Three-Phase Rectifier Using Series-Coupled Switches
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Solution Overview
Problem
Conventional high-voltage rectifiers for three-phase applications face limitations due to the high voltage rating requirements of semiconductor switches, which are not always available for high power ratings, especially in high voltage applications.
Innovation Solution
The use of series-coupled switches in a rectifier circuit allows the DC output voltage to be apportioned among multiple load capacitors, reducing the required power rating of the switches and enabling the use of lower-rated semiconductor switches, such as 6500 Volts IGBTs, to achieve the same output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional single-stage switches are used for high voltage rectification, then the required output voltage can be achieved, but the voltage rating of the semiconductor switches must be extremely high which limits availability
Solution Approach 1:
The patent divides the high voltage rectification function into multiple stages by using series-coupled semiconductor switches. Instead of requiring a single switch to block the entire DC output voltage, multiple switches are connected in series, with each switch blocking only a portion of the total voltage. This segmentation allows the use of lower-voltage-rated switches that are more readily available in the market.
2Adaptability or versatility
If series-coupled switches are used to reduce individual switch voltage ratings, then lower-rated switches become available, but the circuit complexity increases
Solution Approach 1:
The circuit is segmented into multiple voltage blocks using series-coupled switches and corresponding load capacitors. Each switch-capacitor pair forms an independent voltage block that can be controlled separately, simplifying the overall control strategy while enabling the use of lower-voltage switches.
Solution Approach 2:
The load capacitors are pre-charged to specific voltage levels through the series-coupled switches during the rectification process. This preliminary charging action establishes the voltage distribution across the series-connected switches, ensuring that each switch operates within its voltage rating while contributing to the total DC output voltage.
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
This configuration allows for efficient power factor correction without the need for high-voltage semiconductor switches, enabling the production of a 24,000 Volt DC output using switches rated for only 6,000 Volts, thus overcoming the voltage rating limitations of conventional rectifiers.
Implementation Method 1
series-coupled switches coupled to each of the input terminals to apportion voltage on the DC output terminals over the series of terminal sets for respective load capacitors
Implementation Method 2
rectifiers can be used to receive AC (alternating current) input signals and provide DC (direct current) output signals
Data Source
AI summary
Methods and apparatus to provide a rectifier having a high power factor not limited by voltage ratings of switching devices. Methods and apparatus can include pairs of series-coupled switches coupled to a respective phase signal to, along with respective diode pairs, apportion voltage over a series of load capacitors coupled across the rectifier DC output terminals.