Induction Heating Inverter Phase Control
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Solution Overview
Problem
Conventional induction heating devices with multiple coils face challenges in maintaining minimum phase angle control across zones, leading to reduced power factor and operational issues due to changes in material phase and temperature, causing uneven heating and potential reverse current flows.
Innovation Solution
Control one or more inverters to operate at a minimum phase angle, ensuring the output voltage exceeds mutual induction voltages, and adjust power supply voltage to maintain a phase angle of 30° or greater, using a converter to modulate the power supply voltage and generate equivalent sine-wave voltages to prevent reverse currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiple induction heating coils are disposed close to each other to prevent temperature drop between coils, then temperature uniformity is improved, but mutual induction voltages are generated causing circulation currents and uneven heating at boundaries
Solution Approach 1:
The invention divides the induction heating system into multiple independent zones, each with its own inverter and control system. By segmenting the power supply units and controlling each zone independently with synchronized current phases, the system prevents circulation currents while maintaining temperature uniformity across the heated material surface.
Solution Approach 2:
The invention applies local quality control by enabling independent power control for each induction heating zone. Each zone can be individually adjusted to compensate for boundary effects and mutual induction, ensuring uniform heating across the entire surface while preventing harmful circulation currents in specific locations.
2Object-generated harmful factors
If current synchronization control is applied to prevent circulation currents, then harmful current flows are reduced, but control complexity increases due to phase and amplitude coordination requirements
Solution Approach 1:
The invention implements feedback control mechanisms in each power supply unit to monitor and adjust current phase and amplitude. By using feedback to synchronize currents across multiple inverters and detect/eliminate circulation currents, the system achieves effective control while managing complexity through decentralized intelligent control algorithms.
Solution Approach 2:
The invention employs dynamic control where each inverter continuously adjusts its output based on real-time conditions. The control system dynamically coordinates phase and amplitude across multiple inverters, enabling adaptive prevention of circulation currents while maintaining flexibility to handle varying heating requirements.
3Power
If inverters are operated in parallel to provide sufficient power, then heating capacity is improved, but mutual power transfer occurs causing over-voltages and reduced efficiency
Solution Approach 1:
The invention segments the power supply into independent units, each feeding its own induction heating zone. This segmentation prevents mutual power transfer between inverters by isolating their electrical paths, while still achieving high heating capacity through parallel operation of multiple independent units with synchronized control.
4Use of energy by moving object
If phase angle is minimized to improve power factor, then energy efficiency is improved, but output voltage may fall below mutual induction voltage causing operational issues
Solution Approach 1:
The invention dynamically adjusts operating parameters including phase angle and output voltage based on real-time conditions. By optimizing the phase angle to maintain adequate power factor while ensuring output voltage remains above mutual induction voltage thresholds, the system achieves both energy efficiency and operational reliability through adaptive parameter control.
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 ensures normal operation and maximum power output in zones with minimal phase angle control, reducing the required rating of conversion devices and maintaining high power factor efficiency.
Implementation Method 1
an induction heating coil is divided into multiple coils and a power control is performed by connecting a high-frequency power source (e.g., an inverter) to each of the divided induction heating coils individually
Implementation Method 2
mutual induction inductances M are present, thereby generating mutual induction voltages
Data Source
AI summary
The present invention includes: a plurality of induction heating coils (11, 12, 13) which are disposed adjacently; capacitors (21, 22, 23) each of which is connected in series thereto; a plurality of inverters (30, 35, 31) each of which applies a high frequency voltage converted from a DC voltage to each series resonant circuit of the induction heating coil and the capacitor; and a control circuit (50) which operates the plurality of the inverters with a same frequency and current synchronization, controls so that a phase difference becomes minimal at a specific inverter, which supplies the maximum power to the plurality of the induction heating coils, between the high frequency voltage generated therefrom, and a resonant current flowing the series resonant circuit, and set a DC power supply voltage Vdc applied to the plurality of the inverters so that the output voltages (Vinv) become greater than mutual induction voltages (Vm).