Calculation of Parasitic Capacitance to Analyze Shaft Voltage of Electric Motor with Direct-Oil-Cooling System

In modern electric vehicles, electrical failure has become a critical problem that reduces the lifetime of traction motors. Moreover, motors with high-voltage and high-speed systems for high power density have been aggravating shaft voltage problems. This study identifies direct-oil-cooling exacerbate this problem. To address this, an analytical method calculating parasitic capacitance is proposed to determine effects cooling oil in motor system. Capacitance equivalent circuits are configured based on whether slot submerged oil. addition, field decomposition applied analyze distortion by structure conduction parts motor. The results indicate capacitances increased influence resulting increase voltage.