Characterization of the local electrical properties of electrical machine parts with non-trivial geometry

Abstract

In electrical machines, knowing the electrical conductivity is of importance for the eddy current calculation, especially when massive iron parts are involved. Generally the conductivity is measured on samples of raw materials with simple geometries. Indeed, a simple geometry is suitable for applying an analytical approach to deduce the electrical conductivity from the measured electrical quantities. Nevertheless, when a non destructive measurement is required, the measurement of the electrical conductivity can become rather difficult on parts with complex geometry. To that end, with the help of the Finite Element Modeling approach (FEM), a strategy is developed to characterize the local electrical properties of parts with a non-trivial geometry.

Development and validation of an electrical and magnetic characterization device for massive parallelepiped specimens

“…The electrical conductivity measurement is based on the four-point method [4]. The four needles are arranged on a straight line with 6 mm equidistant spacing, the current is imposed flowing through the outer pair of needles and the voltage is measured between the two inner needles (Figure 2).…”

Magnetic ageing investigation of bulk low-carbon silicon steel

“…Regarding the electrical conductivity, the four-point method is employed [16]. In the configuration with a sensor having four aligned needles, a DC current is imposed between the outer pair of needles and the voltage is measured between the inner needles.…”

Characterization of the Local Incremental Permeability of a Ferromagnetic Plate Based on a Four Needles Technique

“…For the experimental part, the developed sensor is based on the principle of the four-point method proposed by Valdes in 1954 [9]. In a previous work this approach was used to measure the electrical conductivity of electrical parts with a non-trivial geometry [10]. To measure the electrical conductivity, a DC current is imposed between the outer pair of points and a voltage is measured between the inner points (Fig.…”

“…To perform this operation, it is necessary to know the thickness and conductivity of the studied sample. Then, for fixed thickness (T=2 mm), fixed conductivity which can be measured with a DC method [10] (σ=5,5MS/m) and different values of the relative permeability µ r , the numerical results are used to calculate the real and imaginary voltages (U r and U i ) versus the frequency of the AC current flowing through the external needles of the sensor (Fig. 12).…”

“…Both studied samples have a thickness T=2 mm and a conductivity σ=5.5 MS/m. The conductivity of the material has been determined by the method presented in [10] which is based on four needle technic supplied by a DC voltage coupled with the FE model. From the same experimental device and FE model the conductivity and the incremental permeability can be determined.…”