The Calculation Of Critical Speed And Application In Designing Rotor Electric Motor

Motors with low noise and low vibration are increasingly in demand due to environmental considerations. The primary source of noise of these motors is electromagnetic vibration. So in designing electric machines for low vibration and noise, the accuracy of the natural frequencies of the motor is of great importance, since it is essential to avoid coincidence between these frequencies and those of the exciting forces.When the speed of electric motor is near the critical speed, the electric motor will produce the serious resonance phenomenon. The resonance will cause the damage of parts of rotor or rotor, even the whole machine system. Therefore, in the process of electric motor designing, should compute the critical speed, insure the speed of electric motor certainly keep off critical speed to avoid produce resonance phenomenon.Firstly, study the basic theory of the rotor critical speed and summarize some calculation method of the rotor critical speed. Then, to take a YKS560-2 22040kW 6kV asynchronous motor as an example, introduce the application of the calculation method during the process of design and manufacture.The results of the paper present an effective way in studying and designing AC motors for low vibration and noise levers.