I. Introduction
Although some achievements have proposed to solve the problems related to normal machines vibration. However, few types research on high power PMSM are carried. Generally speaking, a high power machine(above 300 KW) has a big stator slot and poor slot factor. So it is common to use a rotor acting as a hollow structure to reduce its quality. Which will influence both its strength and stiffness. Furthermore, the low-speed direct-drive style will bring some new problems [1]–[3].