Variable Frequency Current Sensor Eliminates Aliasing
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Solution Overview
Problem
Conventional current sensors, particularly flux gate sensors, face limitations due to aliasing effects and 'blind' time intervals when measuring currents with frequencies similar to their sampling frequency, leading to disrupted measurements and inability to measure during magnetic saturation.
Innovation Solution
A current sensor arrangement using a ferromagnetic core for magnetic coupling between a primary and secondary conductor, with a controlled voltage source and trigger for periodic magnetic reversal, and a controller to vary the sensor frequency, allowing for continuous measurement and avoiding aliasing by adjusting the voltage amplitude and magnetization range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flux gate sensors are used for current measurement, then measurement precision is improved in a wide dynamic range, but aliasing effects and beats occur when primary current frequency is similar to sampling frequency, disrupting measurement
Solution Approach 1:
The patent applies the dynamics principle by making the sensor frequency variable rather than fixed. The controller dynamically adjusts the sensor frequency based on the detected primary current frequency, ensuring that the sensor operates optimally across different measurement conditions without experiencing aliasing effects or beats that would disrupt measurement reliability.
Solution Approach 2:
The patent implements parameter changes by varying the sensor frequency as a controllable parameter. The controller modifies the sensor frequency parameter in response to changes in primary current frequency, allowing the system to maintain accurate measurement across a wide dynamic range while avoiding the aliasing and beat problems that occur with fixed-frequency sensors.
2Device complexity
If fixed sensor frequency is used, then device complexity is reduced, but time intervals exist where current cannot be measured at all
Solution Approach 1:
The patent applies feedback by using the detected primary current frequency information to control and adjust the sensor frequency. The controller continuously monitors the primary current characteristics and uses this feedback to dynamically set the appropriate sensor frequency, ensuring continuous measurement capability without creating complex fixed-frequency control systems.
Solution Approach 2:
The system transitions from static fixed-frequency operation to dynamic frequency adjustment. The sensor frequency adapts in real-time based on the primary current frequency, eliminating blind time intervals while keeping the control mechanism relatively simple through automated frequency detection and adjustment.
3Measurement precision
If sensor frequency is matched to primary current frequency, then measurement accuracy is improved, but aliasing effects occur that disrupt the measurement
Solution Approach 1:
The patent applies preliminary action by detecting the primary current frequency before taking measurements and pre-adjusting the sensor frequency to an optimal value. This preliminary frequency matching prevents aliasing effects and beats from occurring during the actual measurement process, maintaining both accuracy and measurement integrity.
Solution Approach 2:
The system dynamically adjusts the sensor frequency to optimize measurement accuracy while avoiding harmful aliasing effects. Rather than using a fixed frequency relationship, the sensor frequency adapts continuously based on the primary current characteristics, preventing beats and aliasing while maintaining high measurement precision.
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 and continuous current measurement across a wide range from milliamperes to kiloamperes, reducing aliasing effects and eliminating 'blind' time intervals, thus enhancing the practical application of current sensors.
Implementation Method 1
a ferromagnetic core for magnetic coupling of the primary conductor to a secondary conductor
Implementation Method 2
a trigger connected to the secondary conductor for regular magnetic reversal of the ferromagnetic core, wherein the trigger is designed to make available a bipolar periodic voltage of a certain amplitude so that a resulting periodic secondary current causes the magnetic reversal of the ferromagnetic core
Implementation Method 3
a controller for controlling the voltage source, the controller being designed to vary the sensor frequency during operation of the current sensor arrangement
Data Source
AI summary
A method and an array for measuring a primary current in a primary conductor that is magnetically coupled to a secondary conductor via a ferromagnetic core. In said method, a voltage having a specific amplitude is applied to the secondary conductor such that a secondary current flows for reversing the magnetization of the ferromagnetic core; the secondary current is measured while the magnetization of the ferromagnetic core is reversed in order to obtain a first measured value; the polarity of the voltage is reversed such that a secondary current flows for once again reversing the magnetization of the ferromagnetic core; the secondary current is measured while the magnetization of the core is reversed in order to obtain a second measured value; the primary current is calculated in accordance with the first and the second measured value, the polarity of the voltage being regularly reversed at a certain sensor frequency that is continuously varied.