FAQ - Redundant FISCO -
FAQ - Redundant FISCO
| Q |
Is the change-over ‘bumpless’ ? |
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| A | Yes. Interruption of fieldbus communications is momentary, and is accommodated by the re-transmission mechanism that is implicit in the Foundation fieldbus protocol. There will therefore be no loss of control, and the plant operator will observe no loss of data. |
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| Q |
What’s inside the ‘Supply Arbitration Modules’ ? Are there relays inside? |
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| A | Each Supply Arbitration Module (SAM) contains electronic circuits to monitor the output of one FISCO power supply, and to switch the output of that power supply to the field segment. The switching is solid-state, so there are no relays. The two modules communicate with each other by ‘handshaking’ to make sure that they can never both be ‘on’ at the same time. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Q |
Will the output specification of Redundant FISCO be the same as the existing 912x-IS power supplies? |
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| A | There will be a slight reduction in available output current and voltage compared with MTL’s existing range of ‘simplex’ power supplies, but this will result only in a small change to the maximum segment length or device loading. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Q |
Why are there two Supply Arbitration Modules per fieldbus segment? |
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| A | To eliminates single points of failure for complete redundancy. If one ‘SAM’ fails, the system continues to provide power to the fieldbus segment. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Q |
Does the Redundant FISCO power supply work with existing Intrinsically Safe Megablock wiring hubs, or do they need to be different? |
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| A | Redundant FISCO works with MTL’s existing range of IS Megablocks (types F245 – F271). | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Q |
Can the modules be ‘hot-swapped’ to allow replacement of failed modules without losing power or communications? |
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| A | Yes. The power supply and Supply Arbitration Modules may be easily ‘hot swapped’ without powering down the system, and without causing loss of power or communications. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Q |
Can the existing 932x-SC Spur Connectors be used to connect to ‘Entity’ certified fieldbus devices, and devices in Zone 0 hazardous areas? |
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| A | Yes, these can be used on Redundant FISCO segment in exactly the same way as for simplex. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Q |
Doesn’t the FISCO standard say that there should be only one source of power in a FISCO network, making it impossible to have redundant power supplies? |
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| A | No. This clause in the IEC60079-27 standard is intended to mean that the maximum values of Uo, Io and Po for the power supply must not be exceeded on any segment, and that the power must be connected at only one point on the bus. MTL’s solution complies with both these requirements because it provides power onto the segment at only one point (at the power supply terminals), and the Uo, Io and Po values for the redundant output will be certified to comply with the maximum values specified for FISCO. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Q |
What cable lengths can be supported using Redundant FISCO |
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| A |
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