Circuit breaker ambient temperature

Update date:2018-06-27 Source:MAXGE

Circuit breaker ambient temperature

The overload protection of low-voltage circuit breakers is accomplished by means of a thermal release. Normally, the thermal release current rating of low-voltage circuit breakers is based on the manufacturer's IEC898 standard and is set at a reference temperature of 30°C (2 conditions. 

circuit breakers

Thermal release is Made from a set of bimetals, when the circuit is overloaded, the overload current flows through the heating resistance wire, causing the bimetal to deform by heating, bending the top of the hook, and opening the low-voltage circuit breaker contacts. The release device has a direct relationship with the ambient temperature, if the ambient temperature changes, it will cause the rated current value of the low-voltage circuit breaker to change.


The low-voltage circuit breaker is usually arranged in an orderly manner on the switchboard, and then installed in the distribution box. The installation of the distribution box is divided into two types: surface-mounted and concealed-mounted, and the cooling effect of the assembled electric box is better than that of the dark-assembled electric box, and the air in the dark assembly box is not suitable for convection, and the cooling effect is poor. As a result, the ambient temperature of the air in the distribution box rises due to the temperature rise of the low-voltage circuit breaker.


Therefore, the actual operating temperature of low-voltage circuit breakers is about 10°C-15°C higher than the ambient temperature. Therefore, when the ambient temperature is greater than or less than the calibration temperature, we must correct the rated current value of the low-voltage circuit breaker according to the temperature and current-carrying capacity correction coefficient table provided by the manufacturer.

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