Sidactor Protection Thyristor Products Page 54 SIDACtor Protection Thyristor Products

SIDACtor Protection Thyristors 2017 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 02/23/17 UL 497 Series of Safety Standards The UL 497 series is a family of three safety standards that provides requirements for protection devices used in low- voltage circuits. UL 497 addresses requirements for primary protectors used in paired communications circuits. UL 497A covers secondary protectors for use in single or multiple pair-type communications circuits. UL 497B addresses protectors used in data communication and fire alarm circuits. UL 497C addresses protectors for coaxial circuits. UL 497D addresses protectors located on the equipment side of a primary protector, also known as the protected side of the circuit (typically current activated devices such as TBUs.) The focus of UL 497 is to ensure that paired communication circuit protectors do not become a fire or safety hazard. The requirements in UL 497 cover any protector that is designed for paired communications circuits and is employed in accordance with Article 800 of the National Electric Code. The protectors covered in UL 497 include solid state primary and station protectors. These circuit protectors are intended to protect equipment, wiring, and service personnel against the effects of excessive voltage potential and currents in the telephone lines caused by lightning, power fault, power induction, and rises in Ground potential. UL 497 Construction and Performance Requirements The "Construction" section covers the following requirements: General Enclosures Components Spacing Protection Against Corrosion Field-wiring Connections The "Performance" section covers the following requirements: General Line Fuse Test Instrument Fuse Test Arrester Test Polymeric Material Test Rubber Materials Test Jarring Test Water Spray Test Drop Test Cover Replacement Test Strain Relief Test Marking Corrosion Test, Outdoor Use Protector Replacement Arresters Installation Test Appliqu Assemblies Installation Test Dielectric Voltage-withstand Test Manufacturing and Production Tests Performance Tests Key performance tests which concern overvoltage protectors are detailed in the arrester test section. Requirements are: Breakdown Voltage Measurement -Arresters are to be tested in the protector blocks or panels in which they are intended to be employed. Arresters are required to break down within 25% of the manufacturer's specified breakdown rating. In no case shall the breakdown voltage exceed 750 V peak when subjected to the strike voltage test. (Figure 3.13) At no time during this test will the supply voltage be increased at a rate greater than 2000 V/s. Impulse Spark-over Voltage Measurement -The arrester must break down at less than 1000 V peak when subjected to a single impulse potential. Arresters are to be tested in each polarity with a rate of voltage rise of 100 V/s, 10%. Abnormal Operation -Single pair fuseless arresters must be able to simultaneously carry 30 A rms at 480 V rms for 15 minutes without becoming a fire hazard. A fire hazard is determined by mounting the arrester on a vertical soft wood surface and covering the unit with cheesecloth. Any charring or burning of the cheesecloth results in test failure. During this test, although the arresters may short, they must not have an impulse spark-overvoltage or DC breakdown voltage greater than 1500 V peak. Discharge Test -Protectors must comply with the strike voltage requirements after being subjected to five successive discharges from a 2 F capacitor charged to 1000 V dc. (Figure 3.14). Repeated Discharge Test -The arrester must continue to break down at or below its maximum rated breakdown voltage after being subjected to 500 discharges from a 0.001 F capacitor charged to a potential of 10,000 V dc. The interval between pulses is five seconds. Arresters are to be tested in each polarity, and it is acceptable for the protector to short circuit following the discharge testing. (Figure 3.14) Test Specimen C1 R2 10 5 W R1 50,000 25 W Variable DC Supply 0-1000 V V Figure 3.13 UL 497 Breakdown Voltage Measurement Test Specimen Spot Switch C1 R2 10 5 W R1 5 M 50 W Variable DC Supply * 0-12,000 V *Or Voltage Capability Necessary to Develop 10,000 V Across Capacitor V Figure 3.14 UL 497 Discharge Test Regulatory Requirements (continued)

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