Why do variable frequency motors need to control their axial length?

With the rapid development of power electronics technology and new semiconductor devices, AC speed regulation technology has been continuously improved and enhanced. The gradually improved frequency converter has been widely used in AC motors due to its good output waveform and excellent cost-effectiveness. AC variable frequency speed regulating motors have been successively used for large marine motors, small and medium-sized rolling mill motors, traction motors for railways and urban rail transit, elevator motors, lifting motors for container lifting equipment, motors for water pumps and fans, compressors, and motors for household appliances in steel mills, with good results.

The axial and radial dimensions of marine motors basically determine their overall appearance. For slender, short, and bulky motors, there may be certain technical difficulties in the manufacturing process, and relative errors may have a significant impact on the performance of marine motors. For variable frequency motors, resonance factors that affect the operational performance of marine motors also need to be considered.

Compared with power frequency motors, variable frequency motors require higher rotor balance quality and higher machining accuracy for mechanical parts. Special high-precision bearings should be used to ensure that the vibration performance meets the requirements during high-speed operation. Therefore, the axial length of the variable frequency motor should be controlled to prevent adverse factors such as high-speed vibration caused by excessively long axial dimensions.

Customers who have used variable frequency motors may know that, especially when the frequency range is wide, severe vibrations often occur in a certain frequency band. This is what we call resonance, also known as "resonance", which is the phenomenon where the amplitude of an oscillating system increases sharply under the action of periodic external forces when the frequency of the external force is the same or very close to the natural oscillation frequency of the system. The frequency at which resonance occurs is called the "resonance frequency".

Considering the characteristics of resonance and wide range speed regulation of variable frequency motors, the magnetic field design of variable frequency motors should be further optimized to suppress high-order harmonic magnetic fields and meet the requirements of wideband, energy-saving, and low-noise indicators. Especially for the selection of frequency converters, it is necessary to combine the characteristics of actual working conditions and provide suitable high-quality frequency converters.