Electronic Overcurrent Release Self-Test Mode
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Solution Overview
Problem
Current test arrangements for electronic overcurrent releases in circuit breakers require significant time and material to verify the functional chain's compliance with tolerance limits, often necessitating complex setups and additional work to disconnect and reconnect components.
Innovation Solution
A software-based test position within the microcontroller activates a test current value and test delay time, allowing the entire functional chain to be tested without external equipment, by setting the test current below the nominal value and delaying the trigger signal to ensure the electromagnetic actuator activates, thus verifying functionality from current detection to actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional test arrangements are used to verify the functional chain compliance, then measurement precision is improved, but device complexity and loss of time increase significantly
Solution Approach 1:
The overcurrent release tests itself using its own components (current transformers, microcontroller, electromagnetic actuator) without requiring external test equipment. The test current is generated internally through the feed connection, and the microcontroller executes the test sequence autonomously, eliminating the need for complex external testing apparatus while maintaining verification accuracy
Solution Approach 2:
The testing function is extracted from the main operational function and implemented as a separate test mode within the microcontroller. By using the second adjustment means to select between operational modes and test position, the testing capability is separated as an independent function that can be activated without affecting normal operation, simplifying the overall system architecture
2Measurement precision
If traditional test arrangements are used to verify the functional chain, then measurement precision is improved, but loss of time increases due to disconnection and reconnection work
Solution Approach 1:
The test arrangement is pre-configured within the microcontroller to automatically sequence the testing operations. The microcontroller is programmed to sequentially activate the electromagnetic actuator, monitor the functional chain response, and evaluate results without requiring manual intervention for each step, significantly reducing testing time while maintaining precision
Solution Approach 2:
The system performs self-testing by utilizing its own operational components during the test mode. The current transformers, microcontroller, and electromagnetic actuator work together in an integrated self-verification process that eliminates the need for external testing equipment and manual disconnection/reconnection procedures
3Ease of operation
If a test position is added to the second adjustment means, then ease of operation is improved, but device complexity increases
Solution Approach 1:
The second adjustment means is designed to serve multiple functions: it can select between different operational modes during normal operation and switch to test position for verification. This multi-functionality allows a single component to handle both operational control and testing initiation, improving ease of operation without requiring separate dedicated test switches or controls
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 method enables efficient testing of the overcurrent tripping function directly at the circuit breaker's location, reducing preparation and wiring needs, ensuring the functional chain's integrity without additional work or equipment, with a test current value around 80% of the minimum nominal current and a delay time of 500 ms for reliable operation.
Implementation Method 1
the primary side of a current transformer, the secondary side of which is connected to a load resistor via a rectifier arrangement. In the unsaturated state of the current transformers, the burden voltages are a proportional image of the phase currents
Implementation Method 2
the secondary side of which is connected to a load resistor via a rectifier arrangement
Implementation Method 3
a trip signal is emitted at the output of the microcontroller, which after amplification is fed to an electromagnetic actuator, which in turn triggers the switching mechanism of the circuit breaker
Data Source
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AI summary
The invention relates to an electronic overcurrent release for circuit breakers, comprising current transformers (11), the primary side of which is in each case linked to one of the phase currents (I1, I2, I3) to be switched and the primary side of which is in each case connected to a load resistor (13) by means of a rectifier assembly (12), to a microcontroller (15) having measurement inputs (41... 43), each of which is operatively connected to one of the load resistors (13), and a signal output (60), which is operatively connected to an electromagnetic actuator (16), a first setting means (S1) for selecting a suitable nominal current value, which is connected to at least one control input (50... 53) of the microcontroller (15), wherein the nominal current value can be selected in a range between a minimum nominal current value and a maximum nominal current value, and a second setting means (S2) for selecting a suitable degree of inertia, which is connected to at least one control input (50... 53) of the microcontroller (15). The invention is characterised in that the second setting means (S2) is additionally provided with a test position and that, when the test position is selected, a fixed test current value below the minimum nominal current value and a fixed test delay time are represented in the microcontroller (15), with a release signal (SA) being present at the release signal output (60) when at least one of the phase currents (I1, I2, I3) exceeds the amount of the value and time of the delay time.