Power Converter Relay Switching at Zero Crossing to Inhibit Inrush
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Solution Overview
Problem
Existing power conversion devices face issues with inrush currents during phase switching of AC power supplies due to deviations from zero-crossing points, caused by variations in circuits, components, or environmental changes.
Innovation Solution
A power conversion device with a control circuit that turns on a predetermined power semiconductor device to detect a zero-crossing point in a single-phase AC power supply, then switches the connection destination of power semiconductor devices using a relay circuit within a zero period following this point to inhibit inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If relay circuit switching is performed at zero-crossing point, then inrush current is inhibited, but switching timing accuracy deteriorates due to circuit variations and environmental changes
Solution Approach 1:
The patent applies preliminary action by turning on a predetermined power semiconductor device before detecting the zero-crossing point, and then performing relay circuit switching within a predetermined period after detection. This advance preparation and timed sequence ensures the relay switches at the optimal moment while accounting for circuit variations and environmental changes, thereby inhibiting inrush current effectively.
2Object-affected harmful factors
If additional components are added to improve switching timing accuracy, then inrush current inhibition is improved, but device complexity and cost increase
Solution Approach 1:
The patent employs multi-functionality by utilizing existing power semiconductor devices and control circuits to perform multiple tasks: detecting zero-crossing points, generating control signals, and coordinating relay switching. This approach achieves accurate inrush current inhibition without adding dedicated components, thereby maintaining device simplicity and cost-effectiveness.
Solution Approach 2:
The control circuit performs self-service by using its existing capabilities to detect zero-crossing points and generate appropriate control signals for relay switching. The system leverages its own internal resources rather than requiring external or additional components, achieving accurate timing control while maintaining simplicity.
Data Source
AI summary
In a power conversion device, multiple power semiconductor devices include a first pair of power semiconductor devices and a second pair of power semiconductor devices. The first pair corresponds to a specific phase of a multi-phase AC power supply. The second pair corresponds to another phase. A relay circuit switches a connection destination of the second pair between the specific phase and the other phase. When a single-phase AC power supply is connected to the power conversion device, a control circuit turns on a predetermined one or more of the multiple power semiconductor devices, and detects a zero-crossing point of a power supply voltage of the single-phase AC power supply based on a voltage between contact points of the relay circuit. The control circuit switches a connection destination of the second pair to the specific phase by operating the relay circuit within a zero period following the zero-crossing point.