Ileana Torac

A few aspects concerning the squirrel cage induction motors efficiency improvement

The paper investigates the possibility to improve the efficiency of the squirrel cage induction motors. One analyzes the variation of the machines efficiency depending on the relative torque. The considered low voltage three-phase motors are the existing ones, having the rated power between 0.55 kW and 37 kW and the number of poles 4 and 6 respectively. The paper deals with “no tool cost” or “low tool cost” solutions. It is proposed a solution for the induction machine efficiency improvement, at full and partial-load regime.

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.

Analytical model of the synchronous reluctance motor with axially laminated rotor for optimization purpose

The paper deals with the parameter estimation of the synchronous reluctance machine with axially laminated rotor. A general analytical solution for the air-gap flux density and for the magnetizing inductance estimation is proposed. The good correspondence of computing and measured inductances validates the proposed method.

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.

A new algorithm and device for absolute linear encoders dedicated to long distance applications

This paper proposes a new mathematical algorithm for linear absolute encoder for long distance applications (>100 m). The new algorithm uses a stronger codification method than the classical binary one. Moreover, the proposed implementation uses only four optical sensors which make the method economically efficient. The algorithm and the proposed encoder where tested on an experimental setup. Design of the setup assures the control of all relevant parameters. Experimental results also allow the improvement of the initial algorithm by evolving from binary algebra to the polyvalent algebra (Lukasiewicz- Moisil algebra), using colors coding and color optical sensors.

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.

Closed slot induction machine inductances and rotor resistance characterization versus current and frequency via FEM

The paper presents the inductances and rotor resistance estimation - using FEM - for the closed slot induction machine. One presents the variations of inductances and rotor resistance as function on current and frequency for emphasizing their dependence upon the saturation level of the machine. So it is possible to estimate the machine parameters for a large area of the operating modes.

A few aspects about the squirrel cage induction motors in variable speed drives

The paper deals with standard three phase low voltage squirrel cage motors in variable speed drives. The aim is to investigate the possibility of improving the machines parameters at low speed. The considered industrial motors are the existing ones, having the rated power between 0.55 kW and 37 kW and 4 and 6 pole. The paper presents also an example emphasizing the possibility of improving the machine parameters using a “low tool cost” solution.

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.

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.