Vytautas Bleizgys

SVPWM method with the averaged pulse length versus conventional modulation method

The efficiency of the AC induction motor used in the variable speed drive fed by the three-phase AC voltage formed using developed by authors Space Vector Pulse Width Modulation (SVPWM) method with the averaged pulse length has been investigated. The obtained results are compared with the results gained using a conventional SVPWM method. They show that the SVPWM method with the averaged pulse length provides higher motor efficiency as compared to the case when a conventional SVPWM method is employed.

Compact high-sensitivity potentiometer for detection of low ion concentrations in liquids

The compact potentiometer, based on an electronic circuit protected from electrostatic and electromagnetic interference, was developed for the measurement of low ion concentrations in liquids. The electronic circuit of the potentiometer, consisting of analogous and digital parts, enables the measurement of fA currents. This makes it possible to perform reliable measurements of ion concentrations in liquids that are as small as 10-8-10-7M. The instrument was tested using electrodes that were selective for tetraphenylphosphonium (TPP+) ions. It was demonstrated that the characteristic response time of the potentiometer electronic circuit to changes in the concentration of these ions in a liquid was in the order of 10 s. An investigation of TPP+ absorption by baker yeast has shown that this device can be successfully used for long term (several hours) measurements with zero signal drift, which was about 1 μV/s. Finally, due to the small dimensions of the electronic circuit (7.5 × 2 × 1.5 cm), this potentiometer can be easily installed at a large apparatus in the laboratory condition (≈25 °C), such as high pulsed electrical generators of magnetic fields that are used in electroporation studies of biological cells.

Single phase cascaded inverter for renewable energy supplies

In this paper, the control technique for 2-Unit H- bridge inverter operation at high power rating is proposed. The technique provides 7 level voltages waveform, therefore, lower THD could be achieved. Employment of 2-Unit H-bridge inverter in power supply applications allows flexible load distribution among inverter legs. The proposed inverter control technique has been validated employing Matlab/Simulink test bench.

Electroporation system generating wide range square-wave pulses for biological applications

The design of a wide range square-wave pulse electroporation system is presented. The system is able to generate pulses having voltage amplitudes up to 4000 V and currents up to 100 A. The quantity of accumulated energy is optimized by the use of the variable capacitor bank. The proposed device has an integrated graphic LCD and measurement modules for current pulse visualization, and does not require an external oscilloscope. The whole system was tested with suspension of human lymphoma cells of Jurkat line in RPMI medium under a variety of electroporation conditions.

The Influence of Supply Voltage Amplitude Variation Law on AC Induction Motor Efficiency in Variable-Speed Drive

This paper presents investigation results of the influence of the supply voltage amplitude variation law on the efficiency of AC induction motor in variable-speed drive based on the frequency converter. It is demonstrated that the commonly employed linear and square voltage amplitude variation laws do not provide the highest efficiency of the AC induction motor. The corrected AC voltage amplitude variation dependences for different motor load torque, at which high efficiency of the motor supplied by the frequency converter is maintained, are proposed and discussed. Reported experimental study was performed on a special test bench.