Motor Controller Reducing Torque Ripple via Harmonic Current Adjustment
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Solution Overview
Problem
Consequent pole motors with a salient pole rotor experience magnetic unbalance due to uneven magnetic flux distribution, leading to increased torque ripple and vibration noise when supplied with sinusoidal current, as the salient pole lacks magnetic flux compelling force and induces magnetic flux unevenly.
Innovation Solution
A controller that adjusts fundamental wave current using high-order currents for third and ninth order components in the q-axis to reduce torque ripple by generating excitation currents with predetermined phase differences, utilizing a magnet as one magnetic pole and a salient pole of the core as the other, thereby compensating for the magnetic flux directivity and amount differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fundamental wave current (sinusoidal current) is supplied to the consequent pole motor, then the motor operates in the same manner as a normal motor, but torque ripple and vibration noise increase due to magnetic unbalance
Solution Approach 1:
The patent applies parameter changes by modifying the current waveform parameters - specifically adding third-order and ninth-order harmonic components to the fundamental sinusoidal current. This changes the current characteristics from pure sine wave to a waveform with controlled harmonics, which compensates for the magnetic unbalance caused by the salient pole structure and reduces torque ripple and vibration noise
2Loss of substance
If a salient pole of a core is used as a substitute for a magnetic pole, then the number of magnets is reduced by half, but magnetic flux distribution becomes uneven causing magnetic unbalance
Solution Approach 1:
The patent compensates for the non-uniform magnetic flux distribution caused by using salient poles instead of magnets by adjusting current parameters. Specifically, third-order and ninth-order harmonic current components are added to counterbalance the magnetic unbalance, thereby maintaining stable and uniform magnetic flux distribution across the air gap despite the reduced magnet quantity
Solution Approach 2:
The patent converts the harmful effect of uneven magnetic flux distribution (caused by salient poles) into a beneficial outcome by using harmonic current components. The harmonic currents create compensating magnetic fields that transform the magnetic unbalance into a balanced state, reducing torque ripple and vibration while maintaining the cost-saving salient pole structure
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The controller effectively reduces torque ripple and vibration noise by adding high-order current components, improving the magnetic flux distribution and rotor balance, resulting in smoother motor operation.
Implementation Method 1
the salient pole itself does not have a magnetic flux compelling force (induction). Thus, depending on the present positional relationship between the salient pole and the teeth of the opposing stator, the magnetic flux at the rear side of the magnet may not be evenly diffused
Data Source
AI summary
A controller for use with a motor including a stator, around which three-phase coils are wound, and a rotor, which includes a magnet functioning as a first magnetic pole and a salient pole of a core functioning as a second magnetic pole. The controller supplies the three-phase coils with excitation currents having a predetermined phase difference from one another to drive and rotate the rotor. The controller includes a current adjustment unit that adjusts a fundamental wave current using high-order currents for third order and ninth order components in a q-axis to reduce torque ripple. The excitation current is generated based on the fundamental wave current adjusted by the current adjustment unit.