Gradient Induction Heating with Synchronized Inverters
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Solution Overview
Problem
Existing methods for gradient induction heating of workpieces, such as aluminum billets, are limited by the use of supply line frequency, which restricts the range of billet sizes that can be efficiently heated due to fixed penetration depth, leading to inefficient heating and potential heat deformation.
Innovation Solution
The use of pulse width modulated power supplies with tuning capacitors and synchronized inverters allows for adjustable current delivery to multiple induction coils, enabling flexible frequency control and efficient gradient heating across varying workpiece sizes by varying the duration, phase, and magnitude of the inverter output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If supply line frequency (50 or 60 Hertz) is used for induction heating, then the current source is simple, but the penetration depth is fixed and limits the range of billet sizes that can be efficiently heated
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed frequency supply line system to a variable frequency inverter system. The inverter allows the operating frequency to be dynamically adjusted based on billet size requirements, enabling the system to adapt to different penetration depth needs while maintaining simple current source characteristics through standardized inverter technology.
Solution Approach 2:
The patent implements parameter changes by modifying the frequency parameter of the power supply from fixed supply line frequency to variable frequency controlled by inverters. This allows optimization of penetration depth for different billet sizes by adjusting frequency, directly resolving the contradiction between simplicity and adaptability.
2Ease of operation
If a single frequency is used for induction heating, then the equipment is simple to operate, but the heating efficiency varies significantly across different billet sizes
Solution Approach 1:
The system uses dynamic frequency adjustment through inverters to optimize heating efficiency for different billet sizes. The controller automatically selects appropriate frequency settings based on the specific heating requirements, maintaining ease of operation while significantly improving productivity across varying workpiece dimensions.
Solution Approach 2:
The patent incorporates feedback mechanisms where the controller receives information about billet size and heating requirements, then adjusts the inverter frequency accordingly. This closed-loop control ensures optimal heating efficiency is achieved automatically without requiring complex manual adjustments, preserving ease of operation while enhancing productivity.
3Volume of moving object
If the induction field penetrates deeply into the billet cross section, then large billets can be heated, but the penetration depth equation shows this requires lower frequency which reduces heating efficiency
Solution Approach 1:
The patent resolves this contradiction by changing the frequency parameter dynamically. For large billets requiring deep penetration, the inverter lowers the frequency to increase penetration depth. For smaller billets where efficiency is paramount, the frequency is increased. This parameter adjustment allows the system to optimize both penetration depth and heating efficiency based on billet size.
Solution Approach 2:
The system dynamically adjusts operating frequency based on real-time billet size requirements. The controller modulates the inverter output frequency to achieve the optimal balance between penetration depth and heating efficiency for each specific heating scenario, enabling effective heating of various billet volumes without sacrificing productivity.
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 enables efficient gradient induction heating of workpieces of different sizes by optimizing the heating profile, preventing overheating and deformation, and allowing for precise control of the heating process.
Implementation Method 1
Current flowing through each solenoidal coil establishes a longitudinal flux field around the coil that penetrates the billet and inductively heats it
Implementation Method 2
the induced heat is allowed to radiate (soak) into the center of the billet
Data Source
AI summary
An apparatus and process are provided for gradient induction heating or melting of a workpiece with a plurality of induction coils, each of the plurality of induction coils is connected to a power supply that may have a tuning capacitor connected across the input of an inverter. The plurality of induction coils are sequentially disposed around the workpiece. The inverter has a pulse width modulated ac power output that may be in synchronous control with the pulse width modulated ac power outputs of the other power supplies via a control line between the controllers of all power supplies.