Blower-BLDCM 일체형 시스템 설계에 관한 연구

Abstract

Recently, air-electronic appliances have been gaining increased attention as their applications are increasing. These appliances are products or systems that purify polluted air or provide convenience functions using air, e.g., air conditioners, air purifiers, humidifiers, dehumidifiers, air circulators, dryers, clothing stylers, and blowers. The blower is a machine that obtains air volume and pressure by applying energy to the air through impeller rotation; its pressure ratio is generally 1.1–2.0 between the inlet and outlet less than 1.1 at the fan. These are collectively referred to as the blowers, but it is set to the limited range of the blower in this thesis. The appropriate selection and control of the motor is crucial to obtain high-speed and high-volume airflow in a blower. Therefore, the motor is typically separated from the other components of the blower. The brushless direct current (BLDC) motor is gaining popularity because it can be used semi-permanently at high speeds as the motor for the blower of electronic appliances. Although the electrical properties of the BLDC motor are similar to those of direct current (DC) motors, the BLDC motor utilizes electronic DC devices without brushes or commutators, which lowers its maintenance requirements, increases longevity and efficiency, and greatly enhances its vibration and noise characteristics. However, while it can maintain a constant torque, it is challenging to apply high-performance precision control to a BLDC motor owing to torque ripple. In this thesis, computer simulators including SC/Tetra and PSIM were employed to model the airflow of blower–BLDC motor integrated systems and the performance of BLDC motor controllers; subsequently, their feasibility was demonstrated through experimental verification. The main components of the blower–BLDC motor integrated system consisted of a blower, a main body, a pressurizer with a cover plate, an airflow transport path, a plate, and the BLDC motor, designed and manufactured using 2D and 3D models. Eight discharge units were developed to render the airflow into a vortex with a rotation angle of 45° and separate the moisture using the centrifugal force from the difference in specific gravity of the air through a high-speed centrifugal-separation method. The result of the airflow analysis for the blower in the blower–BLDC motor integrated system with the shape and boundary conditions of 120 m/s input in the discharge units, which was performed through SC/Tetra simulation, confirmed that high-speed centrifugation was realized from the vortex-formation of the airflow in the discharge units. The physical airflow experiments were also conducted by measuring the air volume and airflow speed, which revealed that the values were identical to those of the simulation. In addition, the results were represented in terms of the moisture-removal rate by adding water to verify that high-speed centrifugation could be achieved by removing approximately 95.05% of moisture. To reduce the existing zero cross point (ZCP) error that occurs in the BLDC motor while mitigating the torque ripple of the BLDC motor controller in the blower-BLDC motor integrated system, a novel ripple-reduction method was proposed in this thesis. The proposed method detects the back electromotive force, deploys an integrator to linearize the signals of the back electromotive force sensor and remove the signals from the upper and lower parts of the unnecessary back electromotive force, and uses zero-crossing signals to reduce the ripple. As a result, the ZCP error in the controller due to the sampling-position error and speed-variation error of the motor was rectified through the results of both the PSIM simulations and experiments. Through this thesis, further research on airflow analysis and improvement of BLDC-motor controllers of electronic-appliance blowers can be conducted more actively, and consequently, the quality and features of various appliances, such as dryers, dehumidifiers, moisture removers, clothing stylers, air showers, and dustproof facilities, can be improved.