Motor Drive Device Reducing Startup Noise via Variable Duty Cycle
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Solution Overview
Problem
Synchronous motors experience undesirable noise during startup due to sudden changes in phase current as each phase current rises to a threshold and then drops to zero, which is not effectively managed by existing technologies.
Innovation Solution
A motor drive device with a control circuit that generates a pulse width modulation signal with variable duty cycles to gradually increase and decrease the phase current of a three-phase inverter, preventing sudden drops and thus reducing noise during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase current is allowed to rise and drop suddenly to enable quick motor startup and position detection, then startup speed and detection efficiency are improved, but noise is generated due to sudden current changes
Solution Approach 1:
The patent applies dynamics by making the inverter output duty cycle variable rather than fixed. During motor startup, the duty cycle dynamically changes: initially set to a first value for rapid current rise and position detection, then switched to a second value to gradually reduce current and eliminate noise. This dynamic adjustment resolves the contradiction between fast startup and noise reduction.
Solution Approach 2:
The patent uses preliminary action by first enabling rapid current rise with an initial duty cycle value to complete motor position detection quickly, then proactively switching to a reduced duty cycle value before noise becomes problematic. This two-stage approach预先 establishes the conditions for both fast detection and subsequent noise-free operation.
2Loss of time
If phase current drops suddenly to zero after reaching threshold, then the motor control process is simplified and response time is reduced, but undesirable noise is introduced
Solution Approach 1:
The patent applies dynamics by implementing a dynamic duty cycle adjustment strategy. The inverter output duty cycle transitions from a first value during current rise to a second value during current reduction. This dynamic control enables the system to maintain fast response during position detection while subsequently reducing current gradually to eliminate noise, thus resolving the time-noise contradiction.
3Productivity
If different inductance values are used for different excitation phases, then motor performance is optimized, but phase currents rise at different slopes causing complex control requirements
Solution Approach 1:
The patent applies universality by implementing a unified dual-stage duty cycle control strategy that works across all three excitation phases regardless of their different inductance values. The same control logic (first duty cycle value for current rise, second for current reduction) is universally applied to all phases, simplifying the control system while accommodating phase-specific inductance differences through the flexible duty cycle adjustment.
Data Source
AI summary
A motor drive device can include: a control circuit configured to adjust each phase current of a three-phase inverter of a motor; where the phase current of the three-phase inverter rises from zero to a first threshold during a first time interval; and where the phase current is controlled to drop gradually from the first threshold to zero during a second time interval in order to increase the second time interval.