Isolated Output Module Current Limiting for Fault Ride-Through
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Solution Overview
Problem
Industrial output modules lack electrical isolation between terminals, leading to potential damage from high current spikes, which can cause unintended shut-downs and high-frequency oscillations, compromising safety and availability.
Innovation Solution
The output module incorporates a transformer for electrical isolation between each terminal and a current limiting circuit to prevent voltage drops, ensuring continuous operation during high current draws and monitoring for short circuits, with a control circuit that selectively connects the transformer to the terminal and limits current to a predefined threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple output terminals are connected in parallel to a single power supply, then the power supply can drive multiple devices, but high current at one terminal can affect other terminals through the shared power path
Solution Approach 1:
The patent divides the power distribution system into separate isolated paths for each output terminal. Each terminal has its own transformer and power supply path, preventing current interference between terminals while maintaining the ability to drive multiple devices independently.
Solution Approach 2:
Transformers are introduced as intermediary devices between the power supply and each output terminal. These transformers provide galvanic isolation, allowing power transmission while blocking harmful current spikes and interference from affecting other terminals.
2Reliability
If electrical isolation is provided between output terminals using transformers, then high current spikes are contained, but the device complexity increases
Solution Approach 1:
The patent integrates multiple functions into each terminal's isolated power path: the transformer provides both galvanic isolation and voltage transformation, while the control circuit handles both switching control and current monitoring. This multi-functionality reduces the need for separate dedicated components for each function.
3Reliability
If current limiting is implemented to prevent high current damage, then terminal protection is improved, but voltage drops may occur affecting continuous operation
Solution Approach 1:
The current limiting circuit dynamically adjusts its operation based on real-time current conditions. During normal operation, the circuit allows full current flow without limitation. When high current is detected, the circuit activates limiting measures while maintaining voltage stability through dynamic control, preventing both damage and excessive voltage drops.
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 prevents damage from high current spikes, maintains continuous operation, and reduces high-frequency oscillations, ensuring safe and reliable operation of industrial controllers by isolating each output terminal and limiting current, thus enhancing safety and availability.
Implementation Method 1
An isolation circuit for each output terminal includes a transformer with a primary winding electrically connected to the power source and a secondary winding at which an isolated output voltage is provided
Implementation Method 2
A current limit circuit is provided between the isolated output voltage and the output terminal to limit the current output from the transformer to a predefined threshold
Data Source
Figure 1
Figure 2~3
Figure 4A~4C
AI summary
An output module (10) for an industrial controller provides electrical isolation between each of the output terminals in the module. The output module receives control signals (16) from the industrial controller (14) indicating a desired output state for each of the output terminals and selectively connects power from the output of the electrical isolation to the output terminal. During normal operation, a switching device (60A, 60B) connects the power to the output terminal responsive to the control signal. A current sensor monitors the current conducted at the output terminal. If the current exceeds a predefined threshold, a current limit circuit (40A, 40B) clamps the current being output at the terminal. A control circuit may allow the output terminal to ride through a temporary spike in current or disable the output terminal if a fault condition is detected.