Antiparallel Thyristor AC Switch for Equal Current Sharing
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Solution Overview
Problem
In parallel circuits of switching elements, variations in electrical characteristics lead to unequal current sharing, causing increased heat generation due to uneven current distribution, and existing solutions complicate the circuit configuration or increase size and cost.
Innovation Solution
An AC switch with a configuration of four thyristors (two pairs in antiparallel) and a controller that alternates the conduction of thyristors based on detected current values, ensuring equal current sharing and reduced heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a plurality of switching elements are connected in parallel to share current, then heat generation from each switching element is decreased, but variations in electrical characteristics cause unequal current sharing, leading to increased heat generation from some elements
Solution Approach 1:
The patent applies periodic action by alternately switching the first and third thyristors on and off in synchronization with the AC current cycles. This periodic switching ensures that current is distributed alternately between parallel branches, preventing any single thyristor from continuously bearing the full current load and thus reducing heat generation while maintaining equal current sharing through natural electrical characteristic variations during different conduction periods
2Ease of operation
If reactors are connected in series to switching elements to equalize current shares, then current sharing is improved, but the size and cost of the circuit increases
Solution Approach 1:
The patent extracts and eliminates the reactors from the circuit configuration. Instead of using external reactors to equalize current shares, the invention relies on the inherent characteristics of the thyristors and the AC current waveform, combined with synchronized gating signals, to achieve current sharing without adding bulky reactive components to the circuit
3Ease of operation
If a synchronization control circuit is provided to synchronize current application between thyristor switches, then current sharing is improved, but the circuit configuration becomes complicated, increasing size and cost
Solution Approach 1:
The patent merges the synchronization control function directly into the controller that generates gating signals for the thyristors. The controller simultaneously performs current detection, synchronization with AC voltage, and gating signal generation for multiple thyristors, consolidating what would otherwise be separate synchronization circuits into a single integrated control unit, thereby reducing overall circuit complexity
Data Source
AI summary
An AC switch (1) includes a first thyristor (T1), a second thyristor (T2), a third thyristor (T3), and a fourth thyristor (T4). The first thyristor (T1) has an anode connected to an AC power source (2), and a cathode connected to a load (3). The second thyristor (T2) is connected in antiparallel to the first thyristor (T1). The third thyristor (T3) has an anode connected to the AC power source (2), and a cathode connected to the load (3). The fourth thyristor (T4) is connected in antiparallel to the third thyristor (T3). A current detector (5) detects the AC current supplied from the AC power source (2) to the load (3). A controller (6) causes the first thyristor (T1) and the third thyristor (T3) to conduct alternately and causes the second thyristor (T2) and the fourth thyristor (T4) to conduct alternately, for each one-cycle period of the AC current, in accordance with the detection value from the current detector (5).