NKMP11-4
IEC 60890和IEC 61439-1标准规定，该计算方法仅在满足以下条件时适用：-组装电路的额定电流不得超过保护装置和安装在电路中的电气部件额定电流（在自由空气中）的80%；-外壳内部的功率损耗分布大致均匀，并且没有阻碍其向组件外部扩散的障碍物；-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电，高可达60 Hz，总供电电流不超过1600 A；-承载电流超过200 A的导体和结构部件的布置应确保涡流损耗可忽略不计对于带有通风孔的外壳，出风口的横截面至少为进气口横截面的1.1倍；-组件的每个部分不超过三个水平隔板；-如果带有外部通风孔的外壳被划分为隔间，则每个内部水平隔墙中的通风孔表面应至少等于隔间水平截面的50%。为了计算外壳内空气的温升，一旦满足标准要求，就必须考虑以下因素：-外壳尺寸-安装类型：-外壳四面向空气开放；-壁挂式外壳；-设计用于安装在四肢的外壳；-多隔间开关板内部位置的外壳；-任何通风孔及其尺寸——水平内部分离器的数量——通过安装在配电盘或隔间内的任何装置和导体的有效电流产生的功率损失。该标准允许计算配电盘中间高度和高点的空气温升。一旦绘制了组件内部从下到上的热图，如果任何设备安装高度处的计算空气温度不超过设备制造商声明的允许环境空气温度，则验证组件。这意味着，对于主电路中的开关设备或电气部件，连续负载不超过其在计算的局部空气温度下的允许负载，且不超过其额定电流的80%。附录B解释了标准中描述的计算方法。ABB为客户提供计算软件，可以快速计算配电盘内部的温升

NKMP11-4
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. To calculate the temperature rise of the air inside an enclosure, once the requirements f the Standard have been met, the following must be considered: - Dimensions of the enclosure - Type of installation: - enclosure open to air on all sides; - wall-mounted enclosure; - enclosure designed for mounting in extremities; - enclosure in an internal position in a multicompartment witchboard; - Any ventilation openings, and their dimensions - Number of horizontal internal separators - Power losses from the effective current flowing through any device and onductor installed within the switchboard or compartment. The Standard allows the calculation of temperature rise of the air at mid-height and at the highest point of the switchboard. Once the thermal map of the inside of the assembly from bottom to top has been drawn, the assembly is verified if the calculated air temperature at the mounting height of any device does not exceed the permissible ambient air temperature as declared by the device manufacturer. This means for switching devices or electrical components in the main circuits that the continuous load does not exceed its permissible load at the calculated local air temperature and not more than 80 % of its rated current. The Annex B explains the calculation method described in the Standard. ABB supplies the client with calculation software which allows the temperature rise inside the switchboard to be calculated quickly