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Description / Abstract:
The requirements in this Outline are to be used as a supplement
to the requirements located within IEC 61204-7: Low Voltage Power
Supplies, D.C. Output – Part 7, Annex PS-E.
Referenced within IEC 61204-7 is the third edition of the
Standard for Safety of Information Technology Equipment, UL
60950/CSA C22.2 No. 60950-00. Therefore, the numbering scheme of
the clauses and subclauses located in this Outline correspond to
those found in UL 60950/CSA C22.2 No. 60950-00. The requirements of
UL 60950/CSA C22.2 No. 60950-00 are applicable with the exceptions
noted in the Outline as ²replacements², ²additions², and
²deletions².
The requirements from IEC 61204-7: Low Voltage Power Supplies,
D.C. Output – Part 7, Annex PS-E, shall apply where details are not
specifically provided in this Outline.
Where a particular subclause of IEC 61204-7 and UL 60950/CSA
C22.2 No. 60950-00 is not mentioned in this outline, that subclause
shall apply. The relevant requirement, test specification, or note
in UL 60950/CSA C22.2 No. 60950-00 should be adapted accordingly
where this Outline states"addition," "modification," or
"replacement,".
The block diagram in Figure 1A displays, in single line form, a
typical d.c. power distribution system. The rectifiers provide the
power for the telecommunications load equipment and maintain the
charge (float) in the batteries. The batteries and/or the backup
generator provide the energy when interruption of commercial a.c.
power occurs. The d.c. distribution system is to provide energy to
the telecommunications load equipment with minimal power losses
regardless of the state of commercial a.c. power. The d.c. power
distribution system transmits the energy from the rectifiers or
batteries to the telecommunications load equipment. Overcurrent
protection devices may be provided within the distribution among
the rectifier outputs, batteries, or the input to the primary
distribution system. The rigid bus bar, which is typically used, is
designed for a minimum voltage drop and is a distribution structure
capable of withstanding fault currents.
The distribution system may be divided into the primary and
secondary distribution. The primary distribution system contains
the overcurrent protection devices, the wire, and cable to connect
the output voltage from the batteries and rectifiers to the
secondary distribution system. The overcurrent protection devices
provide the fault and isolation protection when a short or overload
condition occurs on the wire or cable between the primary and
secondary distribution systems. The secondary distribution system
contains the overcurrent protection devices (such as fuses and
circuit breakers), the wire, and cable to connect the output
voltage from the rectifiers and the primary distribution system to
the telecommunications load equipment. The overcurrent protection
devices in the secondary distribution system are intended to
protect the wire and cable from faults in the secondary
distribution system. Equipment faults are normally protected by
overcurrent protection devices either within the telecommunications
load equipment of the frames, which contain the telecommunications
load equipment, or within the D.C. SECONDARY DISTRIBUTION
circuit.