This document describes the design of a cooling system for a permanent magnet synchronous motor (PMSM) in an electric vehicle. It discusses how electric motors generate heat from factors like winding resistance and load changes, and why cooling is necessary to maintain efficiency and the lifespan of the motor insulation. It then summarizes two main types of motor cooling systems - air cooling and water cooling. For a high power density motor, water cooling is more suitable. The document outlines the methodology for designing a water-cooled system for the PMSM, including calculating the heat transfer coefficients of the hot and cold fluids, the overall heat transfer coefficient, and using the Normal Transfer Units method to size the heat exchanger.