Power conversion apparatus and air-conditioning apparatus
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Solution Overview
Problem
Existing power conversion apparatuses with high-capacitance smoothing capacitors increase in size, and there is a need for a solution to reduce the size while maintaining reliability and cost efficiency, especially for applications like air conditioning systems.
Innovation Solution
A power conversion apparatus with a rectifier circuit, an inverse conversion circuit, and a capacitor that satisfies specific capacitance conditions (C≤350×10^-6PmaxVac² and 100×10^-6PmaxVac²≤C) to reduce fifth and seventh harmonics, using a film capacitor instead of electrolytic capacitors, and optionally omitting a relay between the power supply and the capacitor to minimize size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-capacitance smoothing capacitor is used to smooth direct current voltage, then the voltage smoothing effect is improved, but the power conversion apparatus is increased in size
Solution Approach 1:
The patent changes the capacitance parameter from conventional high values to a specifically optimized range (100×10^-6×Pmax×Vac²≤C≤350×10^-6×Pmax×Vac²). This parameter optimization achieves effective voltage smoothing while significantly reducing the capacitor size and overall apparatus volume, directly resolving the contradiction between smoothing effectiveness and apparatus size.
2Reliability
If a high-capacitance capacitor is used, then the voltage smoothing effect is improved, but the cost of the apparatus is increased
Solution Approach 1:
The patent optimizes the capacitance parameter to a specific range that balances performance and cost. By setting C between 100×10^-6×Pmax×Vac² and 350×10^-6×Pmax×Vac², the invention achieves adequate voltage smoothing without requiring expensive high-capacitance components, thus reducing overall apparatus cost while maintaining manufacturing feasibility.
3Volume of stationary object
If the capacitance is reduced to decrease size, then the apparatus size is reduced, but the voltage smoothing effect deteriorates
Solution Approach 1:
The patent identifies and applies an optimal capacitance parameter range (100×10^-6×Pmax×Vac²≤C≤350×10^-6×Pmax×Vac²) that prevents excessive voltage ripple while keeping the capacitor compact. This optimized parameter range ensures that even with reduced capacitance, the voltage smoothing effect remains sufficient for reliable operation, resolving the contradiction between size reduction and smoothing effectiveness.
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 reduces the size and weight of the power conversion apparatus, enhances reliability, and achieves a desirable cost balance, improving the reliability and reducing the size and cost of air conditioning systems by using a film capacitor and eliminating the need for a relay.
Implementation Method 1
the capacitor is provided between the rectifier circuit and the inverse conversion circuit and has a capacitance C ([F]) that satisfies a condition of a following expression (1)
Data Source
AI summary
A power conversion apparatus includes a rectifier circuit, an inverse conversion circuit, and a capacitor. The rectifier circuit rectifies alternating current power of the alternating current power supply. The inverse conversion circuit inversely converts a voltage Vdc rectified by the rectifier circuit into an alternating current voltage having a certain frequency and applies the alternating current voltage to a motor whose maximum power consumption Pmax is 2 kW or larger. The capacitor is provided between the rectifier circuit and the inverse conversion circuit and has a capacitance C that satisfies a condition of a following expression in relation to an alternating current voltage Vac of the alternating current power supply and the maximum power consumption Pmax.C≤350×10-6PmaxVac2.(1)