The use of frequency-controlled machines equipped with magnetic couplings is becoming increasingly widespread. The critical frequency range can now be defined up front with a new EagleBurgmann software tool, resulting in enhanced pump reliability.
Permanent magnets in the magnetic couplings transmit the torque. Hermetic sealing prevents leakage of the process medium. High-performance magnetic couplings are often the solution of choice if heating effects need to be minimized, for example when the medium is near the evaporation point. If the motor's operating point remains constant at asynchronous speed, no further measures are necessary because the operating point coincides with the design point. If however the pump manufacturer or user wishes to operate the pump at variable speeds, the high-performance magnetic coupling has to meet additional criteria. The special design of these couplings makes them highly efficient and minimizes eddy currents, but it also causes the segments to vibrate. The couplings should be designed right from the start to shift the natural frequencies and avoid resonance problems. That however is not possible in some applications. In these circumstances, critical frequencies have to be avoided during operation.
Time-consuming FEM analysis
The object of FEM analysis is to predict the dynamic behavior of the high-performance magnetic coupling system. If the modeling of the physical geometry is accurate and the assumptions about the operating environment are correct, FEM analysis delivers very good natural frequency data for the application. However, generation of the geometric model and performance of the calculations are very time consuming. FE analysis also adds additional cost. To make the work more effective and less expensive, EagleBurgmann has developed a software tool which design engineers can use to calculate natural frequencies.
Quick and easy
The calculation methodology is based on the fundamental principles of continuum mechanics. Verification of the results is performed initially using the theoretical data. This is followed by analysis of measurement data collected at the high-performance magnetic coupling. Information on the frequency ranges or speeds to be avoided can be derived quickly and easily from the natural frequency data. These ranges must be passed through as quickly as possible to ensure safe, reliable pump operation even on frequency-controlled machines.
Conclusion: Safe, reliable pump operation has top priority from the user perspective. A new methodology for ensuring the dependability of frequency-controlled machines with high-performance magnetic couplings is now available. With this tool, the potential resonance range can be defined before the pump is put into operation.