SACE TMAX XT UL/CSA LOW VOLTAGE MOLDED CASE C I RCUI T- BRE AKERS UL4 89 AND CSA C2 2 . 2 STANDARDS
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— Construction characteristics
All the SACE Tmax XT molded case circuit-breakers are built in accordance with the following constructional characteristics.
Positive operation The operating lever always indicates the precise position of the moving contacts of the circuit- breaker, thereby guaranteeing safe and reliable sig- nals, in compliance with IEC 60073 and IEC 60417 Standards (I = Closed; O = Open; yellow-green line = open due to protection trip). The circuit-breaker operating mechanism has a free release regardless of the pressure on the lever and the speed of opera- tion. Protection tripping automatically opens the moving contacts: to re-close them, the operating mechanism must first be reset by pushing the op- erating lever from the intermediate position to the lowest open position.
Double insulation The Tmax XT circuit-breaker has double insulation between the live power parts (excluding the termi- nals) and the front parts of the apparatus where the operator works during normal operation. The mounting location of each electrical accessory is completely segregated from the power circuit, pre- venting any risk of contact with live parts. The op- erating mechanism especially is completely insu- lated from the energized circuits. Furthermore, the circuit-breaker has oversized in- sulation, both between the live internal parts and near the connection terminals. Furthermore, the clearances exceed those required by the IEC Stan- dards and fully comply with the prescriptions of the UL 489 Standard.
Insulation behaviour In the open position, the circuit-breaker guarantees insulation distances in compliance with the UL489 Standard, thus preventing leakage currents to flow between the input and output terminals.
Tropicalization Circuit-breakers and accessories in the Tmax XT se- ries are tested in compliance with the IEC 60068-2-30 Standard, carrying out 2 cycles at 55 °C with the “variant 1” method (clause 7.3.3). The suitability of the Tmax XT series under the most severe environmental conditions is further ensured with hot-humid climate according to climatograph 8 in the IEC 60721-2-1 Standards thanks to: • molded insulating cases made of synthetic resins reinforced with glass fibers; • anti-corrosion treatment of the main metallic parts; • Fe/Zn 12 zinc-plating (ISO 2081) protected by a conversion layer, free from hexavalent chromium (ROHS-compliant), with the same corrosion resis- tance guaranteed by ISO 4520 class 2C; • application of anti-condensation protection for elec- tronic overcurrent trip units and relative accessories.
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