VD4-17.5
Normal Operating Conditions
Ambient Air Temperature
• Maximum +40℃
• Average over 24 hours not exceeding +35℃
• Minimum (Indoor) -5℃
Note: -25℃ operating temperature option available.
Humidity
• Average relative humidity over 24 hours not exceeding 95%
• Average water vapor pressure over 24 hours not exceeding 2.2 kPa
• Average relative humidity over 1 month not exceeding 90%
• Average water vapor pressure over 1 month not exceeding 1.8 kPa
Altitude ≤1000 m.
Seismic Performance
Seismic intensity not exceeding magnitude 8.
Adaptability to Humid Tropical Climates
VD4 circuit breakers are designed/manufactured in strict accordance with standards and can be used in humid, hot, and high-salinity climates. All critical components are specially treated to withstand the corrosion of Class C ambient environments specified in EN 12500 class 5. The galvanizing process is carried out according to UNI ISO 2081 standard, classification number Fe/Zn 12, with a thickness of 12 μm, and color chromate passivation is performed according to UNI ISO 4520 standard.
Altitude: The insulating properties of air decrease with increasing altitude; therefore, the impact of this phenomenon on the external insulation of the switch must be considered when using it at high altitudes. The insulation inside the arc-extinguishing chamber is not affected, as its insulation capacity is guaranteed by vacuum.
If the switch is installed in an area above 1000 m altitude, the effect of altitude should be considered during the design phase of the insulation components.
In this case, a correction factor must be considered, which can be found in the chart on the right, based on the IEC 62271-1 standard. An example calculation based on the above correction principle is given below. Example:
• Installation Altitude:
• Rated Voltage:
• Power Frequency Withstand Voltage:
• Lightning Impulse Withstand Voltage:
2000 m
1 2 kV
4 2 kVrms
75 kVp
• Ka coefficient, found from the chart: Ka=1.13
From the above parameters, the components must be able to withstand (test conditions at zero altitude):
• Power Frequency Withstand Voltage: 42 x 1.13 = 47.5 kVrms
• Lightning Impulse Withstand Voltage: 75 x 1.13 = 84.7 kVp
The above calculations show that circuit breakers used in high-altitude areas must be able to withstand higher insulation level tests at zero altitude. For specific circuit breaker selection, please contact the manufacturer.

MAECENAS IACULIS
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ADIPISCING CONVALLIS BULUM
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