Tomas Kavalir

Key construction aspects of resonant wireless low power transfer system

The paper discuses an important construction aspects of resonant wireless power transfer (WPT) system for small portable devices. It focuses mainly on key electrical parameters of the systems resonant linkage and its proper construction shape. All presented theoretical presumptions are consequently verified by detailed measurement.

Basic operating characteristics of wireless power transfer system for small portable devices

Recent research in wireless power transfer using resonant inductive coupling has made a significant progress and reached very high efficiency (usually above 85 %) at large distances. This paper offers a methodology for the basic analysis and prediction of efficiency of the wireless power transfer system for small portable devices. It also gives an overview of operating characteristics of the system for different positions of transmitting and receiving elements. All presented theoretical presumptions are consequently verified by detailed measurement.

Key construction aspects of low frequency wireless power transfer system using parallel resonance

The papers deals with the wireless power transfer (WPT) system using parallel resonance at low frequency. Two different construction arrangements of two-coil resonant system - with and without impedance conversion - are presented. Impedance conversion is carried out via linkage autotransformer. Both systems are consequently measured and the theoretical presumptions are verified.

Comparison of Vibration and Noise Measurement of Induction Machine Under Static Eccentricity

The paper is focused on the comparison of vibration and emitted noise measurement of induction machine under static eccentricity in an environment with steady acoustic noise producing facilities. Such an environment can introduce for example simple industrial drive stand operating under constant load in a closed room. The analyses are focused to the frequency spectrum up to 1500 Hz which allows us to validate the frequency spectrum of emitted noise by vibration measurement. The analyzed frequency band is sufficient considering vibration response of implemented fault. The analyses of healthy machine are carried on as well to get the reference point.

Minimization of Equivalent Series Resistance of Coupling Coils for Wireless Power Transfer Applications

The paper discusses analytical approach for calculation of equivalent series resistance of coupling coils applicable in wireless power transfer (WPT) systems. It gives an effective method to consider the proximity effect into the coil design and to find minimal possible value of its resulting serial resistance. The proposed approach uses simple linear equations to make the method intuitive and easily adopted. This may help designers to improve the transmitting efficiency of WPT systems due to lower I2R losses generated in windings.

Reduction of Pulsating Torque of the Synchronous Motor Using Magnetic Wedges

The paper analyzes the influence of magnetic wedges on the content of harmonic components in the induced voltage of the machine in the noload state and the pulse torque in the rated state to reduce the pulsation of torque on the rotor. The analysis is done using the finite element method and the model is designed using the symmetry of the machine. In total, four cases were compared and the results could be used for other proposed machines.

Natural frequencies of small squirrel cage induction machine rotor — Finite element model optimization

The paper deals with possibilities of geometry simplification for FE structural model calculating natural frequencies and mode shapes of rotor of small squirrel-cage induction motor. Proposed simplifications lead to the computing time savings while good result accuracy is preserved. All results are verified by experimental measurement.

Dynamic load of induction machine due to rotor's eccentricity and bearing clearance

The most critical part of the induction machines which determines on their life time operation are rolling element bearings. To ensure reliable drive with an induction machine requires deep insight in electro-mechanical dynamics during its operation. The flexible multibody modeling technique enables the simulation of dynamic loads on all drive components. This paper focuses on complex dynamic modeling of machines behavior in case of eccentrically placed rotor supported by nonlinear bearing with radial clearance. The life time of machines bearing becomes very important issue of machines maintenance and reliability and is markedly influenced by any unbalanced forces acting on the rotor. Only the complex electro-mechanical models of the rotor considering all unbalanced electrical and mechanical rotor forces can provide the very detailed information about the bearing load. The methodology of determination of such loading is applied to the 11 kW squirrel-cage induction machine.