Which of the following contributes to better running torque in a single-phase motor?

A run capacitor significantly enhances the performance of a single-phase motor, particularly in terms of its running torque. When installed, the capacitor creates a phase shift in the current that allows the motor to develop a secondary magnetic field. This helps in providing additional starting and running torque, which is especially beneficial for applications requiring higher efficiency and better performance under load. The run capacitor also improves the overall power factor of the motor, allowing it to operate more efficiently.

In contrast, while higher voltage input could potentially increase power output, it doesn't specifically improve running torque in single-phase motors unless the motor is designed for higher voltages. Thicker wire gauge can reduce resistive losses, but it does not directly influence the torque characteristics of the motor running under typical load conditions. The use of an inverter is more relevant for speed control and variable frequency operations and does not directly contribute to improving the running torque of a standard single-phase motor. The most effective method for increasing running torque without altering the fundamental design of the motor is through the implementation of a run capacitor.