Rotational speed characteristic of rotor immersed in oil within an electric motor-pump

Aimed at the decline of the rotational speed of rotor in an 11 kW electric motor-pump prototype, the rotational speed characteristic is calculated by means of experiments, theoretical calculations and RMxprt module of Ansoft software. The study shows that viscosity load, which mainly contains air gap and sealing gap, causes the on-load starting, and affects the decline of the rotational speed to some extent. The power loss caused by the viscosity load is 1.185 kW when the oil temperature is 31t, and the power loss decreases rapidly with the increase of oil temperature. Squirrel-cage resistance has a much impact on the rotational speed. The rotational speed and the total power of the electric motor-pump prototype can be improved by adopting squirrel-cage rotor's material with lower resistivity and enlarging the diameter of the rotor-bar and the end-ring.