10/07/2023The main trend in the field of chargers of electric cars and other vehicles with electric drive is development and implementation of so called fast DC-charging stations. Compared to the already traditional charging stations with AC output – AC charging stations, they are able to reduce the time of full charge to several hours or less. For electric car owners, often business owners, the reduced charging time is a direct money saver. For their iron (or is it plastic already?) horses, it is a reduction in the weight of the on-board equipment (no charger required on board) and, as a consequence, an increase in the life of the car, improved vehicle dynamics and a noticeable reduction in its cost.
But, for such attractive benefits, in general you have to significantly complicate the charging stations and convert them to constant voltage output up to several hundred volts. Typical power outputs become 20…30…50… and even 150 kW or more. Obtaining such large powers with high reliability in almost open outdoor environments, rain, low and high temperatures, etc., even with modern SiC semiconductor element base is a difficult task. A typical technique in most cases is the parallel redundancy of AC/DC power modules in an N+1 or N+2 system.
ALEXANDER ELECTRIC developed two series of planar AC/DC power modules for critical missions: operation in wide temperature range, limited heat sink, sand, dirt, salt spray, damaged sealing of equipment compartments, etc., operation with single-phase and three-phase networks in parallel N+M redundancy modes. In serial production, these products were mastered in 2020 and are very relevant for use in DC charging stations of a wide range of electric-powered mobile vehicles.
The flagships of the series are the JETA3000-LP single-phase AC modules, the JETNA5000-LP three-phase modules for a maximum power of 3kW and 5kW respectively.
Fig. 1 – JETNA5000-LP AC/DC three-phase power supply unit for DC-charging stations up to 40 kW (10 modules in parallel with 2 redundant)
Temperature range of the modules is -60°C…+100°C. In spite of the high efficiency of these AEPS-group products, the actual problem is the necessity of heat removal from the charging station enclosure. At full load of 40 000 kW for 10 modules at 5000 kW each we have for efficiency = 0.95-0.96 kW thermal power, which should be dissipated 2.11 kW … 1.67 kW.
For this purpose all available types of cooling of the charging station can be used: conductive heat sink on the housing (alas, aluminum and not thin-walled!), liquid cooling and finally traditional fans.
Fig. 2 shows schematically a combination of sufficiently thick radiator bases for developed conductive heat dissipation and ribbed parts of the heat sink. Heat dissipation is made easier by the ultra-flat, planar design of the JETNA series power modules.
Fig. 2 – A simplified type of modular power supply for DC-charging stations of electric cars with a capacity of 30 kW.
The result is that about 93% of the heat from each module travels through the sole of the module to the conductive heat sink of the cooling system and only 7% of the heat is released in the opposite direction. The design itself is very compact and practical.
Typical parameters of the input network is 3-phase 380 … 415 V, 50 … 60 Hz, the converter efficiency of 95%, output voltage 60 … 500 V (DC) depending on the model, the output power up to 40 kW. The construction of charging stations based on JETNA5000-LP modules makes it possible to comply with CHAdeMO / IEC 61851-1 / IEC 61851-23 standards. Due to the unique temperature characteristics of the JETNA5000-LP modules, the ambient temperature can reach -60°C … +100°C !
AEPS-group products have been successfully tested in real conditions – in the extreme minus temperatures of the Arctic and Antarctica, in the mountains at different altitudes, in cold and hot deserts, in fog conditions.
