In this study, dichlorodifluoromethane (R12) gas and mixtures with nitrogen (N ₂ ) andair at different pressures and mixing ratios have been investigated and showedgood alternative to gas in terms of high‐voltage application.Mixed gases contain R12 gas, they offer good dielectric properties andpossibility to be used in low‐temperature environment. Synergistic effects andself‐recoverability test have been performed. Dielectric strength underquasi‐uniform field showed in the order of air in alternating current (AC), directcurrent (DC) and impulse was examined. Mixture R12/N ₂ (80/20%) couldreach over 0.90–0.95 times to that of gas at 50 lb/in ² at AC andR12/air (70/30%) gives 0.80–0.90 to gas. R12 gas presents brilliantself‐recoverability. The optimal ratio to switch gas is R12/N ₂ (80/20%) andR12/air (70/30%) is based on the authors’ experimental condition and setup.

Compared with the single rotor wind turbine, a counter-rotating (CR) wind turbine with two rotor sets leads to twice power density. In this regard, dual stator CR (DSCR) permanent magnet flux switching generator (DSCR-PMFSG) is employed. However, in DSCR-PMFSG both rotor and armature parts are rotating and require slip rings for power transmission. The slip rings associate demerits of constant maintenance, poor speed regulation, increased cost, and additional slip ring losses, whereas DSCR-PMFSG offer lower flux and lesser power density. To overcome the demerits as mentioned earlier of DSCR-PMFSG, this paper proposed a novel dual rotor counter-rotating permanent magnet flux switching generator (DRCR-PMFSG) for wind turbine applications that eliminate the requirements of slip rings and retain brushless operation. The proposed DRCR-PMFSG share one stator connected back-to-back through a flux bridge that provides an alternate flux path between two mechanical ports associated with the inner rotor and outer rotor, contributing to the cumulative output. A detailed comparative analysis of DSCR-PMFSG and DRCR-PMFSG is performed under static characteristics, overload, and wide speed range to generate output power, voltage, current, power density, and efficiency. Quantitative comparative analysis under static analysis evident that proposed DRCR-PMFSG exhibits 33.29% higher flux, suppressed cogging torque and torque ripples up to 53.48% and 67.45%, respectively. Furthermore, a comprehensive quantitative analysis is performed under coupled overload and over-speed capability. The analysis exposes that in comparison with DSCRP-PMFSG, the proposed DRCR-PMFSG improves voltage regulation factor by 55.88%, output current enhanced by 67.9%, raise output voltage to 2.01 times, and power density to 1.72 times while maintaining the efficiency of 90.195% and achieving stable voltage profile with load variation. Finally, a detailed comparative analysis with conventional designs is performed and comprehensive mathematical modelling based on sub-domain model is developed accounting stator slot and rotor pole combinations, magnetic saturation, and winding configuration to validates finite element analysis (FEA) utilizing JMAG Designer v.20.1.

This paper explains the state of art of switched flux wound-field machines (SFWFMs). The main advantage of these SFWFMs when compared with induction machines, synchronous machines, direct current machines, etc. is that all the active parts such that armature coil and field excitation coil are located on the stator while the rotor part consists of only iron material without windings. This makes the machine more robust, simple structure, and more suitable to be used for high-speed applications, compared to induction machine which has low mechanical strength, less torque desnity, and low power factor. Theories, numerical and technical literature of different SFWFM are described and analysed. Merits and demerits of different SFWFM structure are discussed. This paper categorized SFWFM topologies on the basis of their structure, flux linkage, cogging torque, average torque, and efficiency.

In this paper counter rotating (CR) dual rotor permanent magnet flux switching generator (CR-DRPMFSG) is designed and relatively studied with co-rotating DRPMFSG (CoR-DRPMFSG) for wind turbine applications. The developed CR-DRPMFSG and CoR-DRPMFSG share same stator linked with flux bridge which provide flux route. A comprehensive relative assessment of both CR-DRPMFSG and CoR-DRPMFSG are presented with static attributes, over-load, and over-speed capability for generating output voltage, output current, output power, power density, losses, and efficiency. Comparative study with static characteristics illustrates that developed CR-DRPMFSG shows 34.34% elevated phase flux which improve output power, cumulative output torque is improved by 23.86%, and suppressed cogging torque by 66.87% at CoR-DRPMFSG that results lower pulsation in instantaneous torque. Furthermore, a detailed performance analysis is investigated with different number of armature winding turns per phase and combined over-load and over-speed capability. Study discloses that in contrast with CoR-DRPMFSG counterpart CR-DRPMFSG offer 27.17% higher output power that results 1.25 times power density at a good voltage regulation factor of 18.67%. In additional, despite of 2.27% improvement of efficiency in case of turns analysis and 4.81% increase in overload and overspeed capability, contour efficiency map unveils that CR-DRPMFSG offer wide range of higher efficiency operating region during over-load and over-speed conditions accompany with stable voltage with the varying load profile.