Views: 7 Author: Site Editor Publish Time: 2025-09-23 Origin: Site
General use standard asynchronous motors are designed for constant frequency and constant voltage operation. They cannot fully meet the requirements of speed regulation by a variable-frequency drive (VFD), so they cannot be used as variable-frequency motors.
During operation, a VFD generates harmonic voltages and currents of varying degrees, which causes the General use standard asynchronous motor to run under non-sinusoidal voltage and current conditions. The high-order harmonics in this process will lead to an increase in the motor's stator copper loss, rotor copper loss, iron loss, and additional losses. Among these losses, the rotor copper loss is the most significant. These extra losses will make the motor produce more heat, resulting in reduced efficiency and decreased output power. Generally, the temperature rise of a General use standard asynchronous motor will increase by 10% to 20% in such cases.
When a General use standard asynchronous motor is powered by a VFD, the vibration and noise caused by factors like electromagnetism, mechanics, and ventilation will become more complex. The various harmonics contained in the variable-frequency power supply interact with the inherent spatial harmonics of the motor's electromagnetic components, forming a variety of electromagnetic exciting forces. These forces further amplify the noise of the motor. Moreover, since the General use standard asynchronous motor operates within a wide frequency range and has a large speed variation scope, it is quite difficult for the frequencies of various electromagnetic force waves to avoid the natural vibration frequencies of the motor's structural parts.
When the power supply frequency is low, the losses caused by high-order harmonics in the power supply will be relatively large. Secondly, when the speed of the General use standard asynchronous motor decreases, the cooling air flow will reduce in proportion to the cube of the speed. This reduction in cooling air flow makes it difficult for the heat generated by the motor to dissipate, leading to a sharp rise in temperature. Eventually, it becomes hard for the motor to achieve constant torque output.
