Rotordynamics and Machine Optimization

Ensure high performance and stability from your magnetic bearing system.
To get maximum performance and stability from a magnetic bearings system, rotordynamics - the dynamic motion of the rotating shaft - is critical. Synchrony® rotordynamics specialists work closely with OEMs to develop numerical models to ensure that your machine is stable and performs up to specifications.

The optimization process is quick and easy, because the integrated development environment allows the engineer to change control parameters and instantaneously measure the closed-loop and open-loop transfer functions via a graphical HMI. These measurements can also be taken while the shaft is rotating to ensure stability at various speeds. It's another facet of Synchrony's commitment to total support and to added value for our NovaGlide™ and Fusion® magnetic bearing solutions.

Numerical Modeling

The rotordynamic analysis and machine optimization begins with developing a detailed numerical model for the machine structure (rotating assembly and static structure if necessary). Synchrony models accurately represent how our magnetic bearings perform, and by integrating these models with the model of the machine, the complete system is dynamically analyzed, including:

  • Eigen value analysis to ensure all system modes are stable
  • Mode shape analysis to ensure proper positioning of nodes relative to bearings, and to ensure that the relative displacements at the anti-nodes are acceptable
  • Unbalance analysis to ensure unbalance forces are within bearing design limits, and that amplification factors and displacements are within acceptable limits
  • Campbell plots to quantify the effect of gyroscopic forces on rotordynamic behavior over a range of rotational speeds.
Machine Testing

Magnetic bearings are tested in the machine as the last step in the optimization process. The numerical modeling of the shaft and the performance of the bearing are validated by measuring the closed-loop transfer function. Shaft response is measured over a range of frequencies (e.g., 0-2000 Hz). If the response of the system is different from the prediction, the numerical model is adjusted and control parameters to the bearing are re-optimized.

Because the final optimization involves closed-loop measurements without the need for external instrumentation (through the user interface), Synchrony can typically complete the final optimization in less than six hours for a new machine. During a closed-loop measurement, the shaft is excited by the magnetic bearing at a specific frequency and the response is measured by the integral position sensors. The measurements are performed automatically over a range of frequencies and the Eigen values (frequency and stability) are indentified. The frequency sweeps may in turn be performed over a range of rotational speeds to completely characterize the dynamics of the machine.

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