Harmonic Control for Three-Phase Motor Heat Reduction
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Solution Overview
Problem
Existing control apparatuses for three-phase rotary machines face challenges in reducing phase current peaks to minimize heat generation and torque ripples, while also managing increased computation loads and noise vibrations, particularly during zero or low-speed rotations.
Innovation Solution
A control apparatus with two power converters and a harmonic component generator that superimposes fifth and seventh harmonic components on the phase current first harmonic component, adjusting their amplitudes to reduce peak current peaks and heat generation, while also considering parameters like rotation speed and element temperature to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a harmonic component with large amplitude is superimposed on the phase current first harmonic component, then the phase current peak is reduced and heat generation is minimized, but torque ripple and noise vibrations increase
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the amplitude and phase of harmonic components based on operating conditions. The control apparatus calculates optimal harmonic parameters that reduce phase current peaks and heat generation while maintaining torque ripple within acceptable limits, resolving the contradiction between thermal management and mechanical smoothness.
2Temperature
If a harmonic component with large amplitude is superimposed on the phase current first harmonic component, then the phase current peak is reduced, but the computation load on the control unit increases
Solution Approach 1:
The patent implements partial action by selectively applying harmonic components only when necessary (e.g., during zero rotation or low-speed rotation when heat generation is critical). The control apparatus evaluates operating conditions and applies harmonic superposition only in regimes where it provides the most benefit, reducing unnecessary computation load while maintaining thermal management effectiveness.
3Area of stationary object
If the installation space is limited, then high radiation performance is required, but heat generation reduction becomes more crucial during zero or low-speed rotation
Solution Approach 1:
The patent converts the harmful effect of limited installation space (which constrains heat dissipation capability) into a benefit by using harmonic component superposition to proactively reduce heat generation at its source. During zero or low-speed rotation when conventional cooling is less effective, the control apparatus applies harmonic currents that reduce phase current peaks, thereby reducing I²R losses and heat generation in the motor windings and power converter.
Data Source
AI summary
A control apparatus (10) for controlling a three-phase rotary machine (80) having two three-phase winding sets (801, 802) includes: two power converters (601, 602) outputting AC currents, having a same amplitude and a phase difference of (30±60×n) [deg], to the two winding sets; a harmonic component generator (20) superimposing a harmonic component on a phase current first harmonic component of a current command value; and two controllers (331, 332) calculating voltage command values for the two power converters according to the current command value. A combination of amplitudes of the phase current fifth and seventh harmonic components to reduce a peak of the phase current first harmonic component is defined as a fundamental amplitude. The harmonic component generator performs a harmonic amplitude reduction process to reduce a phase current peak reduction amount of the phase current first harmonic component from the fundamental amplitude according to a predetermined parameter, and to reduce an absolute value of an amplitude of the harmonic component.