Is terminals temperature of NSX250 DC, still within the limit 120 degree C when NSX250 DC carries 180A at 70 degree C
As per the IEC60947-1 , table 2, the rise-temperature for tin platted copper is 65°K. So at 40°C ambient temperature, the temperature on the terminals will reach at max 40+65=105°C, for a device which is new. Also as per the IEC60947-2, table 7, the rise-temperature for terminals for external connection can reach at max 80°K for a device which has followed test sequences I to VI, So, meaning in fact that the device is almost in end of its life. According the catalogue, for an ambient temperature 70°C, a derating in current must be applied at 180A for NSX250DC TM250DC >500V. Such derating will not allow to exceed 105°C on the device' terminals with 40°C ambient temperature, when the device is new. If the device has operated a lot, combinated with short circuit, as in fact all the tests performed as described in the IEC test sequences, with 80°K, the terminals could reach 40+80=120°C. So the derating in current of 180A defined will allow not to exceed 120°C in such conditions.