Three-Phase AC Control Apparatus Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Three-phase AC control systems using pulse width modulation (PWM) generate noise due to equal duty values in two phases, which can cause malfunctions in equipment like aircraft, as the noise superimposes and increases in magnitude, existing technologies cannot effectively reduce this noise.
Innovation Solution
A three-phase AC control apparatus with an equal duty sensing circuit and a PWM signal control circuit that shifts the timing of start and stop of one phase when equal duty values are detected, preventing noise superimposition by adjusting the PWM signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PWM is used to control three-phase AC current, then the output current can be controlled by changing duty value, but noise is generated when two phases have equal duty values causing noise superimposition
Solution Approach 1:
The equal duty sensing circuit detects whether two phases have equal duty values before the PWM switching occurs. When equal duty values are detected, the system preliminarily adjusts the timing of one phase's start and stop signals to prevent noise superimposition before it happens
Solution Approach 2:
The invention introduces an intermediary control signal between the PWM generation and the switching execution. This intermediary signal detects equal duty conditions and mediates by shifting timing, preventing the harmful noise superimposition while maintaining normal PWM control functionality
2Stability of the object's composition
If existing technology changes current control gain to inhibit periodic change from frequency change, then periodic change can be inhibited, but the noise itself caused by switching cannot be reduced
Solution Approach 1:
Instead of reacting to periodic changes after they occur, the invention preliminarily detects equal duty conditions and shifts timing before the switching noise is generated, directly preventing the noise source rather than just inhibiting its periodic manifestation
Solution Approach 2:
The invention changes the timing parameter of the PWM signal when equal duty values are detected. By shifting the start and stop timing of one phase, the duty cycle timing is adjusted to avoid simultaneous switching edges, thereby reducing noise at its source
Data Source
AI summary
A three-phase AC control apparatus includes: an equal duty sensing circuit; and a PWM signal control circuit. The equal duty sensing circuit senses whether any two of a U-phase, a V-phase, and a W-phase of a three-phase AC current have an equal duty value. The PWM signal control circuit outputs, when it is sensed that any two of the U-phase, the V-phase, and the W-phase of the three-phase AC current have the equal duty value, a control signal that shifts a timing of start and a timing of stop of one of the two phases having the equal duty value.