Inductive Heating Inverter Phase Synchronization

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Solution Overview

Problem

Existing inductive heating devices with multiple coils face challenges in optimizing power factor and reducing switching losses due to varying phase angles between resonant inverters, leading to inefficient heat distribution and temperature variations on heated objects.

Innovation Solution

A control circuit aligns drive frequencies and adjusts phase angles of resonant inverters to operate within an optimal range, ensuring all inverters function optimally by controlling DC voltages and self-inductance or capacitance to maintain a lagging phase mode, thereby minimizing phase differences and reducing switching losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If multiple resonant inverters are operated in parallel with different phase angles to individually optimize each inverter, then each inverter can operate at its optimal power factor, but phase differences cause mutual inductive voltages that weaken magnetic fields at coil boundaries and reduce heat generation density

Engineering Contradiction:

Improvepower factorVSAvoidheat generation density

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The patent synchronizes the phase angles of multiple resonant inverters to operate in unison, merging their magnetic field contributions constructively. This eliminates mutual inductive voltage conflicts and ensures uniform heat generation density across all coil boundaries, while maintaining optimal power factor through coordinated operation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The control system implements a universal phase synchronization mechanism that simultaneously optimizes both the power factor of individual inverters and the overall heat distribution uniformity. By establishing a common reference phase for all inverters, the system achieves dual optimization of energy efficiency and thermal uniformity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Use of energy by moving object

If phase angles of resonant inverters are not synchronized, then each inverter can be independently controlled for optimal power factor, but circulation currents flow between inverters causing overvoltage and potential transistor damage

Engineering Contradiction:

Improvepower factorVSAvoidtransistor safety

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent merges the phase references of all resonant inverters to a common synchronized reference, eliminating phase differences that cause circulation currents. This synchronization prevents overvoltage conditions and protects transistors from damage while maintaining optimal power factor through coordinated inverter operation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The control system implements phase synchronization feedback mechanisms that continuously monitor and adjust inverter phase angles to maintain alignment. This feedback control prevents circulation currents and overvoltage conditions by detecting and correcting phase deviations in real-time, ensuring transistor safety.

Inventive Principle:

Principle #23Feedback

3Productivity

If drive frequencies of resonant inverters are not aligned, then individual frequency optimization is possible, but temperature variations increase on the heated object surface

Engineering Contradiction:

Improveheating efficiencyVSAvoidtemperature uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent aligns the drive frequencies of all resonant inverters to a common synchronized frequency, merging their heating effects uniformly across the workpiece. This frequency synchronization eliminates temperature variations on the heated object surface while maintaining high heating efficiency through coordinated inverter operation.

Inventive Principle:

Principle #5Merging (Combining)

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 approach allows for optimal control of all resonant inverters, ensuring consistent heat distribution and reducing temperature variations on heated objects, while minimizing switching losses and preventing transistor damage.

Implementation Method 1

an inductive heating device using a plurality of inductive heating coils

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

inductive heating power is prevented from sharply decreasing at the vicinity of the boundary of respective inductive heating coils

Methodology Applied

Scientific EffectInductive heating: Induction Heating

Data Source

PatentUS10136476B2Inductive heating device, method for controlling inductive heating device, and program

Publication Date: 2018.11.20 MITSUI E&S CO LTD

AI summary

A control is performed so that phase angles of outputs from resonant inverters fall within a predetermined range under a mutual induction environment. An inductive heating device (100) includes: a plurality of resonant inverters (30a, 30b) that supply power to a plurality of inductive heating coils (La, Lb), respectively, under a mutual induction environment; and a control circuit (40) that aligns drive frequencies so as to be in common among the resonant inverters and controls the drive frequencies commonly so that phase angles of the outputs from the plurality of the resonant inverters fall within a predetermined range. In addition, the control circuit individually controls coil currents flowing through the inductive heating coils so that the phase angles fall within a predetermined range.