Control.com - Nerds in Control

Hello to all,

I don't have much experience with ABB's equipment, and I'd like to know more about AC800M controller, especially if it can have redundant CPUs on one controller board. Is that possible?

I want to have a solution that will provide full redundancy, so I need two redundant Ethernet networks with two communication modules.

Should I need also two AC800M controllers in order to have full redundancy?

Thank you very much.

Hi Mike,

Yes its possible to have redundant AC800M. You have to ask for model PM861 or PM864 that has this capability through two processors. They also can work in single mode. The AC800M has by itself a redundant ethernet port.

Maybe you can get more information about AC800M through http://www.abb.com or looking for support in the local ABB.

Best Regards,
Jose

From what I remember of the AC800M you can have redundancy for both controllers, network, power and I/O. The design is up to you really. The installations I have seen have had redundant networks as a minimum.

Chris Jennings

Thank you for your replies.

I'm trying to get as much information (from different sources) as possible. I heard that these controllers are significantly cheaper than S7-400 and can be economically better solution comparing to S7 400H PLCs from Siemens, when redundant solution is preferred. However, it's a little strange to me that actually one controller with two redundant CPU is used. I think two separate PLCs are better solution, because AC800M must have some form of backplane bus in order CPUs and I/Os to communicate, so in case of some kind of fault, both CPUs could go down, which is not exactly 100% solution. Am I right here?

For full redundancy, you will have to go in for two separate controllers.

The problem with these ABB controllers is that the changeover time between the controllers is so long(> 5 seconds)that it defeats the very purpose of redundancy.

Hello,
I'm very interested in this. Can you provide more informations, or direct me where I can find it.
Is that time of 5 sec with controller with two CPUs or in general?

I know that there must be some kind of backplane bus which is used for communication between CPUs and I/Os. If that fails, everything fails.
Maybe I should ugo with two separate controllers....

Hello,

Where are you getting your data from >5sec
I do not think so.

Hi,

Had some experience with the AC800M series. Very cost competitive. We bought 1 system for process plant in China before where the temperature is below 0 deg C. Had some problem with the fibre optic cables that connect to extended IO carrier where those extended IOs were not able to detect by CPU. At the end, needed to use a hair blower to heat the system... haha... even with heater installed in the PLC panel, this problem still persists.

Yes, you should go for 2 separate controllers.

Now, let us take the case that you have these 2 separate controllers and they are working in redundant operation. One controller is active and the other controller is in hot standby mode.If the active controller fails, the standby controller should quickly take over from it. The trouble with ABB controllers is that that the time is more than 5 seconds for this takeover to happen. In the intervening time, the process is badly affected and often the whole plant stops leading to loss of production. Therefore, I suggest that in case you are keen for proper redundancy, look for another system.

PVRN,

That is very strange to me. Is that from your own experience?

I have found on the following datasheet that switch over time is about 10ms.

Very strange indeed.

Do you know any official data you can direct me to, so I can use this as an argument why not to use this controller?

PVRN,

Sorry, I hate saying that someone is wrong, but the general statement that all ABB AC800M redundant controllers take 5 seconds to switch over to backup is simply not true.

If you have experienced a problem where your controller is stopped for 5 seconds during a fail over, then you have a serious issue that should be addressed by ABB support line.

http://www[.]lymac.co.nz

Sorry, but I also hate to say that truth is bitter. AC800M has major problems with redundancy. It does not work properly.

Talking about ABB's support service, it is very bad. ABB takes very long to respond and charges high amounts for service.

Sorry, but I also hate to say that truth is bitter. AC800M has major problems with redundancy. It does not work properly.
Talking about ABB's support service, it is very bad. ABB takes very long to respond and charges high amounts for service.

As for the redundancy changeover, I too find that very hard to believe. There must be something wrong with either the hardware installation or software setup. ABB DCS and PLC systems are generally very fast in changeover. So much so that the SCADA does not even know a changeover took place

PVRN, please can you describe me your solution? I want to make sure same thing cannot happen to me.
If you can, please send at mik_alvis at yahoo.com

Thanks