Fig. 1 Components targeted in EV thermal managementFig. 2 Schematic of cooling system1. Introduction2. Challenges in tests for EV thermal 2.1 Increase in test conditionsmanagement*Customer and Vehicle Performance Engineering Division Customer Performance and Vehicle Test Engineering Department No.2Electrification is achieved by a powertrain comprising a motor, inverter, and high-energy battery, which do not exist in conventional vehicles running with internal combustion engines (ICEs) (Figs. 1 and 2, respectively).EVs have reduced heat emission compared to that of ICEs. However, the temperature of these components must be properly controlled to ensure their efficiency and reliability, and thus, thermal management is important.In ICEs, the amount of exhaust heat emitted from the engine is so large that it is used as the primary heat source to warm the room. In contrast, electric vehicles must use battery power to produce heat. Therefore, the inefficient use of power can lead to less power being available for driving. Furthermore, the battery generates heat originating from internal resistance, and its performance and life can be reduced depending on the thermal environment. Therefore, the battery temperature must be controlled properly. The thermal environments of the battery and e-PT must be controlled to achieve a good balance between electricity cost and interior comfort.In ICE tests, operating conditions such as the on/off state of the air conditioner and the amount of heat emitted from the heat-generating engine can be evaluated independently. However, EVs use the cooling energy provided by the air conditioner to regulate the temperatures of the motor, battery, and inverter. Therefore, the electric compressor used by the air conditioner operates not only to switch the air conditioner on and off, but also to respond to the cooling demands of the battery. Furthermore, only the compressor battery cooling operation must be stopped to maintain the battery temperature environment. The combination of these conditions increase the number of driving modes. Further, it is necessary to process a large amount of time-series data obtained from the test because the driving modes change transiently.2.2 Additional requirements for EV cooling systemUnlike an ICE vehicle, an EV cannot use the waste heat for interior heating, and therefore, battery power is used to produce heat. This increases the battery power consumption, which affects the cruising distance. Heat pump systems that use heat from outdoor air have become the norm for indoor heating in EVs to minimize this negative effect. The compressor must be operated at a high rotation speed to sustain cooling by removing heat from outside, not only when high-temperature outside air is present but also when low-temperature outside air is present. An electric compressor can be operated at any desired rotational speed; however, the noise of the compressor and other cooling components must be maintained at a low value to ensure a low-noise 575. Test Technology for Thermal Management System Achieving Both Low Electricity Cost and High ComfortMasayoshi Tajiri*
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