Specifications

RN: 5-93
RS3: Software Release Notes for P1 R4.2
Changes to RS3 Manuals
Case 1: Two power supply modules on Bus A require the same source
capacity used on Bus B; therefore, Bus B must be protected
for the same loading (86 amperes) as Bus A. It does not
matter how many over-current devices (for multiple sources)
are used as long as the input to Bus B is protected for a
maximum load of 86 amperes. Simply stated, the concept is:
make the Bus B loading and over -current protection
equivalent to Bus A.
Case 2: Three power supply modules on Bus A require equivalent
sources on Bus B that have over-current protection for a total
load of not more than 129 amperes. T his concept is the same
as in Case 1.
Case 3: Four power supply modules on Bus A require equivalent
sources on Bus B that have over-current protection for a total
load of not more than 172 amperes. Again, this concept is the
same as in Case 1.
Bus B Power Provided by the Factory:
When F isher-Rosemount supplies all System Power Supply Units for
buses A and B, the same number of power supply modules are on both
buses. F our power supply modules (two full System Power Supply
Units) on each bus is the maximum load allowed in the redundant bus
configuration (see Figure 1.2.8). See “Redundant Bus/Redundant
Power Supply Configuration” below for more information on adding
power supplies to each bus for additional redundancy.
Redundant Bus/Redundant Power Supply Configuration
Each bus (A and B) requires a separate redundant power supply
module in redundant bus/redundant power supply configurations (see
Figure 1.2.8A). Therefore, each bus requires a minimum of two power
supply modules and a maximum of five power supply modules. (This
would be a redundant bus/redundant power supply configuration with
N+1 redundancy.) Maximum bus loading requires four planned power
supply modules to supply the load plus one additional module as a
redundant module for that bus. Each bus must be configured as such.
This provides extra redundancy and permits a maximum of 172
amperes DC loading. To ensure safe operation, this load and number of
power supplies on each bus must not be exceeded.
This is a legitimate configuration but is inefficient in the use of power
supplies. This configuration is likely to be used for applications where
extra redundancy is required. One of the two previously described
configurations will normally be more desirable to use.