Exzentrizit�tsfelder als Ursache von Laufinstabilit�ten bei Asynchronmaschinen

2010

Speedam 2010

The paper shows a theoretical analysis of the shaft vibrations in two-pole induction machines, caused by a static rotor eccentricity. By neglecting field damping effects and considering maximum homopolar flux, a maximum radial magnetic force is calculated -as a worst case -acting on the rotor in the direction of the smallest air gap and oscillating with double supply frequency. This magnetic force is implemented into a simplified analytical rotor dynamic model, considering the oil film stiffness and the damping of the sleeve bearings. Based on this model the equations of motion of the shaft centre and the shaft journals are derived and the orbit movements are mathematical described. Additionally the paper shows that elliptical orbit movements of the rotor occur and that the amplitudes of the shaft vibrations are not only influenced by the magnitude of the magnetic force but also by the direction of the magnetic force.

Section: Rotor Dynamic Modelmentioning

confidence: 99%

“…Therefore it is necessary to consider not only mechanical forces, caused by e.g. mechanical unbalance, but also the electromagnetic forces [1][2][3][4][5][6][7][8][9][10][11]. Beside the excitations, which occur with the rotary frequency -e.g.…”

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of shaft vibrations in two-pole induction machines considering static rotor eccentricity

2010

Speedam 2010

“…mechanical unbalance and misalignment . The characteristic of induction machines is, that beside these mechanical excitations, also electromagnetic excitations occur, which are mainly caused by an unequal air gap between rotor and stator . An unequal air gap leads to electromagnetic forces, which excite the induction rotor to vibrate.…”

Section: Introductionmentioning

confidence: 99%

“…In industrial praxis these electromagnetic forces are mostly taken into account without considering electromagnetic field damping. Electromagnetic field damping of induction motors is basically described in , but not integrated into a whole, analytical rotordynamic model. In neither stiffness/damping of bearings (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Electromagnetic field damping of induction motors is basically described in , but not integrated into a whole, analytical rotordynamic model. In neither stiffness/damping of bearings (e.g. oil film stiffness and damping of sleeve bearings), nor stiffness/damping of the support, nor excitation due to bent rotor deflection or magnetic eccentricity is there considered in conjunction with electromagnetic field damping.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Influence of electromagnetic field damping on forced vibrations of induction rotors caused by dynamic rotor eccentricity

2016

Z Angew Math Mech

The paper shows an analytical rotordynamic model for induction rotors, supported in sleeve bearings, especially focusing on the influence of electromagnetic field damping on the forced rotor vibrations. The analytical model contains electromagnetic forces in respect of electromagnetic field damping, stiffness and internal material damping of the rotor, typical dynamic eccentricities of an induction rotor -mass eccentricity, bent rotor deflection and magnetic eccentricity -, stiffness and damping of the support, and stiffness and damping of the oil film of the sleeve bearings. With this rotordynamic model a useful possibility is shown, how to consider electromagnetic field damping, when analyzing forced vibrations caused by dynamic eccentricities. The aim of the paper is to show a method -based on a simple rotor dynamic modelhow to consider electromagnetic field damping, which can also be adopted in Finite-Element-Analysis.

State space model for vibration control with arbitrary controller structures for soft mounted induction motors with sleeve bearings fixed on active motor foot mounts

2019

Z Angew Math Mech

In the paper, a state space model for vibration control with arbitrary controller structures for soft mounted induction motors with sleeve bearings fixed on active motor foot mounts is shown. Besides the mathematical description of the forced vibrations caused by dynamic rotor eccentricity, a procedure is presented to derive the threshold of vibration stability. The challenge of the paper is the use of arbitrary controller structures with different feedback strategies – feedback of the motor feet displacements, velocities or accelerations – in combination with a special vibration system. This specialty is, that the stiffness and damping matrices depend on the rotor angular frequency Ω, which corresponds to the excitation angular frequency, when analyzing the forced vibration, and depend additionally on the natural angular frequency ωstab of the critical mode, when analyzing the threshold of stability. After the mathematical description is shown, a numerical example of a 2‐pole induction motor (power rating 2.4 MW) is presented, in which the threshold of stability is analyzed as well as the forced vibrations due to dynamic rotor eccentricity by investigating the bearing housing vibrations, the foundation vibrations and the actuator forces.