Full-Wave Amplifier Circuit for Fast Abnormal Current Detection
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Solution Overview
Problem
Existing abnormal current detection circuits for circuit breakers suffer from detection delays due to half-wave amplification, which can lead to damage in high-speed trip scenarios, and are unreliable due to variations in temperature and production process speeds.
Innovation Solution
A full-wave amplifier-based abnormal current detection circuit that generates positive and negative wave-period reference voltage signals with a predetermined difference, using comparators and a combining circuit to output a full-wave combining signal for reliable trip coil driving, with a capacitor for charge voltage comparison and a temperature compensating current source to stabilize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a half-wave amplifier is used to amplify the input signal from the current transformer, then the circuit structure is simpler, but the abnormal current detection is delayed by up to 10 ms
Solution Approach 1:
The amplifier circuit is segmented into two independent parallel paths: a half-wave amplifier path for positive half-cycles and a full-wave amplifier path for negative half-cycles. This segmentation allows each amplifier to operate independently on its respective wave cycle, eliminating the sequential processing delay inherent in single-path amplifiers while maintaining circuit simplicity.
Solution Approach 2:
The circuit utilizes periodic action by processing positive and negative half-cycles of the AC input signal through different amplifier paths alternately. The half-wave amplifier handles positive half-cycles while the full-wave amplifier handles negative half-cycles, ensuring continuous detection without idle periods and reducing overall detection delay.
2Device complexity
If a half-wave amplifier is used, then the circuit configuration is simpler, but the detection may be delayed by a half wave (180 degrees) depending on signal phase
Solution Approach 1:
The detection system is segmented into two parallel detection paths with different amplifier characteristics. One path uses a half-wave amplifier optimized for positive half-cycles, while the other uses a full-wave amplifier optimized for negative half-cycles. This segmentation ensures that regardless of which half-cycle the abnormal current occurs on, there is always an optimized path ready for immediate detection.
Solution Approach 2:
The circuit changes operational parameters by switching between different amplifier configurations based on the input signal phase. When the input is a positive half-cycle, the half-wave amplifier path is activated; when it's a negative half-cycle, the full-wave amplifier path is activated. This parameter change ensures optimal detection performance for all phase conditions.
3Ease of manufacture
If typical electronic devices are used in the detection circuit, then the implementation is easier, but the detection characteristics vary with temperature and production process speed
Solution Approach 1:
The circuit design creates equipotential conditions by using differential amplifier configurations and matched component pairs that maintain balanced operation across temperature variations. The symmetric structure of having both half-wave and full-wave amplifier paths with corresponding comparators ensures that temperature-induced drift affects both paths equally, maintaining detection consistency.
Solution Approach 2:
The circuit incorporates feedback mechanisms through the comparator stages that continuously monitor the amplified signals and provide feedback to maintain stable operation. The comparators compare the amplified input signals against reference levels and provide feedback control that compensates for variations due to temperature and production process differences, ensuring consistent detection characteristics.
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 solution enables fast and reliable abnormal current detection without delay, maintaining operational reliability across temperature and production process variations, effectively preventing damage to load devices and circuits.
Implementation Method 1
a full-wave amplifier for amplifying an alternating current (AC) input voltage signal
Implementation Method 2
a positive wave-period comparator to compare a positive wave-period amplification voltage signal with a positive wave-period reference voltage signal
Implementation Method 3
a capacitor to accumulate electric charges during a time period in which a pulse signal is outputted from the combining circuit
Implementation Method 4
a temperature compensating current source to stabilize performance
Data Source
AI summary
Disclosed herein is an abnormal current detection circuit for circuit breaker, comprising a full-wave amplifier, a positive wave-period comparator for comparing a positive wave-period amplification voltage signal with a positive wave-period reference voltage signal to output a pulse signal, a negative wave-period comparator for comparing a negative wave-period amplification voltage signal with a negative wave-period reference voltage signal to output a pulse signal, a combining circuit for combining pulse signals outputted from the positive wave-period comparator and the negative wave-period comparator to output a full-wave combining signal, a reference voltage generator for generating a reference voltage signal, and a comparative driving circuit section for comparing the combining signal with the reference voltage signal to output a signal for controlling a circuit breaker to be driven to a circuit breaking position when the combining signal is greater or equal to the reference voltage signal.