Radiation-Hardened Current Sensor With Active Frequency Separation
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Solution Overview
Problem
Conventional current sensors are impractical in radiation-exposed environments due to the difficulty and expense of producing radiation-hardened components, particularly in space applications where components like Hall effect sensors are sensitive to radiation.
Innovation Solution
A radiation-hardened current sensor with an active filter is designed using a DCCT and ACCT, along with a self-oscillating modulator and active filter to accurately sense current from DC to 10 MHz, employing a comparator to control switches and maintain magnetic flux density within limits, and an active filter to isolate DC and low-frequency AC components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current sensors are used in radiation-exposed environments, then current sensing can be performed, but the components become sensitive to radiation and are difficult and expensive to produce as radiation-hardened versions
Solution Approach 1:
The current sensor is divided into two separate transformer components: a DC current transformer (DCCT) for sensing DC and low-frequency AC current, and an AC current transformer (ACCT) for sensing higher frequency AC current. This segmentation allows each component to be optimized for its specific frequency range and radiation environment, avoiding the need for a single complex radiation-hardened sensor that would be difficult and expensive to manufacture
Solution Approach 2:
An active filter is introduced as an intermediary component between the DCCT and ACCT. The active filter isolates DC and low-frequency AC components from the ACCT, allowing the ACCT to focus on higher frequency AC current sensing. This intermediary structure simplifies the requirements for each transformer component, making them easier to manufacture with radiation hardness
2Adaptability or versatility
If a single transformer is used to sense current across a wide frequency range, then frequency versatility is achieved, but the transformer cannot accurately distinguish between DC, low-frequency AC, and high-frequency AC components
Solution Approach 1:
The frequency sensing range is segmented into three distinct bands: DC and low-frequency AC (handled by DCCT), mid-frequency AC (handled by active filter), and high-frequency AC (handled by ACCT). Each component is专门ized for its frequency range, enabling precise measurement and separation of different frequency components across the entire spectrum from DC to 10 MHz
Solution Approach 2:
The system dynamically routes different frequency components through different processing paths based on their characteristics. The self-oscillating modulator dynamically adjusts the DCCT operation, and the active filter dynamically separates frequency components, allowing the system to adaptively handle the full frequency range with precise component separation
3Power
If the magnetic flux density is allowed to exceed hysteresis limits, then the transformer can handle higher current levels, but current spikes and measurement inaccuracies occur
Solution Approach 1:
A self-oscillating modulator with comparator provides feedback control to the DCCT. The comparator monitors the magnetic flux density and controls the DCCT excitation to maintain operation within the linear portion of the hysteresis curve. This feedback mechanism prevents current spikes and measurement inaccuracies while enabling the system to handle higher current levels through controlled oscillation
Solution Approach 2:
The system preemptively prevents magnetic flux density from exceeding hysteresis limits by using the comparator to detect approaching limits and adjust the DCCT excitation accordingly. This preliminary anti-action prevents current spikes and measurement errors before they occur, maintaining accuracy while maximizing current handling capability
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
The sensor effectively senses current across a wide frequency range while withstanding radiation, providing accurate measurements in harsh environments by isolating and correcting current spikes, ensuring reliable operation in space applications.
Implementation Method 1
a DC current transformer (DCCT) used to sense DC and low frequency AC current
Implementation Method 2
an AC current transformer (ACCT) used to sense higher frequency AC current
Implementation Method 3
the comparator closes the first switch that controls a supply of a positive voltage and opens the second switch that controls a supply of a negative voltage until the DCCT exceeds the upper limit of the magnetic hysteresis characteristic
Data Source
Figure 1
AI summary
A radiation hardened current sensor to sense direct current (DC), low frequency alternating current (AC), and high frequency AC includes a DC current transformer (DCCT) (110) including a primary DCCT winding (111= and a secondary DCCT winding (112). A self-oscillating modulator (120) is coupled to the secondary DCCT winding of the DCCT to maintain a magnetic flux density of the DCCT at an upper limit and a lower limit of a magnetic hysteresis characteristic of the DCCT. An active filter (140) passes only the DC and the low frequency AC from the DCCT as an output. An AC current transformer (ACCT) (160) including a primary ACCT winding (161) and a secondary ACCT winding (162). The output of the active filter is coupled to the ACCT and the secondary ACCT winding provides the high frequency AC.