Phase Current Plausibility Check Using Two-Sensor Signal Shifting
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Solution Overview
Problem
Current monitoring systems for electric machines, particularly AC motors, face challenges in determining the plausibility of current measurements, often requiring three separate current sensors, which increases complexity and cost, and fail to effectively diagnose faults in two-sensor systems.
Innovation Solution
A method and system that utilize two current sensors to measure phase currents, employing an all-pass filter with a tuning parameter based on motor velocity to shift and compare signals, determining plausibility by calculating amplitude differences, thereby reducing the need for three sensors and simplifying diagnostic evaluations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three separate current sensors are used to determine plausibility of current measurements, then measurement reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a virtual copy of the third current sensor measurement by mathematically deriving it from the first two sensor measurements using the relationship I3 = -(I1 + I2) based on Kirchhoff's current law. This virtual third measurement allows plausibility checking without requiring a physical third sensor, thus maintaining measurement reliability while reducing device complexity and cost.
2Measurement precision
If signal processing with velocity-dependent tuning parameters is applied, then measurement precision is improved, but computational complexity increases
Solution Approach 1:
The patent implements dynamic signal processing where the tuning parameter of the all-pass filter is adjusted based on the instantaneous velocity of the electric machine. This velocity-dependent tuning allows the filter to adapt to changing operating conditions, improving measurement precision across different speed ranges while keeping the computational complexity manageable through efficient parameter updates.
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 approach allows for effective plausibility determination of current measurements using only two sensors, reducing complexity and cost while identifying potential faults, and can be implemented in systems with two or three phase power supplies, enhancing diagnostic capabilities.
Implementation Method 1
shifting the first current signal by a signal processing component to generate a shifted first current signal having a shifted phase
Data Source
AI summary
A method of evaluating current sensor measurements of an electric machine system includes acquiring a first current signal corresponding to a first measurement of a first phase current of a three phase electric current supply to an electric machine, and acquiring a second current signal corresponding to a second measurement of a second phase current of the three phase electric current supply. The method also includes determining a machine velocity, shifting the first current signal by a signal processing component to generate a shifted first current signal having a shifted phase, the signal processing component including a tuning parameter that is a function of the machine velocity, calculating an amplitude difference between the shifted first current signal and the second current signal, and determining a plausibility of the first measurement and the second measurement based on the difference.