Current Amplifier Protection Circuit for Fast Pulse Faults
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Solution Overview
Problem
Current protection devices for current amplifier circuits are inadequate in protecting against high-speed operations and fail to effectively utilize the safe operation area across a wide range of frequencies from DC to single pulse operations, often resulting in delayed response times and incomplete protection.
Innovation Solution
A protection device that continuously turns down the input voltage to the current amplifier circuit upon detecting an abnormal current value, using a detection circuit and maintenance circuit to output a second abnormality detection signal for a predetermined maintenance time, thereby ensuring protection even during shorter pulse widths than the recovery time of the relay device, and includes bridge circuits and lag lead filter circuits to adjust detection characteristics based on load and frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relay device is used to cut output current, then the current amplifier circuit is protected against abnormal state, but the protection response is delayed due to mechanism operation time and recovery time
Solution Approach 1:
The protection device performs preliminary action by detecting abnormal current and turning down the input voltage to the current amplifier circuit before the relay device completes its mechanical switching action. This preliminary voltage reduction ensures that even during the relay's recovery time, the amplifier receives minimal input signal, preventing damage during high-speed pulse operations shorter than the relay recovery time.
2Reliability
If protection is designed for DC operation, then the element can operate within safe limits at DC, but operation in wide frequency range from DC to single pulse area cannot be protected effectively
Solution Approach 1:
The protection device applies dynamics by making the abnormal current detection threshold dynamic rather than fixed. The detection threshold is adjusted based on the operating frequency and pulse width, allowing the protection circuit to adapt to different operating conditions from DC to single pulse operations. This enables effective protection across a wide frequency range while maintaining safe operation limits.
Data Source
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Figure 3(a)~3(h)
AI summary
In a protection device of a current amplifier circuit, to protect the current amplifier circuit against more high-speed operation than recovery time of a relay device and to protect operation of the current amplifier circuit in a wide range from low frequency side to high frequency side. A protection device (30) includes a detection circuit (32) that detects an abnormal current value of a current amplifier circuit (14) and outputs a first abnormality detection signal. The protection device (30) outputs a second abnormality detection signal continuously for predetermined time that starts from output timing of the first abnormality detection signal, turns down an input voltage value to the current amplifier circuit (14) at receiving timing of the second abnormality detection signal, and outputs a cutting command signal to a relay device (36) at the same timing. The detection circuit (32) includes a load line detection unit (42) that detects abnormality by a current value on a load line and a pulse response characteristic changing unit (44) changes frequency characteristic of abnormality detection operation by the load line detection unit (42).