UL SUBJECT 1801

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 &#8211; Part 7, Annex PS-E. <br>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 &#178;replacements&#178;, &#178;additions&#178;, and &#178;deletions&#178;. <br>The requirements from IEC 61204-7: Low Voltage Power Supplies, D.C. Output &#8211; Part 7, Annex PS-E, shall apply where details are not specifically provided in this Outline. <br>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,". <br>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. <br>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.