Converter Input Circuit Layout for Inrush Current Limiting
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Solution Overview
Problem
Conventional sinusoidal PWM converters face challenges in space and wiring savings due to the need for separate components and configurations that include current limiting resistors and electromagnetic contactors, which increase the rated current requirements and hinder compact designs.
Innovation Solution
A power conversion device configuration that integrates a main breaker, main electromagnetic contactor, power supply-side and device body-side reactors, a current detector, smoothing capacitor, and a control unit, along with accessories such as a power-supply phase detection transformer, current limiting resistor, and filter circuit, allowing for shared connections and optimized current limiting operations to minimize initial charging current and reduce component ratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current limiting resistor and electromagnetic contactor are inserted in series into the main power supply line for initial charging, then the initial charging current can be controlled, but the rated current of the electromagnetic contactor must be proportional to the rated capacity of the device body, increasing space requirements
Solution Approach 1:
The patent divides the electromagnetic contactor function into two separate contactors: a main electromagnetic contactor for the main power supply line and an initial charging electromagnetic contactor for the initial charging circuit. This segmentation allows each contactor to be sized appropriately for its specific function, reducing the space required for the main electromagnetic contactor.
Solution Approach 2:
The initial charging function is extracted from the main power supply line by creating a separate initial charging circuit with its own electromagnetic contactor. This extraction allows the main electromagnetic contactor to be sized only for normal operating current, not for initial charging current.
2Ease of manufacture
If separate components are provided for the converter body and accessory parts, then each component can be optimized independently, but wiring complexity and space requirements increase
Solution Approach 1:
The patent merges the initial charging circuit with the main converter body by integrating the initial charging electromagnetic contactor and current limiting resistor directly into the converter body structure. This merging eliminates separate wiring connections and reduces overall wiring complexity while maintaining component optimization.
Solution Approach 2:
The converter body is designed to serve multiple functions: it acts as both the main power conversion unit and the housing for initial charging components. The converter body structure provides both conversion functionality and initial charging functionality, reducing the need for separate accessory components.
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 solution enables space and wiring savings while maintaining reliable operation by minimizing the initial charging current and optimizing the timing of electromagnetic contactor engagement, thus reducing the load on current limiting resistors and improving the practicality of the power conversion device.
Implementation Method 1
a power-supply phase detection transformer that detects a phase and an amplitude of a power supply voltage
Implementation Method 2
a current limiting resistor that suppresses rush current to the smoothing capacitor at an initial turning-on stage of the main power supply
Implementation Method 3
a filter circuit that removes current ripples caused by switching of the switching element
Data Source
AI summary
This power conversion device has: a main breaker and a main electromagnetic contactor connected to a main power supply; a converter body having a switching element; a power supply-side reactor and a device body-side reactor connected to the main electromagnetic contactor; a current detector; a smoothing capacitor; a DC voltage detector that detects a voltage of the smoothing capacitor; a control unit; and accessories. The accessories have: a power-supply phase detection transformer that detects the phase and the amplitude of a power supply voltage; a current limiting resistor that suppresses rush current to the smoothing capacitor at an initial turning-on stage of the main power supply; an electromagnetic contactor which is for turning on current limiting operation and which connects the current limiting resistor and the main power supply; and a filter circuit that removes current ripples caused by switching of the switching element. The main breaker, the main electromagnetic contactor, and an input terminal of the power-supply phase detection transformer in the accessories are connected to one another. The power supply-side reactor, the device body-side reactor, and a filter terminal in the accessories are connected to one another.