Drives, and you need to populate it with the Comm Card of your choice.

DeviceNet is a good choice, and we have several system using it. In most circumstances, I find using Comm Cards cheaper than I/O, and more versatile. However, with the PF4 limitation in this setup, the advantage isn't quite as great.

It has been my experience that using Comm Cards is usually about 1/2 the price of using I/O, but your mileage may vary.

Stu.....

Because these are PowerFlex 4 drives, you are limited to Modbus RTU over RS-485 wiring, or using an external communication module like the 22-XCOMM-D.

There is a lot of "it depends" in the answer, based on how fast you need the drives to respond to start/stop and speed change commands, and how much data you intend to poll from the drives.

You could do something as simple as attaching a 1761-NET-AIC to the serial port of the SLC-5/04 controller and using the Modbus RTU master function of the serial port to send MSG instructions to start/stop/speed control the drives.

The next level of sophistication would be to use a Prosoft MVI46-MCM module to manage the Modbus RTU messaging to the PowerFlex drives. In my experience this is a lot faster and easier to commission because you don't have to manage all the MSG instruction code, just a configuration of the Prosoft module, which will handle retries and timeouts and message timing onboard.

If the drives need fast control, discrete On/Off and Analog speed command is the only way to go. If they're running fans and pumps and other relatively slow-reacting devices, you can do the start/stop functionality over the network.

Remember that these are the lowest-end drives that Allen-Bradley makes, and you're connecting them to a popular but aging SLC-500 controller, so they're not going to have the kind of performance you'd see from PowerFlex 7-series on Ethernet with ControlLogix.

I am a big DeviceNet proponent, but in this application it might be overkill.

Post more about your application; this Forum has a lot of users who have probably commissioned automated systems with similar requirements and can share their experiences.

The only reason why we chose the powerflex 4 drives is due to major space restrictions. The only place they will fit is the MCC center.

Our application is for a refrigeration system using energy management. We are adding space temp sensors to each zone. We will be using a PID control loop to vary the process speed on the coil. I would prefer to use communication as this is an old system we would be upgrading with absolutely no room at all.

Also, would it be easy to communicate via 485? and how would I do this?

Also, A dumb question, but it has to be asked, Since I am putting these in a MCC center, What the general rule for cooling?

Has anyone gone the prosoft module route? I would like to know more about this. This seems to be the best option for what I have available.

king,
It has been my experience that the Power Flex 4 model of drives don't particularly like to be in a closed up space without proper cooling. Several of the ones we have used ended up dying an early death. AB salesman blames the failures on cooling anyway. They are small & cheap but they cant take a cramped up hot cabinet.

General rule for cooling a PF4: keep the cabinet temperature below 105F, while following the spacing rules in the owners manual. If the cabinet gets to 110F better shut it down or the drives will start failing no matter how well spaced they are.

I have never used the RS485 myself. I have seen a setup where one drive has DeviceNet & then several more drives were slaves off of the PF4 comm port. I didn't like it because it is a nightmare to replace one of the slave drives without proper documentation (node number). Documentation always seems to impossible to locate when needed.

BD

Is it possible to mount the drives near the motors? If so you could use PF70's and 20comm-R (RIO) This way you wouldn't have to cram the VFD's into a cabinet and you might not need to use filters or line reactors to prevent the drives from faulting due to any long runs.
This is pretty common but I'm not sure how much vision you can get from VFD to HMI
Have fun though!