Honeywell HPM, Service

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2 Equipment Description
2.18 Cabinet Fan Assembly
100 HPM High-Performance Process Manager Service R688
Honeywell December 2020
2.18 Cabinet Fan Assembly
Introduction
Fused 0.5 A 120 Vac or 240 Vac power is provided by the Power System for Cabinet Fan assembly
operation.
Up to four Cabinet Fan assemblies
Up to four Cabinet Fan assemblies can be powered by the 120 Vac or 240 Vac provided by the four 3-pin
connectors of the Standard or AC Only Power System configurations. The connectors and fuses are
located at the left side of the Standard Power System backpanel and at the bottom of the AC Only Power
System AC/DC Distribution assembly. See Figure 27, Figure 28, and Figure 29 respectively.
Optional Cabinet Fan assembly
An optional Cabinet Fan assembly has an LED indicator that indicates normal operation of both fans, and
an alarm signal, represented by normally open contacts, is available at a terminal strip, TB1. The contacts
are closed when the Cabinet Fan assembly is operating normally. The operation of the Cabinet Fan
assembly can be monitored by a 24 Vdc Digital Input FTA, by providing the alarm 24 Vdc signal source
from the FTA and returning it to the FTA through the alarm contacts.
2.19 LLAI Line Frequency Clock Voltage
Introduction
The Power System provides a nominal 6 Vac half-wave rectified phase reference signal to the
High-Performance Process Manager card file assemblies through the Power Distribution cable. A
pluggable solid-state optical coupler module, U1, on each type of card file backpanel generates this line
frequency phase reference signal. It is located at the bottom right of a 7-slot card file backpanel and in a
similar position on the 15 slot card file. Its 6 Vac output is routed to the Low Level Analog Input (LLAI)
IOPs through Power Distribution cables and card file backpanels. The signal is used by the IOPs to
improve the common and normal mode noise rejection ratio.
Standard Power System
In the Standard Power System configuration, the Power Supply Module located at the left side of the
assembly is the source of the line frequency phase reference signal. If the left Power Supply Module is
removed, the LLAI IOPs in the same cabinet will report a Soft failure and continue to operate, but at
lesser degree of accuracy.
AC Only Power System
The line frequency phase reference signal in the AC Only Power System configuration is not dependent
upon the presence of the left or right side Power Supply Modules, since a constant voltage is supplied by
the AC/DC Distribution Assembly.