In this work, a miniaturized Y-sphere coupled photoacoustic (YSCPA) sensor is proposed for trace C₂H₂ gas detection. The cavity volume of the designed YSCPA sensor is about 0.7 mL. The finite element method (FEM) has been performed to analyze the comparative performance of the YSCPA sensor and T-type PA sensor, indicating that the first-order resonance frequency (FORF) of the newly proposed YSCPA sensor has been reduced by half while the PA signal has been improved by a factor of 3 compared to the T-type PA sensor. C₂H₂ is employed as a target gas to test the performance of the YSCPA sensor. The experimental test results show that the response time of the gas is 26 s. The minimum detection limit (MDL) reaches 189 ppb at a lock-in integration time of 1 s. By extending the lock-in integration time to 100 s, the MDL of the designed PA sensor is reduced to 18.1 ppb. The designed YSCPA sensor has the advantages of small size, low gas consumption, simple structure, and high sensitivity, which is expected to be an effective solution for rapid and real-time monitoring of dissolved C₂H₂ gas in transformer oil.

The tooth harmonics caused by stator slots are a major factor leading to low motor efficiency, high temperature rise and severe vibration. The application of a magnetic slot wedge (MSW) can effectively mitigate the adverse effects of the stator slot on the motor. However, it should also be noted that the MSW may be subject to the action of electromagnetic forces during motor operation and thus has a risk of falling off. In order to comprehensively analyze the impact of MSW on the electromagnetic and reliability performance of the motor, this paper selected three types of MSW with relative permeabilities of 5, 10 and 15 to be applied in a high-power line-start permanent magnet synchronous motor (LSPMSM). The effects of these three types of MSWs on the electromagnetic performance of the motor and the changes in the electromagnetic force acting on the MSW were studied. Finally, the research content of the paper was verified on a 630 kW, 6 kV, 4-pole LSPMSM, providing a reference for the selection and application of MSW in motors.