AC 800M OPC Server Limitation

I have a redundant connectivity server connected to AC 800M controllers. I would like to know if this connection would be regarded as "One" or "Two" Opc server subscription ?

As per the limitation, a maximum of 3 opc server can be connected to a AC 800M controller.

My requirement is to have a connection by two redundant connectivity server and another two AC 800M OPC server to be installed in a separate PC's to serve data to third party client system. If this configuration is valid ?

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mohammed shama Rank: 276

Asked 3 years ago

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As far as I know, you need a separate license for each OPC server outside the one or two used to feed the 800xA system.

External subscribers can, if they like, subscribe via the OPC DA surrogate server available in all nodes belonging to an 800xA system, even though some overhead (security, etc) will apply then.

In your case, you need to order two (2) additional OPC server licenses.

I'm not sure the limit is only three...

I believe the limit is CPU load in the controllers. You can drive any AC 800M controller into CPU overload having just a single OPC server subscribing to it...

Make a good application (small tasks, with task offset in between each, sane amounts of inter-controller communication and not more than 50-55% cyclic load) and you can provide plenty of OPC data to several clients.

All boils down to CPU load and task tuning (cycle time, offset). Keep a watch on this and you can draw plenty of OPC data out of AC 800M controllers stretching from PM851 up to PM891 (the faster CPU, the more load it will carry, of course).

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by mohammed shama Rank: 276 on 2/28/2016 10:10:35 PM | Like (0) | Report

Dear Sir, We would not like to use the 800xA system OPC DA surrogate server as the third party client should be available even when 800xA system shuts down due to any reason. The limitation on the no. of OPC servers connected to the controller is given in the document 3BSE035983-510_en_AC_800M_5.1_OPC_Server.pdf.

by Stefan Stromqvist AKS expert

Rank: 1 on 2/28/2016 11:38:21 PM | Like (1) | Report

If you want to deviate from the documented maximum you should file a Temporary Sales Authorization request with your regional ABB sales representative.

With enough arguments, Product Management may issue an exception to the rule of max number of subscribing OPC servers.

A controller can have much more MMS connections than three, but three is the figure set as a limit - capacity must be reserved for other connections (process panels, intra-controller communication).

I can not issue any "carte blanche" here, but I'm certain more than three is possible if other parameters are adjusted in the other direction (e.g. no OPC AE subscription from the secondary OPC servers, less number of controllers, less number of subscribed items).

As I wrote first, it all boils down to CPU load and task tuning. With low CPU load and plenty of Task Offset in between task execution you can have more MMS communication.

by kstoilov AKS expert

Rank: 5 on 2/29/2016 1:47:46 PM | Like (0) | Report

We havetried with 2 OPC Servers: one redundant for 800xA and one for serving of third party OPC Client (Citrix). It is working good from a long time, for a total of 3 redundant pairs of AC800M. Like described in comment above, it depends on planning of available resources.

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Stefan Stromqvist AKS expert

Rank: 1

Answered 3 years ago

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AC 800M OPC Server Limitation

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