STUDY OF ELECTROMAGNETIC TORQUE PULSATIONS IN PRECISION SERVO DRIVES WITH SINUSOIDAL PULSE-WIDTH MODULATION

Abstract

Subject of Research.The paper considers the factors for reducing the pulsations of the electromagnetic torque in a precision instrumental electric drive with sinusoidal pulse-width modulation based on a permanent magnet synchronous motor. It is demonstrated that the estimation of electromagnetic torque pulsations cannot be based only on the spectral characteristics of the phase voltage or current. Method. The method is based on the consideration of sinusoidal pulse-width modulation as a particular case of space-vector modulation. The proposed method provides for estimation of the electromagnetic torque pulsations by the full hodograph of the stator current vector. Main Results. The electric drive simulation results in the environment of MatLab/Simulink are presented. It is shown that a change in the load, modulation algorithm or phase shift of the sweep signal results in a significant change in the pulsations of the electromagnetic motor torque and requires the study of the effect of these factors during optimization of instrumental drive characteristics with an AC motor. The attention is drawn to the phenomenon of low-frequency modulation of electromagnetic torque pulsations brought about by the interaction of interharmonics, that is, harmonics with frequency higher than the frequency of the main harmonic, but not multiple of it. It is shown that the cause of interharmonic in electric drive with pulse-width modulation is the lack of synchronization of the modulation frequency and sweep. Practical Relevance. The results of the work can find application in the design of precision electric drives.

Keywords

• voltage inverter
• torque pulsations
• modulation algorithm
• permanent magnet synchronous motor
• interharmonics
• sinusoidal PWM
• space-vector modulation