Induction Heating System Phase Balance via Intermediate Apparatus
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Solution Overview
Problem
Induction heating apparatuses using three-phase AC power supplies often result in uneven heat distribution and phase current imbalance, particularly when directly connected, leading to a state where no current flows in one phase, and existing solutions like Scott connection transformers are costly and inefficient.
Innovation Solution
An induction heating system that uses a three-phase AC power supply with an intermediate apparatus featuring an iron core and a coil with an even number of turns, where the induction heating coil is connected to one phase and the midpoint of the intermediate coil, and the intermediate coil is connected to the remaining two phases, ensuring balanced current flow among phases without the need for a Scott connection transformer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-phase AC is taken out from three-phase AC by direct connection to run induction heating apparatus, then the apparatus can operate with simple connection, but phase current balance becomes unbalanced (1:1:0) and one phase has zero current flow
Solution Approach 1:
An intermediate apparatus is introduced between the three-phase power supply and the induction heating coil. This intermediate apparatus includes a coil with even number of turns wound on an iron core, with its start point connected to one phase, end point connected to another phase, and midpoint connected to the induction heating coil. This intermediary structure enables balanced current distribution across all three phases while maintaining simple operation.
2Ease of operation
If Scott connection transformer is used to take out single-phase AC from three-phase AC, then phase current balance is improved, but cost and space requirements increase significantly
Solution Approach 1:
The patent replaces the expensive and complex Scott connection transformer with a simple intermediate apparatus consisting of a coil wound on an iron core. This simplified structure achieves the same phase current balance function at much lower cost and with minimal space requirements, effectively substituting a complex permanent solution with a simple, economical alternative.
3Ease of manufacture
If induction heating coil is directly connected to two phases of three-phase supply, then connection is simple, but heat generation distribution becomes uneven and power factor reduces
Solution Approach 1:
The intermediate apparatus serves as a mediator that transforms the unbalanced two-phase connection into a balanced three-phase connection. By connecting the induction heating coil to the midpoint of the intermediate coil, the system achieves uniform heat generation distribution and improved power factor while maintaining connection simplicity.
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 prevents the occurrence of a phase with zero current flow, maintains balanced three-phase currents, and allows for efficient heating by adjusting magnetic resistance and using power control devices to optimize output, even with a three-phase AC power supply.
Implementation Method 1
an intermediate apparatus that intervenes between the single-phase induction heating apparatus and the three-phase AC power supply and includes an iron core for forming a closed magnetic circuit and a coil wound on the iron core
Implementation Method 2
An induction coil of an induction heating apparatus causes a reduction in power factor or unevenness in heat generation distribution when magnetic fluxes having different phases intersect with each other within the same magnetic circuit
Data Source
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AI summary
The present invention intends to, when running one induction heating apparatus using a three-phase AC power supply without the use of a Scott connection transformer, prevent the occurrence of a phase where no current flows. The present invention is an induction heating system 100 that uses a three-phase AC power supply 4 to run an induction heating apparatus 2 including an induction heating coil 21, and the induction heating system 100 has an intermediate apparatus 3 including a coil 31 that is wound on an iron core 30 forming a closed magnetic circuit and has an even number of turns. In addition, a winding start point 21x of the induction heating coil 21 is connected to the U phase of the three-phase AC power supply 4 and a winding end point 21y of the induction heating coil 21 is connected to a midpoint 31z of the coil 31 of the intermediate apparatus 3. Further, a winding start point 31x and winding end point 31y of the coil 31 of the intermediate apparatus 3 are connected to the V and W phases of the three-phase AC power supply 4, respectively.