Current Divider for Accurate High-Current Measurement
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Solution Overview
Problem
Solid state power controllers (SSPCs) face challenges in accurately sensing both steady-state and overcurrents due to the saturation of Hall effect sensors at high currents, requiring large sensors that increase size and weight, and existing solutions like resistive shunts suffer from high power losses.
Innovation Solution
A system utilizing a current divider with two current sensors, where a primary sensor measures steady-state currents and a secondary sensor with higher impedance measures overcurrents, allowing the controller to determine total current accurately without sensor saturation, thereby reducing the size and weight of the SSPC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single Hall effect sensor is used to measure both steady-state and overcurrents, then measurement coverage is comprehensive, but the sensor size and weight increase due to saturation requirements
Solution Approach 1:
The current measurement function is segmented into two separate sensors: a first Hall effect sensor for steady-state currents and a second current sensor for overcurrents. This segmentation allows each sensor to be optimized for its specific measurement range, preventing the first sensor from needing to handle saturation at high currents, thus reducing its size and weight while maintaining measurement accuracy across the full current range.
2Measurement precision
If a single Hall effect sensor is used to measure both steady-state and overcurrents, then measurement coverage is comprehensive, but the sensor size increases to avoid saturation
Solution Approach 1:
The measurement function is divided between two sensors with different impedance values. The first sensor with lower impedance handles steady-state currents, while the second sensor with higher impedance handles overcurrents. This segmentation enables each sensor to maintain accurate measurements within its optimal range without requiring excessive size to prevent saturation, thereby reducing the overall sensor area.
3Measurement precision
If resistive shunts are used for current sensing, then current measurement is achieved, but power losses become quite high
Solution Approach 1:
The patent replaces resistive shunts (which rely on ohmic heating effects) with Hall effect sensors that utilize magnetic field detection. This substitution eliminates the high power losses inherent in resistive shunts while maintaining accurate current measurement capability, as Hall effect sensors draw minimal power and do not dissipate significant energy as heat.
4Measurement precision
If Hall effect sensors are used for current sensing, then non-contact measurement is achieved, but sensor size must be large to handle overcurrents
Solution Approach 1:
The current sensing function is segmented into two specialized sensors: a first Hall effect sensor optimized for steady-state currents and a second current sensor optimized for overcurrents. The second sensor has higher impedance that limits the current through it during overcurrent events, allowing it to remain small and lightweight while still providing accurate measurement of high current conditions.
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 measurement of both steady-state and overcurrents with reduced sensor size and weight, improving the efficiency and compactness of SSPCs while maintaining high accuracy.
Implementation Method 1
The current divider includes a first conductor and a second conductor. The second conductor has a greater impedance than the first conductor.
Implementation Method 2
Hall effect sensors are non-contact sensors that sense current based upon a magnetic field created by current flowing in a conductor. The Hall effect device produces a voltage that is proportional to the current in the conductor.
Data Source
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Figure 2
AI summary
A power controller controls power to a load 12 and includes a primary conductor 28, a current divider 14, first and second current sensors 16, 18, and a controller 26. The primary conductor carries a primary current to the load. The current divider is connected between the primary conductor and the load and includes a first conductor and a second conductor. The second conductor has a greater impedance than the first conductor. The first current sensor provides a first output representative of the primary current, and the second current sensor provides a second output representative of a secondary current in the second conductor of the current divider. The controller determines the primary current to the load based upon the first output when the primary current is less than a threshold value, and based when the second output when the primary current is greater when the threshold value.