For high-power 2-4 pole motors, wind friction accounts for a considerable proportion, such as the wind friction of a 90kW 2-pole motor, which can reach about 30% of the total loss. Wind friction is mainly composed of the power consumed by the fan. Due to the generally low heat consumption of high-efficiency motors, the cooling air volume can be reduced, resulting in a reduction in ventilation power. The ventilation power is approximately proportional to the 4-5th power of the fan diameter, so reducing the fan size can effectively reduce wind friction when temperature rise permits. In addition, the reasonable design of ventilation structures is also important for improving ventilation efficiency and reducing wind friction. Experiments have shown that the high-power 2-pole wind friction loss of high-efficiency motors can be reduced by about 30% compared to ordinary motors. Due to the significant reduction in ventilation losses and the need for minimal additional costs, changing the fan design is often one of the main measures taken by these high-efficiency motors.
Reduce stray losses through design and process measures
The stray losses of asynchronous motors are mainly caused by high-frequency losses caused by high-order harmonics of the magnetic field in the stator and rotor cores and windings. To reduce load stray losses, Y-Δ series connected sine windings or other low harmonic windings can be used to reduce the amplitude of each phase band harmonic, thereby reducing stray losses. Experiments have shown that using sine windings can reduce stray losses by an average of over 30%.
Improve die-casting process to reduce rotor losses
By controlling the pressure, temperature, and gas emission path during aluminum casting of the rotor, the gas in the rotor guide bar is reduced, thereby improving conductivity and reducing aluminum consumption of the rotor. In recent years, the United States has successfully developed copper rotor die-casting equipment and corresponding processes, and is currently conducting small-scale trial production. Calculations show that if cast copper rotors are used instead of cast aluminum rotors, rotor losses can be reduced by approximately 38%.
Applying computer optimization design to reduce losses and improve efficiency
In addition to increasing materials, improving material performance, and improving processes, computer optimization design is adopted to reasonably determine various parameters while meeting constraints such as cost and performance, in order to achieve the maximum possible improvement in efficiency. Adopting optimized design can significantly shorten the time of motor design and improve the quality of motor design.