Thierry Coorevits

Influence of the stator deformation on the behaviour of a claw-pole generator

Imperfections of the manufacturing process can modify the shape of the electrical machine parts which dimensions are then not equal to the nominal ones. In this communication, the influence of three types of stator deformation is studied in the case of a synchronous claw pole machine with a non linear 3D finite element model accounting for the movement.

Optimization of the straightness measurements on rough surfaces by Monte Carlo simulation

The straightness error of a coordinate measuring machine (CMM) is determined by measuring a rule standard. Thanks to a reversal technique, the straightness uncertainty of the CMM is theoretically dissociated from the straightness uncertainty of the rule. However, stochastic variations of the whole measurement system involve uncertainties of the CMM straightness error. To quantify these uncertainties, different sources of stochastic variations are listed with their associated probability density functions. Then Monte Carlo methods are performed first to quantify error and secondly to optimize measurement protocol. It is shown that a 5-measurement distance from 0.1 mm to each measurement coordinate allows a double reduction of uncertainties, principally due to the rule roughness amplitude (R(a) = 0.35 µm) and because this optimal distance of 0.1 mm is equal to the autocorrelation length of the rule roughness. With this optimal configuration, the final uncertainly on the straightness error of the CMM studied is less than 1 µm on the whole evaluated length of the rule (1 m). An algorithm, including Probe Tip Radius of the CMM and surface roughness of the piece, is finally proposed to increase CMM reliability by minimizing error measurements due to surface roughness of the measured piece.

Estimation of the constitutive law by dual Small Punch Test and Instrumented Indentation

In this paper an inverse finite element procedure was developed to assess the true- stress strain relationship of a DP dual phase. Experiments were performed both by means of instrumented indentation and small punch tests on small samples cut in the same steel sheet. Tests are developed on a Zwick macro-hardness tester. Single test are first proposed in order to estimate the parameters of the constitutive law (K,n). We propose to conduct SPT tests using PTFE lubricant and hard (WC / Co) ball. An inverse method based on the Nelder and Mead algorithm has been developed in order to found experimental curves. Nevertheless we show that this method lead to poor estimation of the parameter of the constitutive law. We propose to improve these estimations by cross-mechanical tests. Indeed we show that the estimation of the low-error (K,n) domains deduced from each single test can be crossed. This method leads to a better estimation of the constitutive law. Moreover both load/displacement curves of SPT and macrohardness can be found again.

Influence of the manufacturing process of a claw-pole alternator on its stator shape and acoustic noise

This paper shows the influence of the manufacturing process of a claw-pole alternator on its acoustic noise. First, the stator welds and the assembly of the stator in the brackets are linked to deformations of the inner diameter of the stator. Then, the influences of these deformations on the magnetic forces and the subsequent acoustic noise are investigated. Results show that the deformations caused by the manufacturing process significantly increase the sound power level of particular orders.

Study of the Influence of the Fabrication Process Imperfections on the Performance of a Claw Pole Synchronous Machine Using a Stochastic Approach

In mass production, fabrication processes of electrical machines are not perfectly repeatable with time, leading to dispersions on the dimensions which are not equal to their nominal values. The issue is then to link the dispersions on the dimensions, which are uncertain to the performance of electrical machines in order to evaluate their influence. To deal with uncertainty, there is a growing interest in the stochastic approach, which consists of modeling the uncertain parameters with random variables. In fact, this approach enables us to quantify the influence of the variability of the uncertain parameters on the variability of the quantities of interest. In this paper, a stochastic approach coupled with a 3-D finite-element model is used to study the influence of the fabrication process imperfections, such as the rotor eccentricity and the stator deformation, on the performance of a claw pole synchronous machine.