Toroidal Current Transformer Circuit for AC DC Fault Detection
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Solution Overview
Problem
Existing current monitoring devices for AC electric power systems are expensive and not capable of effectively detecting both AC and DC faults, particularly with the increasing use of variable-frequency drives in electric motors.
Innovation Solution
A single-coil, toroid-type current transformer circuit that includes an oscillator, a termination element, and an open and short CT detection circuit, connected to a processor for signal processing and system operation manipulation, allowing for the detection of both AC and DC currents through signal data conversion, filtering, and recursive RMS algorithm processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional current transformers are used for AC power systems, then AC current detection is reliable, but DC fault detection capability is lost
Solution Approach 1:
The patent changes the operating parameters of the current transformer by introducing an oscillator that generates alternating excitation signals at different frequencies. This allows the transformer to detect both AC and DC components by analyzing the response at different frequencies, thereby expanding detection capability while maintaining reliability through parameter variation
Solution Approach 2:
The patent employs periodic oscillation signals generated by an oscillator to excite the current transformer. By using periodic action at different frequencies, the system can distinguish between AC and DC fault components, achieving versatile detection capability while maintaining reliable fault identification through frequency-domain analysis
2Adaptability or versatility
If AC/DC capable current sensors are implemented, then both AC and DC faults can be detected, but device cost increases
Solution Approach 1:
The patent makes a standard AC current transformer multi-functional by adding an oscillator and signal processing circuitry. The same transformer hardware can detect both AC and DC faults depending on the excitation signal frequency, achieving universality without requiring separate transformers for different fault types, thus controlling manufacturing cost
Solution Approach 2:
The patent combines the AC current transformer with an oscillator and signal processing unit into a single integrated system. This merging allows the same physical transformer to perform both AC and DC detection functions, reducing the need for multiple separate devices and thereby controlling overall manufacturing cost while achieving versatile detection 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
Enables cost-effective detection of AC and DC faults, facilitating reliable overcurrent protection and metering while maintaining system stability and reducing operational costs.
Implementation Method 1
A conductor 1 of a power system is configured as a primary winding of the current transformer CT1 and extends through a toroid magnetic core 2. Current flowing through the primary winding 1 and passing through the magnetic field of the magnetic core 2 induces a secondary current in the secondary winding 3
Implementation Method 2
The oscillating circuit changes state when the magnetic core M becomes saturated by the current in the windings W1 and W2. Upon saturation of the magnetic core M, there is no change in the current flowing through the current carrying winding W1 or W2
Data Source
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AI summary
A single-coil, toroid-type current transformer circuit for detecting both AC and DC current. The current transformer circuit may include a current transformer and an oscillator electrically connected to the current transformer. The current transformer circuit may further include an open and short CT detection circuit electrically connected to the oscillator for facilitating determination of the connection and stability state of the current transformer. A processor may be electrically connected to an output of the open and short CT detection circuit for performing a series of operations on signal data generated by the open and short CT detection circuit and manipulating the operation of an electrical power system accordingly.