Javad Fouladgar

A statistical approach of temperature calculation in electrical machines

The thermal behavior of electrical machines is studied. The finite element method is used to calculate the magnetic field and temperature distribution inside the machine. The conductors are randomly distributed inside the slots using the Monte-Carlo method. The random distribution of the maximum temperature of the windings is calculated and its limits of confidence are evaluated.

Microscopic and macroscopic electromagnetic and thermal modeling of Carbon Fiber Reinforced Polymer Composites

An electromagnetic and thermal model of carbon fiber reinforced polymer composite material is introduced. This model takes into account the influence of different fiber orientations on the electromagnetic parameters. These parameters are defined in microscopic scale and introduced in finite-element-method model in macroscopic scale.

3-D Simulation of induction heating of anisotropic composite materials

This paper presents a three-dimensional modeling of induction heating of conductive composite materials using the shell elements. These elements are generalized by taking into account the anisotropic behavior of the load. Magnetic fields and temperatures on the composite load are then calculated and compared with experimental measurements.

3-D computation of transformers overheating under nonlinear loads

This paper deals with a mixed analytical and numerical method to study the electromagnetic and thermal behavior of a dry type transformer under nonlinear loads. First a three-dimensional finite element method (FEM) using a magnetic scalar potential formulation is applied to compute the magnetic field in the free and iron spaces. This nonlinear FEM calculation is then combined with a mixed analytical and numerical form of the electrical circuit equation to take into account the skin and proximity effects in the rectangular windings. Then a steady state thermal FEM using the previous resultant current densities allows to characterize the temperature distribution of the transformer with nonsinusoidal currents. Finally this coupling model is applied to a 10-kVA distribution transformer to validate the effectiveness of the proposed method.

A magneto-thermal study of a high-speed synchronous reluctance machine

The paper presents a magneto-thermal model of a high-speed synchronous reluctance machine (SRM). Both magnetic and thermal aspects are described using two-dimensional and three-dimensional finite-element method for machine modeling. Additional current harmonics losses, friction losses, and convective exchange coefficients at high speed are estimated. Finally, test results on a 20kW, 20 000rpm SRM are reported and compared with the simulation results

The influence of the harmonics on the temperature of electrical Machines

In this paper, we study the temperature rise in an asynchronous motor with nonsinusoidal voltage feeding. The stator and rotor current harmonics are calculated using a time step method. Inverse problem techniques are used to evaluate the homogenized electromagnetic and thermal characteristics of the stator windings. Temperatures in sinusoidal approximation and harmonic currents are compared with experimental measurements.

Determination of the Electrical Conductivity Tensor of a CFRP Composite Using a 3-D Percolation Model

In this paper a percolation model is used to determinate the electrical conductivity tensor of one layer of carbon fiber composite. For this kind of material, fibers are randomly distributed in the resin. To take into account this distribution a virtual 3-D material model is developed and coupled with a homogenization method to overcome the scale factor problem. The electrical conductivity tensor is then used to simulate the induction heating of a multilayer composite.

Electromagnetic and thermal behaviors of multilayer anisotropic composite materials

A methodology based on shell elements, to study the electromagnetic and thermal behavior of multilayered anisotropic conductive composite materials, is presented. The anisotropic behavior and orientation of each layer of the composite material has been taken into account. The model is validated with experimental results. It is then applied to study the induction heating of composite materials, and also to detect the delamination in these materials

3-D Numerical Modeling of the Thermo-Inductive Technique Using Shell Elements

Thermo-inductive testing is a new technique used for health investigations on different components of automotive and aeronautic industries. In this technique, eddy current deviation around the default creates local heating which can be detected by an infrared camera. The purpose of this work is to develop a 3-D finite-element model as a support tool to study the reliability of the technique. To reduce the number of unknowns, shell elements are introduced to model defects or thin conductive regions. Inspected materials are classified into metallic and composites. Investigations on various parameters of the technique and crack dimensions are performed in order to optimize the method. Experimental and simulation results show that the method is well suited.

Asymptotic calculation of equivalent electromagnetic and thermal properties for composite materials

In this paper, the asymptotic development method is used to study the electromagnetic and thermal behavior of nonhomogeneous materials. The method, widely used in high frequency applications, is adapted to an induction heating system of partially conducting composites. The asymptotic method, based on the spatial filtering of the electromagnetic field, is applied to study the composite materials with periodic structure. The model is valid when the size of the elementary cell is small compared with the dimensions of the system. For large cells, the model gives an average value of field. A local solution is then used to improve the homogenized field. The conditions of using the model for nonperiodic structures are also discussed.