Abstract
In this paper, the method of harmonic suppression and torque ripple reduction is studied for the structure characteristics and design requirements of a high-speed permanent magnet spindle motor. According to the magnetic circuit analysis and calculation theory of the permanent magnet synchronous motor (PMSM), magnetic reluctance slots are arranged at the two ends of the rotor yoke to change the external magnetic field distribution of the permanent magnet in order to optimize the air gap magnetic density waveform. To obtain air gap flux density waveforms that are close to a sinusoidal distribution and not destroy the permanent magnet under the pre-pressure, several reluctance slots with different widths and depths arranged at two ends of the rotor yoke are used to achieve the sinusoidal distribution. Based on the selection of the pole-slot proportion, skewed-slot and a decrease in the end effect, the effects of the harmonic suppression of the harmonic electromotive force (EMF) and the reduction in the torque ripple are discussed. It is concluded that the additional loss and torque ripple of the high-speed permanent magnet spindle motor can be reduced through a reasonable design.
Highlights
A spindle drive system is a key component of a numerical control (NC) machine
This paper presents a design method for symmetrically setting a series of reluctance slots on the rotor yoke corresponding to both ends of the permanent magnet that can effectively suppress the main pole magnetic field and potential harmonics of the motor, greatly reducing the additional loss and pulsating torque, and at the same time, greatly reduce the difficulty of manufacturing and technological application
For a 4-pole high-speed permanent magnet spindle motor (30000 r/min), from the perspective of the harmonic suppression of the main pole magnetic field and tooth harmonic electromotive force (EMF), a design scheme with a low harmonic loss and low torque ripple is obtained by a comparison of multiple schemes
Summary
A spindle drive system is a key component of a numerical control (NC) machine. The electric spindle has become the commonly used NC machine spindle driving system due to its superior structure and performance. Using a multi-section combined pole structure, different permanent magnet materials, and different structural parameters or arrangement of some permanent magnets in a pole by a pulse width modulation method to weaken the harmonic component of the air gap magnetic field has achieved excellent results [29]–[31] This approach presents higher requirements for the rotor assembly. For a 4-pole high-speed permanent magnet spindle motor (30000 r/min), from the perspective of the harmonic suppression of the main pole magnetic field and tooth harmonic EMF, a design scheme with a low harmonic loss and low torque ripple is obtained by a comparison of multiple schemes. The air friction loss that makes a large contribution to the total loss is proportional to the cube of the motor speed, and the heterogeneity of the rotor outer surface will significantly increase the air friction loss, which is very detrimental to the spindle motor
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