评估组件内部的温升；标准IEC 60890
IEC 61439-1规定该计算方法仅适用
当满足以下条件时：
组装电路的额定电流不得超过额定电流的80%
保护装置和电气部件的电流（在自由空气中）
安装在电路中；
•外壳内的功率损耗分布大致均匀
没有任何障碍阻止其向外部扩散
大会；
•安装的总成的布置应确保空气循环几乎不受阻碍；
•安装的总成设计用于直流或交流
包括60 Hz，总供电电流不超过1600 A；
•承载电流超过200 A的导体和结构部件
涡流损耗可忽略不计；
•对于带有通风孔的外壳，排气口的横截面
开口至少为进气口横截面的1.1倍；
•每个部分的水平隔墙不超过三个
装配
•是否应将带有外部通风口的外壳划分为
每个内部水平隔墙中的通风孔表面应至少等于
隔间
计算所需的数据包括：
-外壳尺寸：高度、宽度、深度；
-外壳的安装类型（见表8）；
-存在通风孔；
-内部水平隔板数量；
-安装在外壳中的设备的功率损耗（见表13和
14);
-外壳内导体的功率损耗，等于
根据表1、2和3，每个导体的功率损耗。
对于未满载的设备和导线，可以评估
功率损耗为：
哪里：
P为实际功率损耗；
Pn编号
是额定功率损耗（Ir时
);
我
b为实际电流；
我
n
是额定电流。

to evaluate the temperature rise inside an assembly; the Standards IEC 60890 and the IEC 61439-1 establishes that this calculation method is applicable only when the following conditions are met: the rated current of the assembly circuits shall not exceed 80% of the rated current (in free air) of the protective devices and of the electrical components installed in the circuit; • there is an approximately even distribution of power loss inside the enclosure and there are no obstacles preventing its dispersion towards the outside of the assembly; • the installed assembly is arranged so as that air circulation is little impeded; • the installed assembly is designed for direct or alternating currents up to and including 60 Hz, with the total of supply currents not exceeding 1600 A; • the conductors carrying currents exceeding 200 A and the structural parts are so arranged that eddy current losses are negligible; • for the enclosures with ventilation openings, the cross-section of the air outlet openings is at least 1.1 times the cross-section of the air inlet openings; • there are no more than three horizontal partitions for each section of the assembly; • should the enclosures with external ventilation openings be divided into compartments, the surface of the ventilation openings in every internal horizontal partition shall be at least equal to 50% of the horizontal section of the compartment. The data necessary for the calculation are: - dimensions of the enclosure: height, width, depth; - the type of installation of the enclosure (see Table 8); - presence of ventilation openings; - number of internal horizontal partitions; - the power loss of the equipment installed in the enclosure (see Tables 13 and 14); - the power loss of the conductors inside the enclosure, equal to the sum of the power loss of every conductor, according to Tables 1, 2 and 3. For equipment and conductors not fully loaded, it is possible to evaluate the power loss as: where: P is the actual power loss; Pn is the rated power loss (at Ir ); I b is the actual current; I n is the rated current.