| Induction motors are widely used in marine auxiliary equipment.With the emphasis on vibration and noise,the vibration and noise has become an important technical indicator of motors.In the past,the research on motor vibration focused on the motor itself,with the development of frequency control technology,the application of variable frequency induction motor is becoming more extensive than before.However,the induction motro will introduce harmonic under the frequency conversion power supply,which will aggravate the motor vibration.Compared with the traditional straight slot rotor,the skewed slot rotors is used in engineering to improve the performance of the motor.Therefore,it is important to analyze the influence of frequency conversion power supply and skewed slot rotor on the electromagnetic vibration of induction motor.In this paper,a 7.5kW induction motor is taken as the research object.The analytic solution and finite element simulation are used to analyze the electromagnetic excitation characteristics of the induction motor under sinusoidal power supply.Based on the finite element model,the influence of variable frequency power supply and skewed slot rotor on the electromagnetic excitation is explored.In order to explore the electromagnetic excitation characteristic of motor under frequency conversion power supply,the harmonic components in the output voltage of SPWM inverter circuit.It is found that the harmonic frequency in the output voltage is related to the switching frequency of the converter.On this basis,the expression of electromagnetic force under frequency conversion power supply is deduced,and the field-circuit coupled finite element simulation model is built to obtain the frequency of additional electromagnetic force under variable frequency power supply.Aiming at the skewed solt rotor,the principle of weakening the magnetic field tooth harmonics is analyzed,and the multi-section finite element simulation model is used to analyze the weakening effect of the skewed slot rotor on the tooth harmonics of electromagnetic force.The weakening effect of three skewed slot rotors with different skewed distance and the double skewed slot rotor on the electromagnetic excitation is further compared and analyzed.On the excitation separation test bench,the air gap flux density waveform is indirectly measured by the full-pitch coil and tooth-wound coil.By testing the magnetic flux density waveform and vibration response,the optimization effect of three rotors with different skewed distances and double skewed slot rotor is compared,and the correctness of the simulation results is verified. |
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