# Application of a multiobjective minimization technique for reducing the torque ripple in permanent-magnet motors

## Abstract

The demand for high performance permanent-magnet (PM) motors is continuously increasing in industrial applications because of their high efficiency and power density. The main design parameters of a permanent-magnet motor, which reduce the total torque ripple, are determined. A two-step design procedure is utilized. First the geometry of the permanent-magnet rotor is derived by a one-dimensional field analysis coupled to a multiobjective minimization technique. The objective function of the minimization is defined as a combination of the electromotive force harmonic components induced in the stator and of the harmonic components of the air-gap magnet permeance. As a second step, a two-dimensional numerical model, solved through a finite element method, is adopted to further improve the analysis of the magnetic field. This allows the optimization of the magnet arc width and the minimization of the cogging torque. The method described has been used for the design of a three-phase, six-pole, permanent-magnet synchronous motor. Experimental tests have been carried out to verify the results obtained by the design procedure.

- Authors:

- Publication Date:

- Research Org.:
- Univ. of Bologna (IT)

- OSTI Identifier:
- 20000593

- Resource Type:
- Journal Article

- Journal Name:
- IEEE Transactions on Magnetics (Institute of Electrical and Electronics Engineers)

- Additional Journal Information:
- Journal Volume: 35; Journal Issue: 5Pt3; Other Information: PBD: Sep 1999; Journal ID: ISSN 0018-9464

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; INDUSTRIAL PLANTS; ELECTRIC MOTORS; PERMANENT MAGNETS; PERFORMANCE; DESIGN; TORQUE; FINITE ELEMENT METHOD; COMPUTER-AIDED DESIGN; ALGORITHMS

### Citation Formats

```
Borghi, C.A., Casadei, D., Cristofolini, A., Fabbri, M., and Serra, G.
```*Application of a multiobjective minimization technique for reducing the torque ripple in permanent-magnet motors*. United States: N. p., 1999.
Web. doi:10.1109/20.799073.

```
Borghi, C.A., Casadei, D., Cristofolini, A., Fabbri, M., & Serra, G.
```*Application of a multiobjective minimization technique for reducing the torque ripple in permanent-magnet motors*. United States. doi:10.1109/20.799073.

```
Borghi, C.A., Casadei, D., Cristofolini, A., Fabbri, M., and Serra, G. Wed .
"Application of a multiobjective minimization technique for reducing the torque ripple in permanent-magnet motors". United States. doi:10.1109/20.799073.
```

```
@article{osti_20000593,
```

title = {Application of a multiobjective minimization technique for reducing the torque ripple in permanent-magnet motors},

author = {Borghi, C.A. and Casadei, D. and Cristofolini, A. and Fabbri, M. and Serra, G.},

abstractNote = {The demand for high performance permanent-magnet (PM) motors is continuously increasing in industrial applications because of their high efficiency and power density. The main design parameters of a permanent-magnet motor, which reduce the total torque ripple, are determined. A two-step design procedure is utilized. First the geometry of the permanent-magnet rotor is derived by a one-dimensional field analysis coupled to a multiobjective minimization technique. The objective function of the minimization is defined as a combination of the electromotive force harmonic components induced in the stator and of the harmonic components of the air-gap magnet permeance. As a second step, a two-dimensional numerical model, solved through a finite element method, is adopted to further improve the analysis of the magnetic field. This allows the optimization of the magnet arc width and the minimization of the cogging torque. The method described has been used for the design of a three-phase, six-pole, permanent-magnet synchronous motor. Experimental tests have been carried out to verify the results obtained by the design procedure.},

doi = {10.1109/20.799073},

journal = {IEEE Transactions on Magnetics (Institute of Electrical and Electronics Engineers)},

issn = {0018-9464},

number = 5Pt3,

volume = 35,

place = {United States},

year = {1999},

month = {9}

}