CT Measuring Circuit Dynamic Switching for Accuracy
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Solution Overview
Problem
The accuracy of current measurement degrades when the measuring circuit is connected to a power supply circuit, as the voltage load influences the current transformation characteristic of the Current Transformer (CT), leading to decreased output current.
Innovation Solution
A measuring apparatus with a circuit switching unit controlled by a switching controller that switches between a state connecting the measuring circuit to the power supply circuit during waiting and a state directly inputting the output into the CT during measurement, effectively isolating the measuring circuit from the power supply circuit during measurement to maintain accurate current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the measuring circuit is connected to the power supply circuit to provide power, then the power supply function is achieved, but the current measurement accuracy degrades due to voltage load affecting CT transformation characteristic
Solution Approach 1:
The patent applies dynamic switching between two circuit states: during measurement, the circuit switches to a state where the measuring circuit is disconnected from the power supply circuit to ensure accurate current measurement; during non-measurement periods, the circuit switches to a state where the measuring circuit connects to the power supply circuit to provide power. This dynamic reconfiguration resolves the contradiction by adapting the circuit topology to the operational requirement.
Solution Approach 2:
The patent implements periodic switching between measurement mode and power supply mode. The switching controller alternates the circuit state between connecting and disconnecting the measuring circuit from the power supply circuit at regular intervals, allowing the system to periodically achieve both accurate measurement and power supply functions without compromising either capability.
2Measurement precision
If the measuring circuit is disconnected from the power supply circuit during measurement, then measurement accuracy is maintained, but the power supply function must be interrupted
Solution Approach 1:
The system alternates between measurement periods and power supply periods in a periodic manner. During measurement periods, the measuring circuit is disconnected to ensure accuracy; during power supply periods, the measuring circuit connects to provide power. This periodic alternation allows both functions to be achieved without continuous compromise of either function.
Solution Approach 2:
The circuit topology dynamically changes based on operational mode. The switching controller adjusts the circuit configuration in real-time, transitioning between a measurement-optimized state and a power-supply-optimized state, thereby maintaining both measurement accuracy and power supply capability through adaptive reconfiguration.
3Measurement precision
If a circuit switching unit is introduced to switch between measurement and power supply states, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The measuring circuit serves dual functions: it acts as both a current measurement device and a power supply source. The same circuit components are utilized for both measurement and power generation, reducing the need for separate dedicated circuits and thereby minimizing the increase in device complexity despite the addition of switching control.
Solution Approach 2:
The measuring circuit itself provides the power supply function without requiring an external power source. The circuit generates its own operating power from the measured current, eliminating the need for separate power supply components and reducing overall system complexity while maintaining measurement accuracy through controlled disconnection during measurement phases.
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 solution allows for accurate current measurement by preventing the voltage load from affecting the current transformation, ensuring high measurement accuracy and reducing measurement errors, even with CTs having poor transfer characteristics, thereby enabling downsizing and cost reduction of the apparatus.
Implementation Method 1
a current transformer (CT) that transforms a current passed through a power line into a current
Implementation Method 2
including a rectifier circuit that rectifies an output current transformed by the current transformer into a direct current
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A measuring apparatus (1) includes a measuring circuit (4) that is an example of a physical amount transformer configured to measure an output current of a CT (2) and a power supply circuit (6) configured to input an output of the measuring circuit. The measuring apparatus also includes a pair of FETs (71,72) configured to switch between a first state and a second state, the first state constituting a circuit inputting the output of the measuring circuit into the power supply circuit, the second state constituting a circuit directly inputting the output of the measuring circuit into the CT, and a switching controller (122) driven by the power supply circuit to control the FETs. The switching controller controls the FETs such that the FETs is in the first state during waiting, and the switching controller controls the FETs such that the FETs is in the second state during measurement.