Motor Control Device Offset Voltage Switching for Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor control devices require significant memory capacity and time to implement noise reduction measures, as they need to store multiple PWM carrier waves, making it difficult to adjust noise levels and increasing costs, especially when additional frequencies are required.
Innovation Solution
A motor control device that uses an inverter to output three-phase terminal voltages based on modified three-phase voltage command values, where an offset voltage is added equally to each phase and switched among multiple candidate voltages to vary the timing of turning on and off the voltages, reducing the need for storing multiple PWM carrier waves and simplifying noise adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple PWM carrier waves of different frequencies are stored to reduce noise, then noise reduction is achieved, but memory capacity requirements increase and implementation complexity increases
Solution Approach 1:
The patent extracts only the essential frequency variation capability from the complex PWM carrier wave storage system. Instead of storing multiple complete PWM carrier waves, the system generates PWM signals by varying the switching frequency dynamically through a frequency variation unit, thereby achieving noise reduction without the memory burden of storing multiple carrier waves.
Solution Approach 2:
The patent implements dynamic frequency variation of the PWM carrier wave. The frequency variation unit continuously or periodically changes the switching frequency around a base frequency, creating a frequency-modulated PWM signal. This dynamic approach replaces the static storage of multiple fixed-frequency carrier waves, reducing memory requirements while maintaining noise reduction effectiveness.
2Object-affected harmful factors
If multiple PWM carrier waves are implemented in the microcomputer to reduce noise, then noise reduction is achieved, but implementation time increases enormously
Solution Approach 1:
The patent establishes a frequency variation pattern in advance through the frequency variation unit, which is designed to vary the switching frequency according to a predetermined pattern. This preliminary configuration of the frequency variation mechanism eliminates the need for time-consuming implementation of multiple separate PWM carrier wave programs, as the system is pre-configured to generate frequency-varied PWM signals dynamically.
3Object-affected harmful factors
If additional PWM carrier waves are added to reduce noise further, then noise reduction is improved, but device complexity and design time increase
Solution Approach 1:
The frequency variation unit serves multiple functions: it varies the PWM switching frequency to reduce noise, and can be configured with different frequency variation patterns to achieve different noise reduction levels. This single multi-functional unit replaces the need for multiple separate PWM carrier wave programs, simplifying the overall system architecture while maintaining the ability to adjust noise reduction effectiveness.
4Object-affected harmful factors
If hardware filters are added to reduce noise when software measures are difficult, then noise reduction is achieved, but cost increases
Solution Approach 1:
The patent replaces the mechanical/electrical hardware filter approach with a software-based frequency variation mechanism. The frequency variation unit, implemented in the microcomputer's control software, varies the PWM switching frequency to push noise components away from sensitive frequency ranges, achieving noise reduction without requiring additional physical filter components and thereby avoiding increased manufacturing costs.
Data Source
AI summary
To provide a motor control device capable of reducing noise without requiring preparation of a plurality of PWM carrier waves, an offset voltage is added equally to each phase of three-phase voltage command values from an inverter to output modified three-phase voltage command values, which are compared to a PWM carrier wave to output three-phase terminal voltages to a motor, and an offset voltage is switched among n offset candidate voltages (n is a natural number of three or more) having different values at set time intervals for output to vary timings to turn on and timings to turn off the three-phase terminal voltages equally for all phases.