Sidactor Protection Thyristor Products Page 61 SIDACtor Protection Thyristor Products

SIDACtor Protection Thyristors 2017 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 02/23/17 Overvoltages from TELECOMMUNICATION NETWORKS possible? Normal operating voltages Within SELV CIRCUIT limits Exceeding SELV CIRCUIT limits but within TNV CIRCUIT limits Yes TNV-1CIRCUIT TNV-3 CIRCUIT No SELV CIRCUIT TNV-2 CIRCUIT To ensure safe operating conditions of equipment, UL 60950-1 focuses on the insulation rating of the circuit(s) under consideration. Tables 3.50 and 3.51 (next page) indicate the required creepage and clearance distances depending on material group, pollution degree, working voltage and maximum transient voltage in the secondary circuit. For a typical telecommunication application with a working voltage of 200 V, pollution degree 2, material group IIIb, the creepage distance is 2 mm. In this example, the clearance distance would be 1.8 mm if the transients are limited to values less than 800 V but allowed to go higher than 71 V (and no special quality control program is in place). This clearance distance is intended to prevent arcing during overvoltage events. IF the minimum creepage distance derived from these tables is less than the applicable minimum clearance distance, then that clearance distance would be used. The highest transient voltage in a TNV-1 or TNV-3 circuit is determined by applying a 10x700 S voltage waveshape surge event with an open circuit value of 1.5 kV and a 5x310 current waveshape with a short circuit value of 37.5A. For a TNV-2 circuit, this highest transient voltage is determined by applying a 10x700 S voltage waveshape surge event with an open circuit value of 800 V and a 5x310 current waveshape with a short circuit value of 20A. These surges are applied 3 to 6 times in each polarity with a minimum of one second between impulses across: 1) the positive and negative supply points 2) between all supply points joined together and protective earth 3) between tip and ring and 4) then between tip and ring joined together and earth. Table 3.49 TNV Levels UL 60950-1 Terminology (continued) When determining the working voltage for TNV-2 & 3, it is assumed to be 120V dc unless it is specifically known for the application. For a TNV, it is assumed to be 60V dc, unless it is specifically known for the application. Telephone ringing signals are NOT taken into account for this determination. A coated PCB may use the smaller separation distances as provided in the table below IF its manufacturing process is subjected to a quality control program that assures double insulation and reinforced insulation compliance. PEAK WORKING VOLTAGE X V peak FUNCTIONAL, BASIC or SUPPLEMENTARY INSTALATION mm REINFORCED INSULATION mm 90 0.1 0.2 180 0.2 0.4 230 0.3 0.6 285 0.4 0.8 355 0.6 1.2 455 0.8 1.6 570 1.0 2.0 710 1.3 2.6 895 1.8 3.6 Table 3.52 Regulatory Requirements (continued)

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