Dual Power Switching for Fast Transfer Without Transformer Inrush
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Solution Overview
Problem
Conventional power switching methods in static transfer switches (STS) result in prolonged waiting times and low output voltage due to the need to wait for current to drop to zero before switching, leading to potential equipment shutdowns and high inrush currents.
Innovation Solution
A dual power switching system utilizing a first and second static transfer switch with thyristors and a controller to independently control thyristors based on magnetic flux thresholds, allowing for rapid switching without excessive inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional power switching method waits for current to drop to zero before switching, then high inrush currents are avoided, but switching time becomes too long and output voltage drops too low
Solution Approach 1:
The controller pre-charges the backup power source capacitor before switching occurs, so that when the switch transitions, the backup source is already ready to immediately supply power without waiting for current to naturally drop to zero. This preliminary preparation eliminates the waiting time while preventing inrush currents through controlled charging.
Solution Approach 2:
The patent replaces the conventional mechanical/wait-based switching mechanism with an electronic control system that uses a controller to actively manage the switching process. The controller monitors current levels and actively controls the switching timing and capacitor charging, substituting passive waiting with active electronic management to achieve both fast switching and inrush current prevention.
2Object-affected harmful factors
If the switching waits for appropriate time after current drops to zero, then inrush currents are reduced, but output voltage becomes too low and equipment may shut down
Solution Approach 1:
The backup power source capacitor is pre-charged before the switching event, ensuring that when the switch transitions, power is immediately available at full voltage level. This eliminates the voltage drop that would otherwise occur during the waiting period, preventing equipment shutdown while still controlling inrush currents through the controlled charging process.
Solution Approach 2:
The capacitor in the backup power source acts as an intermediary energy storage element. It accumulates energy before switching and releases it immediately after switching, mediating between the power source and the load to ensure continuous power supply without voltage drops, while the controller manages the charging to prevent inrush currents.
3Productivity
If rapid switching is implemented without waiting for current to drop to zero, then switching time is reduced, but high inrush currents occur in the transformer
Solution Approach 1:
The controller pre-charges the backup power source capacitor to the appropriate voltage level before the switching event. This preliminary charging allows the switch to transition rapidly without waiting for current to naturally decay, while the pre-charged capacitor immediately supplies power, preventing transformer inrush currents through controlled energy transfer.
Solution Approach 2:
The patent changes the timing parameters of the switching operation by using a controller to actively determine the optimal switching moment based on current characteristics, rather than waiting for fixed time intervals. The controller also controls the charging parameters of the backup capacitor, adjusting voltage and current parameters to enable rapid switching without generating harmful inrush currents.
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 system reduces switching time and inrush currents by controlling thyristors to manage magnetic flux within safe limits, ensuring stable power supply to critical loads.
Implementation Method 1
The first static transfer switch includes a first thyristor and a second thyristor connected in reverse parallel. The second static transfer switch includes a third thyristor and a fourth thyristor.
Implementation Method 2
The controller calculates a total magnetic flux according to a current magnetic flux of the inductive device and an expected magnetic flux of the second power source
Implementation Method 3
Since the transformer is an inductive device, when the accumulated magnetic flux is too high, there will be a problem of magnetic flux saturation.
Data Source
AI summary
A dual power switching system selects a first power source or a second power source to supply power to a load coupled to an inductive device. The dual power switching system includes a first thyristor, a second thyristor, a third thyristor, a fourth thyristor, and a controller. The controller calculates a total magnetic flux according to a current magnetic flux of the inductive device and an expected magnetic flux of the second power source. When the power-supplying source is switched, the controller turns off the first thyristor and the second thyristor, and determines whether a commutable time is reached according to a power parameter of the first static transfer switch and the second static transfer switch. When the commutable time is reached, the controller correspondingly turns on at least one of the third thyristor and the fourth thyristor according to the total magnetic flux being less than a threshold.