Electrical Engineering - Questions on Allen-Bradley PowerFlex 700S (VFDs) and ControlNet

Author

Questions on Allen-Bradley PowerFlex 700S (VFDs) and ControlNet

Iconoclast

2007-05-11, 8:25 pm

I'm working on an application in which the customer will have a ControlLogix
PLC, and we plant to use ControlNet to interface with some Variable
Frequency Drives and in so doing, reduce the number of PLC I/O points that
would otherwise be hard-wired to conventional PLC I/O modules (in this case,
1756-IA16Is and -OA16Is, if memory serves me right.) I am specifying an A-B
1203-CN1 communications module to be put in the VSD's compartment. (BTW, the
1203-CN1 has 2 coaxial cable ports and an Ethernet port; coaxial cable is
the default way to communicate using ControlNet. The 1203-CN1 also has a
9-pin, I think, male connector for a mating cable which runs to the drive.)

I have some questions:

- This drive has a Bypass mode in which it can run as a full-speed motor.
I'm trying to figure what it would take to allow the 1203-CN1 module to pick
up this input. We'll have a 3-position AFD-Off-Bypass switch on the drive's
compartment; maybe the ControlNet link could somehow be used to monitor the
Bypass position. Does anyone know how something like this work, or how the
"Drive in Bypass" signal could be communicated to the 1203-CN1 module?

- We will bring 1 to 3 other inputs into the drive's compartment from the
field that are unrelated to the drive's internal workings (e.g., a high
temp. alarm from a non Allen-Bradley device.) There be a relay for each with
dry contacts in the drive compartment. Does anyone know if a dry contact
representing any status signal can be picked up and communicated to
ControlNet somehow?

I'd love it if anyone could give answers they're darned confident about.

Mike

SVOsprey@gmail.com

2007-05-21, 5:25 pm

The 1203-CN1 is for drives that use SCANPort interfaces, which today
would mostly be the 1336 Plus II drives. It has Channel A and B
connectors for ControlNet, and a ControlNet Network Access Port (it's
RJ45 but its not Ethernet, it's a ControlNet N.A.P.).

One of the limitations of the network interface is that it doesn't
have extra I/O points to bring in related I/O points that don't
connect to the drive.

I/O that does connect to the drive can be set to not have any effect
on the drive, but could be read back over a DataLink connection over
ControlNet.

The DeviceNet SCANport interface had a special version called the 2100-
GK61 that has four extra Inputs onboard. There's no similar
ControlNet/SCANport interface with extra I/O.

There's a more modern Drives Peripheral Interface (DPI) box for
ControlNet that has some onboard I/O. If you are using a PowerFlex
drive, this is the way to go:

http://www.ab.com/drives/20-comm/20-xcomm/index.html

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