What are the risks involved in using same power supply for powering system and field in an AC800M HI based system?

As per the safety manual for AC800M HI (3BNP004865-511 Page 71), It is strongly recommended to use separate power supplies for powering System Units and powering Field Equipment. We have a requirement for supplying an AC800M HI based system with one cluster (2 DIs and 2DOs). And we have a space restriction to include separate power supplies for system and field. I would like to know the risks involved in using common power supplies for system and field. Also would like to know if anybody used this configuration in any of the project.

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anup.augustine Rank: 2392

Asked 8 years ago

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Hai,

Its not advisable to use same supply for PLC and Field IOs.A lot of things can go wrong in the field side, the most common cases are wires getting short with the ground, so when using same power supply, such circumstances may lead to PLC module failures.

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maanuaanu Rank: 637

Answered 8 years ago

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This topc can help you:

http://www402.abbext.com/SS823-Voting-unit-q10636.aspx

Generally 2 things influence proposed power supply for safety solution: SIL and availability.

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Radomir Pistek AKS expert

Rank: 47

Answered 8 years ago

Greeting

the most common risk for using one power supply for both the controller and the field devices , is to lose the controller supervisory in case of any malfunction occur in the field side which effect the stability of the power supply .

Normally you need your controller to be active in all time

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osama malhy AKS expert

Rank: 16

Answered 8 years ago

Hello,

Find here with reply from our sales support colleague,

"Separate power supply for system and field equipment is not required from safety (SIL) reason. However, we would like it to be separate for below reason (as documented in AC 800m controller Hardware manual

3BSE036351-510)