Toma Dordea

Analytical estimation of the Roebel bar losses

The paper presents an analytical method for the Roebel bar losses computation. The most general Roebel bar structure, including both solid and hollow elementary conductors was considered. Using the proposed method it was developed a computing program which estimates with a good accuracy the bar losses. One can analyze the influence of any input quantities (machine and material data) on the bar losses. So it is possible to optimize the Roebel bar structure for the machine efficiency improvement.

Modeling and simulation of AC machines behaviour in dynamic operation - critical analysis

In this paper, mathematical models of saturated AC machines are obtained by taking into account the dynamic variation of magnetic saturation. It is shown that various sets of state variables have a common theoretical background that simplifies the derivation of saturated models. Significant data are presented for comparative analysis of different ways to consider saturation in the dynamic operation of AC machines.

Roebel bar losses estimation for optimization purpose

The paper deals with the Roebel bar additional losses computation. One presents an analytical method for the estimation of the electric current in the elementary conductors, as function of the geometrical dimensions and material data, which provides a high accuracy of i2r losses calculus. The radial field in the slot area and that in the end coil area are taken in to account. The bar composed of both solid and hollow elementary conductors was considered. The computing program based on the proposed method allows the Roebel bar optimization. The paper presents two simulation results and a few parts of the experimental model for the validation of the proposed method.

Analytical estimation of the electric currents in the elementary conductors of a Roebel bar

The paper presents a method for the calculus of the currents in the elementary conductors and the additional winding losses for high power a.c. machines. The accuracy method estimation and the results for a hydro-generator of 216 MW validate the proposed method for the design of the Roebel bars.

Currents distribution analysis in nontransposed elementary conductors of a full-scale model bar

This paper deals with analysis of strand currents distribution in a model bar with non-transposed subconductors. The strand currents distribution are calculated with an analytical method (strips method) and are compared with the measured values using a full scale model bar test setup. The calculated results are close to the measured values of the strand currents and confirm the effectiveness of the strips method providing a good estimation of both strand currents and additional losses in winding bars (including Roebel bars) of high power electrical machines.

Simulation of dynamic operation in salient pole synchronous machines

The design of todays high performance synchronous motors must take into account not only the steady state but also practically inevitable dynamic regimes. In such conditions an accurate predetermination of the parameters and constructive solution by modeling and simulation of the given dynamic operation, becomes a mandatory step. In this aim, in the present paper a novel mathematical model of the high power salient pole synchronous machine (SPSM) is elaborated. We proposed to consider especially the effects of the magnetic saturation and saliency. The qualitative and quantitative results show an important number of valuable information in the design stage of the synchronous machine.

The current distribution on the elementary conductors of the Roebel bar

The paper deals with the Roebel bar losses computation. It was considered the most general Roebel bar structure, including both solid and hollow elementary conductors. One proposes an analytical method for the estimation of the currents in the elementary conductors, as function on the geometrical dimensions and material data. It is possible to emphasize also the current density distribution on the cross section of each elementary conductor. The radial field in the slot area and that in the end coil area were taken in to account. One can analyze the influence of any quantities (machine and material data) on the Roebel bar losses. Therefore, the proposed method is very useful to optimize the bar structure, for the machine efficiency improvement.