Finite Element Analysis (FEA) of Local Hyperthermia on Soft Tissue

Finite Element Analysis (FEA) is a method for simulating a local hyperthermia (HT) effect on the soft tissue liver by exposing it to an external heat higher than normal core body temperature. Local HT treatments are most commonly used to treat cancer tissue smaller than 3 cm in size by using radiofrequency ablation (RFA) technique. The radiofrequency probe provides an intense external heat source within the target zone with temperatures exceeding 50 °C, but its maximum temperature should not approach 100 °C. In this paper, the main idea is to study the effect of tumor diameter size on the exposure time, thermal exposure intensity and applied voltage. There are five (5) different tumor diameter tissue sizes that would be treated: 1 cm, 1.5 cm, and 2 cm of tumor tissue diameter treated with a monopolar of plain electrode, and 2 cm, 2.5 cm, and 3 cm of tumor diameter tissue treated with 4-prong retractable antennas of an electrode. The findings showed that the exposure time is influenced by the tumor diameter tissue and the voltage applied, with the bigger tumor diameter tissue necessitating the longest time exposure with a high voltage. The temperature range of 50-100 °C has been given by all of the voltage supplied. Both electrodes provide thermal damage between 6-20 minutes, which is 6 – 18.5 minutes for a plain electrode with a voltage supply of 20-35 V applied to 1cm, 1.5cm and 2 cm of tumor diameter tissue, and 10.5 – 12.5 minutes for a 4-prongs electrode with a voltage supply of 22-45 V applied to 2 cm, 2.5 cm and 3 cm of tumor tissue.

Accounting for Slot Harmonics and Nonsinusoidal Unbalanced Voltage Supply in High-Speed Solid-Rotor Induction Motor Using Complex Multi-Harmonic Finite Element Analysis

Solid rotor induction machines are still used in high-speed systems. A two-dimensional field-circuit model based on the finite element method and the complex magnetic vector potential has been shown as a very time-effective tool in the analysis of their steady states compared to time-domain models. This continuation work presents a validated computational algorithm that enables the inclusion of the nonsinusoidal and/or asymmetrical voltage supply in the multi-harmonic field-circuit model of these machines that was presented in the previous works by the authors. The extended model accounts for both spatial harmonics due to slotting and/or winding distribution and the time-harmonics due to voltage waveform. The applicability range of the model therefore increases to cases when the machine is supplied with a nonsinusoidal three-phase system of voltages with symmetry or asymmetry that can be decomposed into three symmetrical components. Its short execution time characteristic allows for much more insightful design studies of the contribution of voltage supply- and slotting-related harmonics to the overall efficiency of the machine than is possible with the time-consuming time-domain models. The proposed computational framework has never been presented in the literature. The model is verified positively by the comprehensive time-domain model. It is especially useful in design studies on solid rotor induction motors related to the optimisation of the efficiency of induction motor-based drive systems.

Multiple three-phase induction motors connected to a zigzag transformer

Many experiments have been conducted in this research work which is (i) connecting a zigzag transformer with an induction motor, (ii) connecting a zigzag transformer with multiple induction motors, and (iii) connecting multiple zigzag transformers with multiple induction motors. These experiments provide a thorough understanding of the sequence network connections under the single-phasing condition of a three-phase induction motor. Moreover, these experiments protect the three-phase induction motors from unbalancing voltage supply and allow the induction motor to start under unbalance voltage supply. Additionally, they keep the three-phase induction motor running even any one of the three phases disconnected from the power supply without creating excessive heat in the motor winding.