Consulting for CFD Flow & Thermal Calculations
The generation of power from wind turbines and photovoltaic systems, the charging of electric vehicles, and the power supply and control of locomotives all require efficient conversion between direct current (DC) and alternating current (AC). The enclosures for energy systems are usually electrical cabinets housing the rectifiers and inverters as well as ohmic, capacitive, and inductive components. Battery storage units are usually placed in the lower area of the cabinet.
In 2022, 80% of EVs were charged at home or at work from a conventional socket using an AC/DC converter. Fast charging stations are designed for long-distance travel so that EVs can be charged with high power in a short time. The charging infrastructure must be available across the country. Charging stations are supplied with 220 V AC on the input side; a higher voltage supply such as 690 V AC or 800 V AC would make more sense, but that would require additional wiring to be built and licensed. An essential task of the charging station is therefore to increase the voltage. Silicon Carbide (SiC) MOSFETs have largely replaced IGBTs because they have faster switching speeds and lower switching losses. Several charging modules can be assembled in one cabinet to supply several cars at the same time.
Many components are located in the cabinet in addition to the rectifiers and inverters: transformers, coils, resistors, line filters, switches and cables. All components that generate heat must be ventilated. The rectifiers and inverters often have their own cooling systems with axial fans or a water circuit. It is often difficult to maintain the minimum clearances before and after the fans. Often, these distances are not adhered to, although in other areas such as electromagnetic compatibility or filtering the air, standards are strictly observed.
The fans are not fully simulated by rotating the blades in a conventional flow simulation. Instead, the fan curves (pressure rise vs. volume flow) are specified as input data. The measurements of the curves are performed according to "ISO 5801 Industrial fans". These curves usually represent ideal conditions. For normal operation, this curve should typically be derated by 10%. If the distances before and after the fans are not adhered to, then the curves must be derated by 20% or 30%. Even with these corrections, the measured volume flow in the cabinet is often lower than the calculated one.
Photovoltaic (PV) inverters operate daily to convert direct current (DC) from solar panels into alternating current (AC) for home or grid use.
To maintain their performance and longevity, it is crucial to ensure that these inverters do not exceed their specified temperature limits. When the temperature within the enclosure becomes too high,
rather than causing immediate damage to the sensitive semiconductors, most inverters employ built-in safety mechanisms. These mechanisms automatically reduce the inverter’s output power—a process known as "de-rating."
To avoid unnecessary power losses and maintain maximum energy output even under extreme weather conditions, proper ventilation and cooling strategies are essential.
The design of the enclosure should prioritize efficient airflow and heat dissipation, allowing the inverter to operate at full capacity during hot, sunny days without relying on power-consuming air conditioning systems.
