馬達產生之微粒排放特性

Abstract

家用電器內的馬達是生活中最常見的驅動器之一，其功能是將電力轉為機械力，藉此驅動風扇或是特定的設備，然近年來越來越多研究顯示，安裝於室內電器的微型馬達，能觀察到微粒的產生，這些細小微粒容易被人體吸入，並且沉積在支氣管或是肺部等區域，對於人體的健康有很大的疑慮。而家用電器運作時距離人體很近，容易造成更高的暴露危害，因此需要對馬達產生的微粒進行評估，而過去的研究報告所提供之資訊僅能凸顯馬達確實是重要的微粒產生源，卻未有量測馬達產生微粒的標準方法，因此本研究會先建立方法以評估馬達在不同參數下的微粒的產生特性，並探討馬達微粒產生的機制，提出解決馬達微粒排放問題的策略。 本研究首先會先建置一實驗系統，使用數顆同一廠牌的直流有刷馬達以及直流無刷馬達進行實驗，並以實驗確認微粒量測的準確度且能完整的量測馬達所產生的微粒數目，再藉由改變各項參數了解對馬達微粒排放的影響。微粒產生機制的確認則是使用相同型號的馬達(Motor2)來帶動待測馬達(Motor1)，希望透過主動運轉(供電給Motor1)及被動運轉(供電給Motor2)來區分火花放電以及機械磨損這兩種馬達產生微粒的主要機制，並以電子顯微鏡觀察馬達所產生的形狀及成分。最後量測市售電動刮鬍刀所產生的微粒特性。 為了解系統所需的稀釋流量，測試了在不同轉速下稀釋流量對馬達產生微粒濃度的影響，再計算馬達每秒的微粒產生率來評估是否能量測到所有馬達產生的微粒。結果表明，直流有刷馬達產生的微粒排放率會隨著稀釋流量提高而提升，當稀釋流率大於10 L/min後趨於穩定，並將系統的稀釋流率訂為12 L/min。針對直流有刷馬達產生微粒兩種可能機制分別是火花放電以及機械摩擦進行探討，研究結果指出火花放電是馬達產生微粒的主要原因，經由火花放電產生的微粒數目每秒約為2.1*107顆約為機械摩擦產生的250倍，粒徑落在40 nm，同時量測了直流無刷馬達的微粒產生率與粒徑，結果表明直流無刷馬達每秒依舊會產生2.2*104顆微粒，約為直流有刷馬達產生的微粒的千分之一，粒徑約為120 nm，且直流有刷馬達以及直流無刷馬達的微粒產生率皆會因為轉速提高而上升，在電動刮鬍刀的實驗中也驗證了轉速提高會影響產生的微粒數目濃度，此外亦發現防水的外殼可以有效的減少馬達產生的微粒逸散。

Motors in household appliances are among the most common actuators in daily life, converting electrical energy into mechanical force to drive fans or specific devices. However, recent studies have shown that miniature motors installed in indoor appliances can generate particles. These fine particles are easily inhaled and can deposit in the bronchi or lungs, raising significant health concerns. Since household appliances operate close to the human body, the risk of exposure is higher, necessitating an evaluation of the particles generated by these motors. Previous research has highlighted that motors are indeed significant sources of particle emissions but has not provided a standard method for measuring these emissions. Therefore, this study aims to establish a method to evaluate the particle generation characteristics of motors under different parameters, investigate the mechanisms of motor particle generation, and propose strategies to mitigate particle emissions from motors. This study will first establish an experimental system using several DC brushed motors and DC brushless motors from the same manufacturer. The experiments will verify the accuracy of particle measurements and ensure a comprehensive assessment of the number of particles generated by the motors. By varying different parameters, we aim to understand their impact on motor particle emissions. To confirm the particle generation mechanisms, we will use an identical model motor (Motor2) to drive the test motor (Motor1). By comparing active operation (powering Motor1) and passive operation (powering Motor2), we hope to distinguish between spark discharge and mechanical wear as the primary mechanisms of particle generation. An electron microscope will be used to observe the shape and composition of the particles generated by the motors. Finally, we will measure the particle characteristics produced by commercially available electric shavers to validate the experimental results. To determine the necessary dilution flow rate for the system, we tested the impact of dilution flow rates on particle concentrations generated by the motor at different speeds. We then calculated the particle generation rate per second to evaluate whether all particles produced by the motor could be measured. The results showed that the particle emission rate of the DC brushed motor increases with higher dilution flow rates and stabilizes when the flow rate exceeds 10 L/min. Consequently, we set the system's dilution flow rate to 12 L/min. We explored the two potential mechanisms of particle generation in DC brushed motors: spark discharge and mechanical friction. The study results indicated that spark discharge is the primary cause of particle generation. Particles generated by spark discharge amount to approximately 2.1 x 107 particles per second, about 250 times the number produced by mechanical friction, with a particle size of around 40 nm. We also measured the particle generation rate and size for DC brushless motors. The results show that DC brushless motors still produce particles, generating about 2.2 x 104 particles per second, which is roughly one-thousandth of the particle count generated by DC brushed motors, with a particle size of around 120 nm. The particle generation rates for both DC brushed and brushless motors increase with higher speeds. In experiments with electric shavers, we confirmed that increasing the speed affects the particle concentration. Additionally, we found that a waterproof casing can effectively reduce the dispersion of particles generated by the motor.