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Characterisation of Losses in Electrical Steel


The research project described in this report was carried out along three lines of activities:

1) production of non oriented electrical steels with a controlled microstructure and the preparation of samples,
3) qualification of the electrical steels using standard techniques as well as innovative techniques, developed within the project,
3) application of the electrical steels and the qualification methods to six rotating electrical machines.

In the first part, the effect of the basic material properties (microstructure, texture...) on the magnetic behaviour was studied. Thereto, a set of materials with controlled microstructure was produced covering a certain range of grain size, and subjected to extensive magnetic measurements. In addition, the effect of material handling was investigated. To this end samples were prepared using classical techniques, as well as techniques with negligible impact, starting from the same materials. These samples were subjected to intercomparative measurements.

Another part of the project was focussing on the development and application of innovative measurements and modelling techniques. An advanced qualification method was developed, resulting in a precise description of the magnetic response of the electrical steel, subjected to alternating field conditions with arbitrary wave form and frequency. The alloys were first subjected to quasi-static measurements of hysteresis loops. The material response was also modelled using the Preisach theory, in parallel with the measurements. Secondly, the structurally controlled alloys were subjected to measurements at higher frequencies. Sinusoidal as well as distorted waveforms were considered. Moreover, selected tests on the effect of applied stress on losses in the structurally controlled alloys were performed. Based on the magnetic qualification under alternating excitation conditions, a correlation was constructed between the material parameters defined in the macroscopic modelling and the microstructural parameters. For all material, the rotational losses determined versus peak induction and magnetisation frequency. Samples were also subjected and investigated, in order to give an interpretation of the relationship between alternating and two-dimensional power-losses. From a phenomenological viewpoint, a correlation matrix for the ratio between the rotational and the alternating losses was produced for the various tested alloys.

At last part was dealing with the application of the qualified materials on electrical machines. Thereto, two sets of three test machines were constructed using the same design and starting from precisely qualified materials. Once the stators were completed, pick up coils were mounted on the stator teeth for the first set of three machines. The evolution of the magnetic properties of the electrical steel was studied throughout the machine production process. The local fields and fluxes inside the test machines were determined using numerical computations (FE time stepping) and local measurements (pick up coils). Knowing the local excitation the material is subjected to, the local losses inside the six machines was determined. Finally, the joint contribution of the local losses was compared with the global losses, measured on the test machines.

Three types of partners were participating in the project, i.e. steel producers (CSM/AST, OCAS/Sidmar and Ugine), research labs (ELMAPE, IENGF and POLITO) and the electric utility EdF. The steel producers, focussed on the production of materials with controlled microstructure, influence of mechanical handling on the magnetic properties asdn monitoring the changement of the material quality throughout the process of machine construction. The research labs were concentrating on the development of the magnetic qualification methods, while EdF was concentrating on the application to real machines. During the project an advanced technology has been developed based on the statistical loss theory and the Preisach theory to evaluate the iron losses in rotating electrical machines. The correlation between the microstructure of electrical steels and the macroscopic behaviour has been studied as well as the influence of the machine construction process material properties.

Objectives and content
The general objective of the project CHARLES is to establish the link between the material properties of electrical steel, and the losses occuring in electrical machines. To achieve this objective, the project will focus on the advanced magnetic qualification of various steel qualities. The advanced magnetic qualification will be based on state-of-the-art techniques in modelling (such as Preisach) and measurement (such as rotational loss measurements). The advanced magnetic qualification will be brought into relation with the material properties on the one hand, and with the real excitation conditions occurring inside the machines, on the other hand.
To establish the link between the material properties of the electric steel, and its magnetic qualification, a set of non-oriented materials with controlled microstructure will be produced, and
subjected to a detailed microstructural and magnetic qualification. In addition, the effect of material handling (punching) on the magnetic qualification will be investigated.
To establish the link between the magnetic qualification of the electrical steel, and the resulting losses occurring in machines, a set of test machines will be constructed from well identified materials. These materials will be magnetically qualified throughout the process of machine construction. In addition, the local fields in the machines will be determined through computations and local measurements, to identify the local excitation conditions inside the machines. Samples of the electrical steel will be submitted to these excitation conditions, to assess the local losses inside the machine. The sum of these local losses will then be compared with total losses, measured on the test machines.
Finally, the relation between the material properties of the electrical steel and the losses occurring. In electrical machines will be established. Based on this knowledge, a set of materials will be selected from all materials available within the project, and will be used to produce an additional set of test machines. Starting form the precise characterisation of the properties of these materials and from the qualification techniques developed within the project, the losses in the test machines will be predicted. The predicted values of the losses will be compared with the losses measured on the machines, thereby assessing the general objective of the project CHARLES.

Funding Scheme

CSC - Cost-sharing contracts


Universiteit Gent
9,Technologiepark-zwijnaarde 9
9052 Zwijnaarde

Participants (6)

Centro Sviluppo Materiali SpA
Viale Benedetto Brin 218/102
05100 Terni
Les Renardieres
77818 Moret Sur Loing
Corso Massimo D'azeglio 42
10125 Torino
3,John Kennedylaan 3
9060 Zelzate
Corso Duca Degli Abruzzi 24
10129 Torino
Ugine SA

62330 Isbergues