| As a product of the combination of vacuum application technology and frequency conversion speed regulation technology,the variable frequency asynchronous motor for vacuum pump has unique advantages.In the process of motor operation,the use of variable frequency power supply will bring a lot of harmonics,which will adversely affect the performance of the motor.At the same time,in order to meet the needs of the site and the wide speed range,the variable frequency asynchronous motor for vacuum pumps usually has two voltage levels,and the windings are connected with ? at low voltage levels.When the winding is connected in ?,the third and multiple harmonic currents in the closed winding will form a harmonic circulation current,which also affects the performance of the motor.Therefore,in order to improve the comprehensive performance of the dual-voltage grade frequency conversion asynchronous motor for vacuum pumps,the problem of harmonic circulation current needs to be solved urgently.In this paper,the model of dual-voltage grade inverter asynchronous motor for vacuum pump is established,and the harmonic and harmonic circulation problems caused by the power supply of the variable frequency power supply are analyzed and suppressed.The change law of the density was studied,the performance parameters of the motor with different harmonic content power supply were obtained through simulation,the change law of the motor performance when the power supply with different frequency power supply was summarized,and the accuracy of the simulation result was verified by combining with the experiment.First,this paper establishes a frequency conversion power supply system model and analyzes the harmonics of the output voltage of the power supply.By adding a filter module to suppress the higher harmonics,waveform acquisition and harmonic analysis are performed on the output voltage of the actual power supply,and the waveform and harmonic analysis results of the two are compared.On the basis of ensuring the availability of the model,a dualvoltage-level variable-frequency asynchronous motor model for vacuum pumps is established and simulated.According to the analysis of the problem of harmonic circulating current in the stator current when ? is connected,the original Y/? is converted into Y/YY connection according to the cause of the formation of the harmonic circulating current,eliminating the closed loop,thereby effectively suppressing the harmonic circulating current and improving Therefore,the problem of motor performance degradation is caused.Then,the causes of harmonics in the motor are analyzed,and the harmonic expressions are deduced and summarized.The negative effects of harmonics on variable frequency asynchronous motors for vacuum pumps are described.The effects of harmonic content and load size of the power supply on the air gap magnetic density of the motor are analyzed through simulation,and the variation rules of each harmonic component are summarized.Finally,the effects of harmonics on variable frequency asynchronous motors for vacuum pumps are analyzed from two aspects,including the effects of harmonics on equivalent circuit parameters and the effects of harmonic content on motor performance,and the harmonic equivalent circuit is summarized.Simulation analysis and experimental verification of the motor's performance change law when the power supply of different frequencies are used.By comparing the simulation results with the experimental results,the correctness of the simulation results is verified. |
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