energies Article Study of Injection Method for Maximizing Oil-Cooling Performance of Electric Vehicle Motor with Hairpin Winding Taewook Ha 1 and Dong Kyu Kim 1,2,* 1 School of Mechanical Engineering, Chung-Ang University, Seoul 06974, Korea;
[email protected] 2 School of Computer Science and Engineering, Chung-Ang University, Seoul 06974, Korea * Correspondence:
[email protected]; Tel.: +82-02-820-5192 Abstract: The oil injection method was studied to maximize the cooling performance of an electric vehicle motor with a hairpin winding. The cooling performance of the motor using the oil cooling method is proportional to the contact area of the oil and the coil. A numerical analysis was conducted to examine the effect of the spray nozzle type on the oil flow. The dripping nozzle forms the thickest oil film on the coil, making it the most effective for cooling of hairpin-type motors. Subsequently, an experimental study was conducted to optimize the nozzle diameter and number of nozzles. When the inlet diameter and number was 6.35 mm and 6, the oil film formation rate was 53%, yielding the most uniform oil film. Next, an experiment was performed to investigate the effects of the oil temperature and flow rate on the oil flow. The oil film formation rate was the highest (83%) when the oil temperature was 40 ◦C and the flow rate was 6 LPM. Keywords: electric vehicle; hairpin winding; motor cooling; oil cooling; injection method 1. Introduction Citation: Ha, T.; Kim, D.K. Study of In recent years, interest in environmental issues has increased, accelerating the de- Injection Method for Maximizing velopment of electric vehicles and increasing their demand.