Motor Control Device Shunt Resistor Current Measurement
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Solution Overview
Problem
Existing motor control systems face challenges in accurately detecting motor currents, particularly when external magnetic fields interfere with hall type current sensors, leading to reduced accuracy and responsiveness, and increased costs.
Innovation Solution
A motor control device and method utilizing two shunt resistors connected to low-side switching elements and a DC-link shunt resistor, with a controller that measures and compares current values to ensure high duty utilization rates and maintain control even if one shunt resistor malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hall type current sensor is used to measure motor current, then the measurement can be performed, but accuracy is reduced when disturbed by external magnetic fields and responsiveness is reduced
Solution Approach 1:
The patent extracts the harmful magnetic sensing function from the current measurement system by replacing hall type sensors with shunt resistance type sensors. This extraction removes the vulnerability to external magnetic fields while maintaining current measurement capability through voltage measurement across the shunt resistor, which is not affected by magnetic interference.
Solution Approach 2:
The patent employs shunt resistance type current sensors which are simpler, more robust, and less susceptible to environmental interference compared to hall type sensors. These sensors provide adequate measurement life for the application while being more resistant to harmful external factors and potentially reducing system cost.
2Measurement precision
If hall type current sensor is used to measure motor current, then the measurement can be performed, but responsiveness is reduced
Solution Approach 1:
The patent replaces the magnetic field-based sensing mechanism of hall type sensors with an electrical voltage measurement approach using shunt resistors. This substitution eliminates the magnetic coupling and inductance effects that limit responsiveness, allowing for faster current measurement and control response.
3Productivity
If multiple shunt resistors are used in the inverter, then duty utilization rate is improved and fault tolerance is enhanced, but device complexity increases
Solution Approach 1:
The patent segments the current measurement function across multiple shunt resistors positioned at different locations in the inverter circuit (input shunt, output shunts per phase). This segmentation enables independent measurement of different current components, improving duty utilization by allowing more flexible switching patterns while providing redundancy for fault tolerance.
Solution Approach 2:
The multiple shunt resistors serve multiple functions simultaneously: they enable current measurement for control, provide redundancy for fault tolerance, and allow for different measurement configurations depending on operational requirements. This multi-functionality justifies the additional components by delivering multiple benefits from a single architectural decision.
4Measurement precision
If shunt resistance type current sensor is used instead of hall type, then accuracy is improved and responsiveness is improved, but cost may increase
Solution Approach 1:
Shunt resistance type sensors are generally simpler and potentially less expensive than hall type sensors, as they eliminate the need for magnetic field sensing components. The patent adopts this approach to reduce implementation cost while maintaining or improving measurement accuracy and responsiveness.
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
This configuration ensures accurate and stable motor control with high duty utilization rates, comparable to in-line shunt resistor types, while allowing continued operation if one shunt resistor fails, by using different conditions for analog-to-digital converters and calculating currents through multiple shunt resistors.
Implementation Method 1
measuring first currents flowing through a first shunt resistor connected to a first low-side switching element included in the inverter and a second shunt resistor connected to a second low-side switching element included in the inverter
Data Source
AI summary
The present disclosure relates to a motor control device and method. The motor control device includes an inverter for driving a motor, a first shunt resistor connected to a first low-side switching element included in the inverter, a second shunt resistor connected to a second low-side switching element included in the inverter, a DC-link shunt resistor in series with the inverter, and a controller for controlling the inverter based on first current value measured through the first and second shunt resistors and a second current value measured through the DC-link shunt resistor.