When the commutation of phase B to phase C begins(6384 motor), the current equations of the free-wheeling phase and the conducting phase loop are for the torque ripple problem of permanent magnetless DC motors. Researchers at home and abroad have proposed various solutions(6354 outrunner motor), but various The scheme has its own advantages and disadvantages and lacks adaptability to different working situations.
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When the winding current is switched from one phase to another phase(6384 150kv), a commutation delay occurs, thereby forming a torque ripple during the commutation of the motor. Electromagnetic torque ripple and commutation torque ripple are torque ripples that can be suppressed by control means(5065 motor). However, the optimal current method requires accurate measurement of the back EMF, and real-time detection of the back EMF is difficult.
Commutation torque ripple is a unique problem when brushless DC motors work in 120 ° conduction mode(electric longboard motor). Closing the slot with the closed-end fine method means that the slot is not opened, and the material of the slot is the same as the material of the medicine part. Because the magnetic permeability of Hekou is better(5065 150kv), the closed slot can eliminate torque ripple more effectively than the magnetic slot die, and its practical application is limited.
Magnetic slot die method The magnetic slot die method is to apply a layer of magnetic slot mud on the stator slot of the motor(6354 motor), and then form a slot die with certain magnetic permeability after curing. Therefore, analysis and suppression of torque ripple have become the key to improving the performance of permanent magnet brushless DC motor servo systems(skateboard esc), and have become a hot issue in the field of motor research in recent years.
The overlap time needs to be determined in advance(6374 brushless motor). Its working principle is: when commutation, the power switching device that should be turned off immediately is not turned off immediately, but a time interval is extended, and the switching device that should not be turned on is turned on by an angle in advance(electric longboard esc), which can compensate for the period of commutation The current drops and the torque ripple is suppressed.
The overlap commutation method is a commutation torque ripple suppression method developed earlier(6354 180kv). It is more difficult to select the appropriate overlap time. If it is too big, and if it is small, it will cause insufficient compensation. However, this method must ensure a sufficiently high current sampling frequency and switching frequency to be effective(electric skateboard remote control). The amplitude of the wave is equivalent to 19% of the straight groove.
For this reason, on the basis of the conventional overlapping commutation method, a constant-frequency sampling current regulation technique is introduced(6374 motor 190kv). Practice shows that when the inclined groove angle is 10 °, the fundamental torque amplitude of the cogging torque is equivalent to 90% of the straight groove, it will overcompensate(electric skateboard gloves), and the amplitude of the third harmonic is equivalent to 30% of the straight groove.
This technology uses PWM control to suppress commutation torque ripple during the overlap(6374 brushless outrunner motor), so that the overlap time is automatically adjusted by the current adjustment process, thereby avoiding the problem of the difficulty of determining the size of the overlap interval(e skateboard motor). In addition, although this method is effective for suppressing commutation torque ripple at high speed, it is necessary to solve the switch state offline.