Why can't ordinary motors be used as variable frequency motors?

1. The carrier frequency of the frequency converter ranges from several thousand to tens of kilohertz, which causes the stator winding of the motor to withstand a high voltage rise rate, equivalent to applying a steep impulse voltage to the motor, causing the insulation between turns of the motor to withstand a more serious test.
When a regular motor is powered by a frequency converter, it will make the vibration and noise caused by electromagnetic, mechanical, ventilation and other factors more complex.
When the power frequency is low, the losses caused by high-order harmonics in the power supply are greater. Secondly, when the speed of the variable motor decreases, the cooling air volume decreases proportionally to the third power of the speed, causing the motor heat to not dissipate and the temperature rise to increase sharply, making it difficult to achieve constant torque output.

The main issue is heat dissipation, with a dedicated variable frequency motor and an independent fan. Constant speed operation. Not affected by frequency conversion. Another thing is that the characteristic curve meets the requirements of frequency conversion.