May 2018 EOMYS newsletter: Automatic FRF in Ansys/Optistruct, Experimental testbench, notches in DCM

FRF with structural FEA software

The automated coupling between MANATEE and Ansys Mechanical (similar to the coupling with Altair Hypermesh/Optistruct) has been finalized. The coupling enables to build from MANATEE the orthotropic stator lamination subject to (clamped/free) boundary conditions, and to apply automatically the most relevant magnetic rotating excitations according to the Electromagnetic Vibration Synthesis algorithm. An automated validation case sucessfully compares the Frequency Response Function obtained with Optistruct, Ansys and MANATEE’s analytical model:

MANATEE FRF validation

This validation shows that MANATEE’s analytical model successfully captures the main structural dynamics of a stator under magnetic excitations with significant time reduction compared to FEA (10000 times faster).

Experimental testbench

EOMYS is currently developing an experimental testbench to demonstrate the phenomenon of electromagnetic noise and vibrations and to benchmark the differences between simulation methods with experimental data. A 12 stator slots with 5 pole pairs Surface Permanent Magnet Machine has been chosen to study slotting modulation and tangential force effects. The rotor is driven by a magnetic coupling to minimize the effect of the loading machine and the frame allows to easily change the stator in order to study slot/pole combination effects.

EOMYS testbench with 12s10p IPMSM (without stator)

All the experimental data of the testbench measured by EOMYS will be shared.

Ongoing MANATEE developments

  • The order tracking analysis has been extended to velocity and acceleration.
  • A windowing signal processing now enables to obtain more reliable spectrograms at variable speed, in particular in case of Pulse Width Modulation excitations.
  • A user-defined magnetization curve can now be imposed in subdomain models to study the effect of uneven magnetization, uneven pole position and rotor non circularities on noise and vibrations.

Conferences and Events

EOMYS makes a presentation on 21th June, University of Coventry (UK), during a seminar entitled "Electric Vehicle NVH: Not as quiet as you thought?". The presentation of EOMYS deals with Electromagnetically-excited Noise Mitigation Techniques of Electric Motors Used in EV/ HEV Traction Application.

Publication of the month

The publication work of the month is:

Y. B. Li, S. L. Ho, W. N. Fu and B. F. Xue, "Analysis and Solution on Squeak Noise of Small Permanent-Magnet DC Brush Motors in Variable Speed Applications," in IEEE Transactions on Magnetics, vol. 45, no. 10, pp. 4752-4755, Oct. 2009.

In this publication the noise due to electromagnetic excitation of a DC motor is studied and reduced using rotor notches.

The driving noise mechanism is the Unbalanced Magnetic Pull due to GCD(Zs,2p)=GCD(3,2)=1, creating a wavenumber r=1 in the machine. When introducing 3 additional "dummy slots" or notches, the number of stator slots is artificially increased to 6, giving GCD(Zs,2p)=GCD(6,2)=2. The Unbalanced Magnetic Pull is therefore cancelled. This type of noise control action including notch shape optimization can be efficiently implemented in MANATEE software.

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