Resistance to vibrations
VD4 circuit-breakers are unaffected by mechanically generated vibrations. For the versions approved by the naval registers, please contact us.
Tropicalization
VD4 circuit-breakers are manufactured in compliance with the strictest regulations regarding use in hot humid-saline climates. All the most important metal components are treated against corrosive factors according to UNI 3564-65 Standards environmental class C. Galvanisation is carried out in accordance with UNI ISO 2081 Standards, classification code Fe/Zn 12, with a thickness of 12x10-6 m, protected by a conversion layer mainly consisting of chromates in compliance with the UNI ISO 4520 Standard. These construction characteristics mean that the whole VD4 series of circuit-breakers and its accessories comply with standards as follows: IEC 60721-2-1 (climate graph 8 ) IEC 60068-2-2 (Test B: Dry Heat ) IEC 60068-2-30 (Test Bd: Damp Heat, cyclic)
Altitude
The insulating property of air decreases as the altitude increases, therefore this must always be taken into account for external insulation of the apparatus (the internal insulation of the interrupters does not undergo any variations as it is guaranteed by the vacuum). The phenomenon must always be taken into consideration during the design stage of the insulating components of apparatus to be installed over 1000 m above sea level. In this case a correction coefficient must be considered, which can be taken from the graph on the next page, built up on the basis of the indications in the IEC 60694 Standards. The following example is a clear interpretation of the indications given above. Graph for determining the Ka correction factor according to the altitude H = altitude in metres; m = value referred to power frequency and the lightning impulse withstand voltages and those between phase and phase
Graph for determining the Ka correction factor according to the altitude
H = altitude in metres; m = value referred to power frequency and the lightning impulse withstand voltages and those between phase and phase.
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