Sequential Three-Phase Power Switching to Reduce EMI
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Solution Overview
Problem
The simultaneous application of three-phase power to loads generates rapid current increases, leading to significant electromagnetic interference (EMI) and thermal dissipation in switching devices, particularly in high precision applications where power is applied and removed rapidly.
Innovation Solution
The three phases of the power source are applied sequentially, rather than concurrently, using a synchronization logic circuit to minimize instantaneous current changes and thereby reduce EMI and thermal dissipation by activating and deactivating phases based on zero and mutual cross detection signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If all three phases are applied to the load simultaneously via switching method, then power delivery is achieved, but rapid current increase generates electromagnetic interference (EMI) and thermal dissipation
Solution Approach 1:
The patent segments the simultaneous switching of three phases into sequential switching events. Instead of switching all three phases at once, the controller switches them one after another with time staggering, thereby dividing the harmful simultaneous current surge into separate, controlled events that generate less EMI and thermal dissipation.
Solution Approach 2:
The patent applies preliminary action by detecting zero-crossing points of the AC waveforms before switching occurs. The controller waits for the appropriate zero-crossing detection signal and then activates the switching device at that precise moment, ensuring that switching happens when current is naturally low, thereby preventing rapid current increase and EMI generation.
2Power
If all three phases are applied to the load simultaneously via switching method, then power delivery is achieved, but significant thermal dissipation occurs in switching devices
Solution Approach 1:
The patent segments the simultaneous switching of three phases into sequential switching events. Instead of switching all three phases at once, the controller switches them one after another with time staggering, thereby dividing the harmful simultaneous current surge into separate, controlled events that generate less EMI and thermal dissipation.
Solution Approach 2:
The patent applies preliminary action by detecting zero-crossing points of the AC waveforms before switching occurs. The controller waits for the appropriate zero-crossing detection signal and then activates the switching device at that precise moment, ensuring that switching happens when current is naturally low, thereby preventing rapid current increase and EMI generation.
3Power
If switching occurs when a phase drives high current, then power delivery is maintained, but heat generation in switching circuits becomes significant
Solution Approach 1:
The patent applies preliminary action by detecting zero-crossing points of the AC waveforms before switching occurs. The controller waits for the appropriate zero-crossing detection signal and then activates the switching device at that precise moment, ensuring that switching happens when current is naturally low, thereby preventing rapid current increase and EMI generation.
Solution Approach 2:
The patent converts the naturally occurring zero-crossing points of the AC waveform (which are normally just timing references) into beneficial switching opportunities. By synchronizing switching events with these zero-crossing points, the system turns a passive waveform characteristic into an active strategy for minimizing losses during switching transitions.
Data Source
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AI summary
A circuit and method of applying a three phase power source (104) to a load (160) such that each phase is applied to the load in a manner, such as a predetermined sequence, so as to reduce the electromagnetic interference (EMI) and heat generated during the application of each phase to the load.