tailieunhanh - Advances in Vibration Analysis Research Part 11

Tham khảo tài liệu 'advances in vibration analysis research part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A Plane Vibration Model for Natural Vibration Analysis of Soft Mounted Electrical Machines 289 stator orbit is shifted about 47 out of the horizontal axis. The semi-major axes of the orbits of the bearing housings are shifted about 62 out of the horizontal axis. All orbits are still run through forwards. In the 5th mode the semi-major axis of the orbit of the rotor mass is shifted about 12 out of the vertical axis. The other orbits lie nearly in vertical direction. The stator mass and the rotor mass oscillate out of phase to each other. The orbit of the stator mass and the orbits of the bearing housing are run through forwards while the orbit of the rotor mass and the orbits of the shaft journals are run through backwards. In the 6th mode the semi-major axes of the orbits of the stator mass and of the bearing housings are shifted about 80 out of the vertical axis while the semi-major axes of the orbits of the rotor mass and of the shaft journals are shifted about 45 out of the vertical axis. All orbits are run through backwards. Additionally the 6th mode shows a strong lateral buckling of the stator mass at the x-axis which leads to large orbits at the motor feet. Contrarily to the 1st mode the lateral buckling of the stator mass is contrariwise to its horizontal movement which means that if the stator mass moves to the right the lateral buckling is to the left. To consider the influence of the foundation damping on the natural vibrations a simplified approach is used. Referring to Gasch et al. 2002 the damping ratio Df of the foundation can be described by the damping coefficients dfq stiffness coefficients cfq of the foundation and the stator mass m. as a rough simplification. dfq Df ms-yl2 cfq ms with q z y 50 The calculated natural frequencies and modal damping of each mode shape with and without considering foundation damping are shown in Table 3. It is shown that considering the foundation damping influences the natural frequencies only marginal as expected.

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