Does the point B.2.6.2 in EN 62368 force to perform temperature measurement for Cause 6 at real Trma (manufactures max allowed ambient temperature of the DUT)?
You asked, does the point B.2.6.2 in EN 62368 force to perform temperature measurement for Cause 6 at real Trma (manufactures max allowed ambient temperature of the DUT) ? Or is it allowed to perform measurement at e. g. 25°C and calculate the resulting temperature at components and parts?
B.2.6.2 covers heating test options for temperature dependent equipment as opposed to non-temperature dependent equipment which B.2.6.3 covers. For temperature dependent equipment, B.2.6.2 provides two options. As noted, the temperature can be measured in an oven at the least favorable temperature as declared by the manufacturer, but not exceeding Tmax. Alternatively, the temperature can be measured in room ambient (e.g. 25°C) with the heating or cooling device at the least effective setting or defeated, again which would need to be identified by the manufacturer.
For compliance with B.2.6.2, because of the nature of equipment designs that incorporate active temperature dependent heating/cooling, including fans that adjust to sensed temperatures, it is not appropriate to adjust temperatures as can be done for passive non-temperature dependent equipment per B.2.6.3.
Due to the variety of active cooling/heating designs that can be associated with B.2.6.2, usually the application of B.2.6.2 requires collaborative discussion between UL and the manufacturer due to the need to determine worst case conditions for temperature dependent equipment.