전기자동차 구동을 위한 BLDC 고효율 모터 개발에 관한 연구

Abstract

ABSTRACT

A Study on the Development of BLDC High Efficiency Motor for Electric Vehicle Drive

By Jung, Bo-Won Advisor : Prof. Cha, Yong-Hun, Ph.D. Department of Mechanical Engineering Graduate School of Chosun University

In the past, the automobile industry market showed off the large displacement and high-power & high-performance technical power focusing on internal combustion engine. Due to the instability of oil price, however, it started developing/mass-producing vehicles with low displacement & high fuel-efficiency. Thus, the domestic automobile industry is continuously growing into the national core industry by developing vehicles with low displacement & high fuel-efficiency. However, because of car exhaust after using fossil fuels for a long time, the environmental problem is largely highlighted, and the issue of climate change was discussed with the development of automobile industry. Therefore, the environment-friendly trend could be found in the recent world automobile industry. On top of electric car, the R&D of environment-friendly vehicles such as fuel cell vehicle and hybrid vehicle is actively performed. In case of environment-friendly vehicles, they are driving only with electric motor without engine, or the engine and electric motor are composed as serial, parallel, or serial-parallel. When driving, the high-efficiency driving is possible by combining engine and electric motor. When braking, as equipped with the regenerative braking ability to collect energy, the fuel-efficiency could be improved more than 50% compared to the existing vehicles. The representative cases of environment-friendly vehicle include hybrid vehicle, fuel cell vehicle, and electric vehicle driven by electric motor. Among them, the electric motor application technology which is the most core technology is represented as the technology of environment-friendly vehicle, so that the technical demand for it is increasing. In the world motor technology area, products for microminiaturization, high-speed, high-efficiency, high-power, and light-weight are rapidly growing. Especially, with the increased interest in environment, environment-friendly products are forming new markets. There have been active reinforcement of regulations and technical development to meet such demands for this R&D and also to reduce power consumption. Especially, due to the intensified environmental problem, drivers' interest in electric vehicle is increasing. The great amount of subsidies from government/local governments is also a factor that promotes the purchase of electric vehicles. Moreover, once the autonomous function is added to no noise, no exhaust, light-weighted engine design, and high-tech driver's seat, it is the model of the 4th industrial revolution. Currently, for the development of BLDC motor using the semiconductor switching element after removing the commutator and brush, on top of motor manufacturing businesses in the core parts industry of future automobile, even home-electronic motor manufacturers and industrial motor manufacturers are jumping in the business based on their great interest in researches on product development and quality improvement. Compared to the brush-type DC motor, the BLDC motor has better durability, and high-efficiency and high-power. As there is no brush, the electric noise and mechanical noise are less, so that there is no need of maintenance/repair work. On top of high-speed, its reliability is also high. Compared to other DC motors and AC motors, the BLDC motor has more strengths as a driving motor of electric vehicle. In spite of its high price, it has a long life and great efficiency, so that it has been a lot researched as a driving motor of electric vehicle. This paper aimed to develop the BLDC motor & driver as a driving system of 60kW-level electric vehicle. Completing the development of motor & controller for the PWM control in accordance with high-performance speed control of BLDC motor drive, the Maxwell Program was used for the detailed interpretation of the designed motor. Using the dynamo measuring system, the performance relation of motor efficiency was verified. The results of a series of motor performance test are like below.

1. In order to measure the test results of maximum output, the inverter input was measured as input voltage(VDC) 310V. The motor output was torque(Nm) 102.933Nm, the rated revolutions were 5,560rpm, and the rated output was(KW) 60.02KW.

2. In the results of the motor performance assessment by changing the angle of hall sensor by 5°, 10°, and 15° after producing a BLDC motor, when the speed value was high, and the values of torque, voltage, and watt were low, the performance efficiency was the highest.

3. In the results of dynamo test, when changing the angle of hall sensor by 5°, the maximum torque was 102.933Nm. When the maximum revolution speed was 5,560rpm with voltage(308.1V) and watt(60.02KW), the motor showed the maximum efficiency, which verified the excellence of the motor.

As PWM has high efficiency, high power-factor, and high performance, it gets the limelight in the application area of drive. As the motor could be driving in a certain torque area, certain output area, and extensive driving speed range, more things could be expected from future researches. Owing to the excellent control algorithm in the aspect of responsiveness, linearity of control, switching frequency, and high-frequency percentage of output current, it is applied to many drive systems. In the future, regarding the BLDC motor & drive system for high-performance & high efficiency electric vehicles, it is expected to apply the technology to auto part-related companies, and also to contribute to the commercialization of environment-friendly electric vehicles.