Motor Current Noise Estimation Using Inverter Bus Current
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Solution Overview
Problem
Existing motor control technologies require additional components for noise determination, increasing the number of components in the motor control device while aiming for high accuracy in current control.
Innovation Solution
A motor control device that includes an inverter, a detection unit, a calculation unit, and a determination unit to detect and extract noise components from motor currents without requiring additional components for offset voltage sampling, using a shunt resistance and A/D converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offset voltage sampling is implemented for noise determination, then measurement precision of bus current is improved, but device complexity increases due to additional components
Solution Approach 1:
The patent merges the offset voltage sampling function with the existing A/D converter that samples the amplified voltage. Instead of using a separate A/D converter for offset voltage sampling, the same A/D converter is utilized for both purposes, thereby reducing device complexity while maintaining measurement precision for noise determination.
Solution Approach 2:
The A/D converter is designed to perform multiple functions: it samples both the amplified voltage from the shunt resistance and the offset voltage. This multi-functional approach eliminates the need for additional dedicated components for offset voltage sampling, resolving the contradiction between measurement precision and device complexity.
2Reliability
If additional components are added for offset voltage sampling, then reliability of noise determination is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent combines the offset voltage sampling capability into the existing A/D converter circuit, eliminating the need for additional separate components. This merging approach maintains the reliability of noise determination while simplifying the manufacturing process by reducing the number of parts that need to be assembled and tested.
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
Enables accurate motor control with reduced components by determining noise magnitude in motor currents, thereby maintaining high accuracy without unnecessary additions.
Implementation Method 1
a voltage generated between both ends of a shunt resistance for detecting a bus current
Implementation Method 2
an amplified voltage obtained by amplifying a voltage generated between both ends of a shunt resistance for detecting a bus current
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
In a motor control device (100), an inverter (10) is configured to convert a direct-current voltage supplied from a direct-current power supply into an alternating-current voltage, and apply the converted alternating-current voltage to a motor (M), a current detector (21) detects a bus current of the inverter (10) by using a shunt resistance (Rs) connected between the direct-current power supply and the inverter, a 3φ current calculator (61) calculates a motor current flowing through the motor (M) based on the bus current, a first extraction unit (91) extracts a noise component included in the motor current from the motor current, and a noise amount determining unit (92) determines a magnitude of a noise in the bus current based on the extracted noise component.