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Objective: The use of multiple-stage cycloconverters is suitable for variable-frequency speed control of high-voltage, large-capacity motors, for which it is sometimes necessary to establish separate controls for variable-frequency operation and the start-up phase. This approach effectively limits the starting current of the large-capacity motor by switching the phase relationship of the triple circuit’s output voltages to control the overall output voltage. Methods: We analyze a triple circuit using voltage vector analysis and simulation analysis with MATLAB modeling. Results: We find that our triple soft-start control strategy can be applied to large-capacity motors, as this strategy results in a pure sine wave output voltage and current, and maintains balance in the three-phase voltage during startup. Conclusion: In order to further decrease these types of effects, we will conduct more research on a cycloconverter that has six stages of the converter circuit, rather than the three stages mentioned before. Furthermore, the sextuple cycloconverter, which can be used to practically drive high capacity pumps or fans, will be developed by combining the “phase hopping” method and the soft-start method mentioned in this paper.

This study proposes a new AC/AC "phase hopping" frequency conversion method based on the analyses of the disadvantages of the conventional cosine wave-crossing method. The advantages of this new method include no circulating current, no dead time, and an output frequency close to the power frequency. This study also introduces the basic principles of the "phase hopping" method and analyzes these principles combined with the voltage phase-changing comparison to that of the cosine wave-crossing method. The "phase hopping" principles are used to analyze the generation of thyristor trigger pulses, including the generation time and duration. A simulation is conducted in MATLAB, and the simulation output waveform and harmonic analysis results are then obtained. The proposed approach is verified on an experimental platform. Consequently, the results are in good agreement with those of the theoretical and simulation analyses.

The dynamic threshold algorithm (DTA) presented by Pan Tompkins is a popular QRS detection method, and it has high sensitivity and specificity. However, the accuracy of this algorithm would be compromised if its sensitivity is increased. In this study, an enhanced dynamic threshold algorithm (EDTA) based on dynamic threshold rules is proposed, which add a compensation scheme to reduce the rate of misdetection and missed detection of R wave in low signal-to-noise ratio condition, sensitivity and detection error rate are calculated on simulated and clinical data to compare the performance between EDTA and DTA, and EDTA yields a competitive results. For the clinical data, the average accuracy rate of EDTA is 99.24%, which is higher than that of DTA at 95.98%. Further compared experiments among EDTA and the two other popular algorithms are conducted and the results of their validation over a public database are given and discussed, which prove our superiority.