Thyristor Short-Circuit Detection Before DC Bus Precharge
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Solution Overview
Problem
Existing short circuit detection methods in direct current circuits, such as those in electric vehicle batteries, fail to effectively prevent damage from inrush currents and short-circuit currents, particularly when using relays or thyristors, due to the time required for relay opening and the occurrence of electric arcs.
Innovation Solution
A short-circuit detection device using thyristors with controlled polarization and operating regimes to detect short circuits by reverse-biasing one thyristor for reverse current charging and precharging a storage capacitor only if necessary, avoiding damage by monitoring voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a relay is used to open the circuit to stop short-circuit current, then the relay can be simply controlled to open, but the relay opening time and electric arcs cause damage to bus components during the opening process
Solution Approach 1:
The invention performs short-circuit detection before closing the relay by using a thyristor to charge the storage capacitor through the bus. If the capacitor charges successfully to the threshold voltage, the bus is confirmed to be free of short circuits, and the relay can be safely closed. This preliminary detection action prevents the need for rapid relay opening later, eliminating the harmful arcs and component damage associated with emergency relay opening.
2Reliability
If the precharge circuit switch is a thyristor, then the thyristor can block short-circuit current, but blocking the thyristor to stop short-circuit current requires additional circuitry
Solution Approach 1:
The invention introduces a detection capacitor as an intermediary element between the thyristor and the control system. The capacitor charges through the bus during a detection phase before relay closure. By monitoring the capacitor voltage, the system can detect short circuits without requiring the thyristor to block current, thus avoiding the need for additional complex blocking circuitry while maintaining reliable short-circuit protection.
3Use of energy by moving object
If the storage capacity is precharged before relay closure, then inrush current is avoided, but if a short circuit occurs during precharging, very large current flows through the switch and can damage other components
Solution Approach 1:
The invention performs a preliminary short-circuit detection phase before the actual precharging operation. During this detection phase, a thyristor temporarily charges the storage capacitor through the bus at limited current. If the capacitor voltage reaches the threshold, the bus is confirmed safe. Only after this preliminary verification does the system proceed to full precharging, ensuring that short-circuit conditions are detected before significant energy is transferred, thus avoiding both inrush current and short-circuit current damage.
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
The device prevents damage to bus components by detecting short circuits before precharging, preserving fuse integrity and ensuring safe connection of the battery to the bus.
Implementation Method 1
the second thyristor is reverse biased and conducts a non-zero reverse current charging the storage capacity
Implementation Method 2
first and second thyristors coupled to the voltage source and to the bus
Implementation Method 3
at least one capacitive element forming a storage capacity
Data Source
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AI summary
The present description relates to a short-circuit detection device (100) in a DC circuit comprising a voltage source (102), a bus having at least two conductive elements (104, 106) each coupled to one of the terminals of the voltage source, first and second thyristors (112, 114) coupled to the voltage source and the bus, and at least one capacitive element forming a storage capacity (118) each of whose electrodes is coupled to one of the two conductive elements of the bus, the short-circuit detection device comprising at least one control circuit (124) configured to control the biases and operating regimes of the first and second thyristors such that a short-circuit detection phase is implemented before a pre-charge of the storage capacity.