NVH investigation of automotive HVAC brushless motors

In the automotive industry, thermal systems are of critical importance in securing optimum vehicle operating, preserving battery capacities and ensuring passenger comfort. These systems involve a wide range of components with various technologies, designs and more innovation. Currently, thermal engine market shares are decreasing as facing increasing electrification trends worldwide. Consequently, thermal systems may become major sources of noise and vibration that may emerge inside the car cabin. This may cause significant discomfort to passengers and can create disturbances to passersby outside the car. As a system supplier, Valeo ensures NVH compliance according to internal standards and OEM specifications during development and production stages. However, as electrification trends involve more and more innovations with less technical background, ensuring NVH compliance becomes a formidable challenge to deal with. Among the main NVH sources, the HVAC Brushless motor is highly critical as implanted inside the car cabin. This paper focuses on the main NVH topics encountered on HVAC BLDC motors. First, the NVH sources are analyzed from mechanical and magnetic design perspectives. Furthermore, solutions to control the NVH behavior are presented which sets the product's intrinsic limitations and operating conditions. Finally, from a technical compliance perspective, specification design implications are discussed.