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Attentive netizens will notice that when we look at products such as refrigerators, air conditioners, or washing machines, we can see the keyword “variable frequency” in their titles. Of course, the variable frequency mentioned here refers to variable frequency motors. So, compared to the motors used in household appliances of the past, what are the characteristics of variable frequency motors? What special experiences can it bring us? Let’s explore it together. More energy-efficient: All household appliances generate harmonic voltages and currents to varying degrees during motor operation, causing the motors to run under non-sinusoidal voltage and current conditions. Higher harmonics cause an increase in the copper loss in the motor stator, the copper (aluminum) loss in the rotor, the iron loss, and additional losses, with the copper (aluminum) loss in the rotor being the most significant. Since a conventional AC asynchronous motor rotates at a synchronous speed corresponding to the fundamental frequency, high-order harmonic voltages, when cutting across the rotor bars with a large slip, cause significant rotor losses. In addition, the additional copper loss caused by the skin effect must also be taken into account. All these losses cause the motor to generate extra heat, resulting in reduced efficiency and lower output power. However, by using an inverter-driven motor, energy consumption can be reduced by about 20%-30%. Long service life: When the motor is in operation, the carrier frequency ranges from a few thousand to over ten thousand hertz. This results in the stator windings of the motor having to withstand very high voltage spikes, which is equivalent to applying a shock voltage with a high gradient to the motor, placing severe stress on the inter-turn insulation of the motor. Variable-frequency motors can operate at voltages below those provided by rectification and filtering, resulting in more stable performance and a longer lifespan. Low noise: Ordinary asynchronous motors experience more complex vibrations and noises due to factors such as electromagnetic effects, mechanical issues, and ventilation. The various temporal harmonics present in the variable-frequency power supply interact with the inherent spatial harmonics of the electromagnetic components of the motor, resulting in various electromagnetic excitation forces. When the frequency of the electromagnetic force wave matches or is close to the natural vibration frequency of the motor body, resonance occurs, thereby increasing noise. Due to the wide operating frequency range of electric motors and the large variation in rotational speed, it is difficult to avoid the natural vibration frequencies of the motor’s various components for various electromagnetic force waves. However, variable-frequency motors can effectively solve these problems.