Rotor assembly and electric water pump

The rotor assembly comprises a rotor part, the rotor part comprises a rotor component and a plastic shell, the rotor component comprises a columnar rotor core with an axial hollow hole and a permanent magnet arranged on the radial surface of the rotor core, the permanent magnet comprises an arc surface L, and the rotor core and the permanent magnet are fixedly connected through the plastic shell. The rotor component is characterized in that in the axial projection, the width of the permanent magnet is W, the thickness of the permanent magnet is H, the diameter of the circumcircle of the rotor component is phi, and the distance between the circle center of the rotor component and the circle center of the arc surface L of the permanent magnet is P, so that W = (0.3-0.4) * phi, H > = 0.095 * phi, and P < = 0.22 * phi. According to the rotor assembly and the electric water pump provided by the utility model, the structures of the permanent magnets and the rotor iron core are optimized, so that when the use amount