2009-01-1310 Development of Power Control Unit for Compact-Class Vehicle Natsuki Nozawa, Takeshi Maekawa, Shigeyuki Nozawa and Ken Asakura Toyota Motor Corporation Copyright © 2009 SAE International ABSTRACT Toyota Motor Corporation has developed the new compact-class hybrid vehicle (HV). This vehicle incorporates Toyota Hybrid System II （THS-II）to improve fuel efficiency. For this system we have developed a new power control unit (PCU) that features size reduction, light weight, and high efficiency. We have also improved the ability to mass produce these units with the expectation of rapid popularization of HV. The PCU, which plays an importa nt role in THS-II, is our main focus in this paper. Its development is described. INTRODUCTION Mobility is the base of the human society and economic activity, and widely contributes to society. Meanwhile, it has also brought the important issues of global warming and air pollution induced by CO2 emissions. Therefore, the development of environment- conscious vehicles that are fuel-efficient and have low-emissions is an urgent task today. To solve these issues, Toyota has been working to develop and popularize Hybrid Vehicles (HV). The debut of 1 st generation HV-the world’s first mass produced HV- was in 1997, doubled fuel efficiency compared with the gasoline vehicles. In 2003, a high voltage system using a boost converter was introduced as 2nd generation HV, achieving high-power and low-fuel consumption. The new compact-class HV has been developed this time as a leader of 3rd generation HV, achieving the highest global standards, 50 mpg (US comb.) with high- power and low-fuel consumption. This HV system has the newly developed 3rd generation power control unit (PCU), and is optimized to make the most of the performance of a 1.8L engine and a high-speed, high-power motor. This PCU contributes to downsizing the motors by increasing the maximum system voltage from 500V to 650V, also improving the system efficiency. A direct cooling type has been employed into cooling system of Intelligent Power Module (IPM), achieving size reduction and lighter weight by greatly improving the cooling efficiency. This size reduction and lighter weight easily enables the PCU adoption into multiple models, enabling the rapid popularization of HV. In addition, the structure design focused on ease of mass production and increased quality. This paper explains the specific technology of this 3 rd generation PCU. Fig. 1 The 3rd generation PCU PCU SPECIFICATIONS AND STRUCTURE HV System Specification – The new HV system has increased the maximum voltage of the boost converter from 500V to 650V, as shown in Fig.2. The higher voltage enabled the use of a high-speed, high power of motor with motor speed reduction device. The higher boost voltage leads to downsizing and system efficiency improvement. Table1 shows the specifications of HV system. Motor maximum output has been increase to 60kW, improving the power performance. SAE Int. J. Passeng. Cars - Electron. Electr. Syst. | Volume 2 | Issue 1 376Downloaded from SAE International by Univ of California Berkeley, Wednesday, August 01, 2018 Higher system efficiency improves fuel consumption by around 14% at 100km/h. ■Current model 500V200V 650V200V■New model （3rdgeneration ） Motor MotorGenerator GeneratorBoost Converter Boost ConverterBattery Battery Fig. 2 Composition of HV system Table 1 Specification of HV system PCU Specification - The table2 shows the PCU specifications. The PCU ma x output has been improved around 10%. The RMS, current of the motor inverter has been reduced from 230A(rms) to 170A(rms) by using higher boosted voltage and the motor speed reduction device. The reduced current enables loss reduction and power semiconductor downsizing. In addition, volume is reduced by 37% and mass by 36% due to the newly developed IPM direct cooling, thin