2.18 SCHALTGERÄTE Wissenswertes von A-Z Know How from A - Z manufacturing for parts that are built onto the engine such as suction systems, fuel pipes, engine covers etc. The two most frequently used polyamides are PA 6 and PA 6.6. Their manufacturing process is fundamentally different. PA 6.6 and PA 6 are nevertheless chemically and physically very similar and differ only in their mirrored arrangement of one CH2-NH-CO group. Polycarbonates (PC) are synthetic polymers from the polyester family. Polycarbonates are crystal clear, can be coloured, welded and glued and are also very dimensionally stable and possess high impact resistance. Because of its higher cost relative to other plastics, polycarbonate is almost only used where others are too soft, too brittle, too prone to scratches, insufficiently dimensionally stable or not sufficiently clear. PC also excels for its high UV resistance and good electrical characteristics. MERZ uses PC for the enclosure series I7 and higher. Polystyrol (PS) other names: polystyrene, IUPAC name: poly(1-phenylethane-1,2-diyl)) is a transparent, amorphous or partially crystalline thermoplastic. PS can be dyed in all colours. Amorphous polystyrol is a common plastic that finds application in many areas of everyday life. Polystyrol is used either as a thermoplastically workable raw material or as an expanded material. In electrical engineering polystyrol is used for its good insulating qualities. As well as for the insulation of cables it is used in the manufacture of switches, bobbins and housings (high-impact polystyrene, HIPS) for electrical equipment. Admittedly PS is only limited UV-resistant. Therefore it is not usable for outdoor use. PS is used for the production of the series 89xx and I1-S up to I3-S. Positively driven operation According to IEC/EN 60947-5-1 positively driven contacts must guarantee, that the contacts are completely opened as a direct result of a defined movement of a switch actuator without springloaded parts, when the actuator has travelled the forced disconnection travel at a manufacturer specified force. Pulse contacts Pulse contacts are used for additional triggering mostly of contactors or relays. In particular motor controls utilise pulse contacts for activating an additional net-relay. Rated breaking capacity Rated value of current, a switching device can satisfactorily break corresponding to its utilization category. The rated breaking capacity is stated by reference to the rated operational voltage and rated operational current according to the relevant device norm. A switching device must be capable of breaking any value of current up to and including its rated breaking capacity. IEC/EN 60947-1; 4.3.5.3 Rated conditional short-circuit current (of a circuit or a switching device) Iq From the manufacturer declared unaffected current, that a switching device (e.g. switch-disconnector), protected by a manufacturer specified short-circuit protective device (e.g. motor protection switch), can carry during the disconnecting time of such device under in the individual device norm specified testing conditions. The manufacturer must specify the details of the short-circuit protective device. IEC/EN 60947-1; 4.3.6.4
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