Composite Current Sensor Using Hall Effect and Transformer for Wide Bandwidth
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Solution Overview
Problem
Existing current sensing technologies face challenges in achieving wide bandwidth measurements, particularly in high power applications where resistive sensing dissipates power and Hall effect sensors have inadequate bandwidth, leading to poor control system performance and potential damage under fault conditions.
Innovation Solution
A composite current sensing device comprising a Hall effect sensor and a current transformer with a low permeability core, connected in series and an equalizer to flatten their responses, ensuring the low frequency roll-off of the current transformer is lower than the high frequency roll-off of the Hall effect sensor, providing a wide bandwidth measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Hall effect sensors are used for current sensing, then DC and low frequency current measurement is achieved, but bandwidth is inadequate for high frequency applications
Solution Approach 1:
The current sensing function is divided into two separate sensors: a Hall effect sensor for DC and low frequency components, and a current transformer for high frequency AC components. Each sensor operates optimally in its designated frequency range, and their outputs are combined to achieve wide bandwidth coverage from DC to high frequencies.
Solution Approach 2:
The outputs of the Hall effect sensor and current transformer are merged through an equalizer circuit that flattens the combined response across the frequency spectrum. This combination allows the system to achieve both the DC measurement capability of the Hall sensor and the high frequency response of the current transformer.
2Measurement precision
If resistive sensing is used for high power applications, then current measurement is achieved, but power dissipation occurs
Solution Approach 1:
The resistive sensing method is replaced with magnetic field-based sensing using Hall effect sensors and current transformers. These sensors measure current through magnetic field interaction rather than direct electrical contact, eliminating the power dissipation associated with resistive elements while maintaining measurement accuracy.
3Device complexity
If a single sensor is used for wide bandwidth measurement, then device complexity is reduced, but measurement precision across all frequencies deteriorates
Solution Approach 1:
Different parts of the sensing system are optimized for different frequency ranges: the Hall effect sensor is optimized for DC and low frequency measurements, while the current transformer is optimized for high frequency AC measurements. The equalizer circuit then combines these locally optimized measurements to achieve overall wide bandwidth 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
This configuration enhances control system bandwidth and fault protection, enabling faster and more reliable operation of SiC switches by detecting faults in time and utilizing the full operating characteristics of SiC switches, with a sensing range from DC to 5 MHz.
Implementation Method 1
a Hall effect sensor disposed with the line extending axially therethrough wherein a first response is generated by electrical current in the line
Implementation Method 2
a current transformer disposed with the line extending axially therethrough and connected in series to the Hall effect sensor, and having a low permeability core, wherein a second response is generated by the electrical current in the line
Data Source
AI summary
A device for measuring electrical current in a line may include, among other things, a Hall effect sensor wherein a first response is generated by electrical current in the line; a current transformer disposed with the line extending axially therethrough and connected in series to the Hall effect sensor wherein a second response is generated by the electrical current in the line. An equalizer may be connected to the Hall effect sensor and to the current transformer and may be configured to flatten the first and second responses relative to each other. The permeability magnetic path length and cross section of the current transformer is selected such that low frequency roll-off of the current transformer is at a lower frequency than high frequency roll-off of the Hall effect sensor.