Fluxgate Current Transducer EMI Reduction via Variable Amplitude Control
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Solution Overview
Problem
Fluxgate current transducers face challenges in achieving a high measurement signal to noise ratio while minimizing electromagnetic interference (EMI) when connected to user networks, which affects their electromagnetic compatibility and measurement accuracy.
Innovation Solution
A fluxgate current transducer with a control circuit that generates an alternating voltage with variable time windows of reduced amplitude, allowing the voltage to be zero or less than 50% of the maximum voltage during specific periods after magnetic core saturation, effectively reducing EMI noise and enhancing the measurement signal to noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the amplitude of the alternating voltage applied on the excitation coil is reduced, then electromagnetic interference is reduced, but measurement accuracy deteriorates due to increased noise to signal ratio
Solution Approach 1:
The patent applies periodic action by implementing a control circuit that periodically switches the excitation coil voltage between a first amplitude level (for EMI reduction) and a second amplitude level (for measurement accuracy). The control circuit alternates between these amplitude levels in a periodic manner, allowing the system to benefit from both low EMI and high measurement accuracy at different time intervals.
Solution Approach 2:
The patent applies dynamics by making the voltage amplitude dynamic rather than static. The control circuit adjusts the excitation coil voltage amplitude in real-time based on operational requirements, switching between different amplitude levels. This dynamic adjustment allows the system to optimize both EMI emission and measurement accuracy according to the operational state.
2Object-affected harmful factors
If the voltage is reduced during saturation to reduce EMI, then electromagnetic compatibility is improved, but the signal to noise ratio deteriorates
Solution Approach 1:
The control circuit implements periodic action by alternating the excitation coil voltage between a first amplitude (lower for EMI reduction during saturation) and a second amplitude (higher for improved signal-to-noise ratio). This periodic switching allows the system to maintain EMI compatibility during saturation periods while ensuring adequate signal quality during measurement periods.
Solution Approach 2:
The patent applies parameter changes by dynamically modifying the voltage amplitude parameter based on the operational state. The control circuit changes the voltage parameter from a first amplitude to a second amplitude depending on whether the magnetic core is in saturation or not, thereby optimizing both EMI compatibility and signal-to-noise ratio at different operational stages.
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 significantly reduces EMI noise, improving the measurement signal to noise ratio and ensuring compliance with electromagnetic compatibility standards, while maintaining cost-effectiveness and ease of installation and operation.
Implementation Method 1
The excitation coil is magnetically coupled to a compensation coil or measurement coil 8 having Nm windings. This arrangement has the characteristics of a transformer.
Implementation Method 2
The excitation coil voltage alternatingly saturates the soft magnetic core 4 of the fluxgate device 3, whereby the saturation affects the timing t1′, t2′ of a duty cycle.
Implementation Method 3
the control circuit detects a threshold saturation and reverses the voltage of the voltage generator 9 supplying the excitation coil 6
Data Source
AI summary
Fluxgate current transducer including a fluxgate device comprising a saturable soft magnetic core and an excitation coil, and a processing circuit comprising a control circuit and a voltage generator connected to the control circuit for generating an alternating current in the excitation coil, the voltage generator generating a voltage oscillating between a maximum positive voltage (+Umax) and a maximum negative voltage (−Umax) configured to alternatingly saturate the soft magnetic core. The control circuit is configured to generate a voltage having an absolute value of amplitude less than an absolute value of said maximum positive voltage (+Umax) and said maximum negative voltage (−Umax) voltage during a variable time window (Tn, Tn+1, Tn+2, Tn+3) after detection of the excitation coil current reaching a threshold current (S3) representative of saturation of the magnetic core during at least a subset of a plurality of alternating voltage periods (P).