Simplified Modeling of Electrical Cabinets

Abstract

Calculating temperature inside an electrical cabinet by the use of e.g. VDI or ASHREA standards for sizing HVAC systems is not adequate because they are intended for: (i) sizing economically optimal HVAC systems, (ii) specific climate, (iii) average environment wind conditions, and (iv) typical building constructions. Electrical cabinets should secure functioning of electrical equipment in extreme weather conditions with as economical design as possible. This paper aims to present a relatively simple procedure to model temperature inside electrical cabinets and to analyze different cabinet constructions depending on the weather conditions. The model principle is based on seven dependent energy balances: on each side of a cabinet and of the airflow through it. Two different wall constructions as well as forced and natural ventilation of a cabinet were analyzed. The goal is to avoid using air conditioning systems in electrical cabinets and to use only if necessary fans or electrical heaters. Insulation of walls is suitable for colder continental climates whereas the use of walls consisting of two metal sheets, with air circulating freely between them, is suitable for hotter continental climates for the equipment with heat dissipation inside cabinets of up to 120 W/m 3.