This is how induction heating works
When an alternating current flows through a coil, it creates a magnetic field. The field’s strength fluctuates based on the current passing through the
coil. It is primarily concentrated within the coil’s enclosed area, with its intensity determined by the current’s strength and the number of turns in
the coil.
When an electrically conductive object, such as a metal bar, is placed inside the coil, eddy currents are induced within it. The resistance of the
material generates heat in the regions where these currents flow. A stronger magnetic field enhances the heating effect, but the overall heat
generation also depends on the object’s magnetic properties and its distance from the coil.
Eddy currents generate their own magnetic field, which opposes the original field produced by the coil.This resistance delays the penetration of the
original field into the object’s core. The eddy currents are strongest near the surface of the heated object and gradually weaken as they move
toward the centre.
The penetration depth is the distance from the surface of the heated object to the point where the current density decreases to 37%. This depth
increases as the frequency decreases. Therefore, selecting the appropriate frequency is crucial to achieving the desired penetration depth.
What are the benefits of induction heating?
Advantages of Induction Heating:
●Faster: Induction heating generates heat instantly, achieving a uniform surface temperature of 1,000°C in under a second for small metal
components.
●More Accurate: The process delivers precise temperatures exactly where needed, ensuring optimal heating for individual workpieces. A wide range
of frequencies allows control over penetration depth, while customized induction coils accommodate various shapes and sizes, maximising efficiency
with minimal energy consumption.
●Highly Controllable: Advanced transistorised converters and process control software enable complete regulation of the heating process. Ramp-up and dwell times can be preset and repeated as needed, with inbuilt telemetry options for remote diagnostics and monitoring.
●Repeatable: Induction heating ensures consistent results by maintaining stable heating cycles. The heat output from a frequency converter typically
varies by only 1-2%, allowing precise duplication of key parameters like temperature, penetration depth, heat pattern, and heating speed.
●Cleaner, Safer, and More Compact: With no gas, open flames, or significant ambient heat increase, induction heating is a safer and more efficient
alternative to traditional methods. Additionally, it requires less floor space than ovens, making it a more sustainable solution.
The technical advantages of induction heating provide
three major benefits:
Improved Throughput
Incorporating induction heating into the production line enhances efficiency by reducing lead times and accelerating throughput. The heating process is quicker compared to open flame or oven methods.With precise repeatability, you can achieve faster results by getting it right the first time.
Better and Consistent Quality
Induction heating enhances quality by allowing precise application of pre-set temperatures to specific areas of each workpiece. Custom designed induction coils ensure predictable heat patterns, while controlled heat delivery prevents damage to surrounding components and materials.
Reduced Costs
Induction heating lowers costs by shortening lead times and increasing throughput. In line integration reduces administrative and logistics expenses
while improving production yields. Fast heat cycles, precise temperature control, and repeatable processes minimize waste and scrap. Energy costs
drop since only the necessary material is heated, avoiding losses typical of conventional ovens. (ENRX frequency converters further enhance savings
with superior efficiency and power factors.) Additionally, eliminating hazardous gas and open flames can lead to lower insurance premiums.
Selecting the Best Induction Heating Solution
Choosing the right induction heating system depends on several factors, including the material, shape, and size of the workpiece, as well as the
required heating depth and temperature.
How Much Energy Do You Need?
Before determining your energy requirements, consider these key factors:
●Material Type: Different materials (steel, copper, brass, etc.) have varying thermal properties and energy demands.
●Workpiece Dimensions: Size and shape impact heating efficiency and power requirements.
●Production Rate: The number of workpieces to be heated per hour affects total energy consumption.
●Final Temperature: The target temperature determines the amount of energy needed for proper heating.
By analysing these factors, you can accurately calculate the optimal energy input for your induction heating process.
Calculate Your Energy Requirements
Step 1: Determine the material’s energy absorption rate.
Refer to standard values for common materials (e.g., steel, copper, brass) to find the energy required per kilogram.
Step 2: Calculate the specific power requirement.
Multiply the material’s energy absorption rate by your desired hourly production (kg/hour).
Step 3: Adjust for equipment efficiency.
Check the efficiency level of your induction heating equipment (typically available in manufacturer specifications).
Divide the specific power requirement by the efficiency rate to get the total power requirement. This ensures you have the right energy input for
optimal heating performance.
Typical Induction Heater Efficiency Levels
The efficiency of an induction heater depends on the material being heated and the coil design used. Standard efficiency levels assume the use of
enveloping multi-turn coils.However, different coil designs can influence overall efficiency.
For example, copper typically has a lower efficiency rate of 0.1–0.2, due to the specific coil types commonly used. To achieve accurate power calculations, it’s important to factor in the efficiency level based on the coil design and material properties.
Selecting the Right Frequency
Choosing the correct frequency is essential in induction heating, as it directly affects the penetration depth of the heat.
●High frequencies (e.g., 100 kHz–1 MHz) are ideal for surface heating, as they create shallow penetration depths.
●Medium frequencies (e.g., 1 kHz–100 kHz) provide moderate penetration, suitable for many industrial applications.
●Low frequencies (e.g., 50 Hz–1 kHz) allow deeper heat penetration, making them ideal for through-heating larger workpieces.
Refer to standard frequency charts (such as Fig. 3) to determine the optimal frequency for your specific material and heating requirements.
The Induction Coil: What It Is
The induction coil (also called an inductor or simply a coil) is a crucial component of an induction heating system.Despite its importance, it is often
overlooked and misunderstood.
Many assume the coil is just a copper tube carrying cooling water and alternating current, but its role is far more significant. A well-designed, high-quality coil directly influences:
●Heating efficiency – Optimizing energy transfer to the workpiece.
●Heat distribution – Ensuring uniform and precise heating.
●Process control – Achieving repeatability and consistency.
●Energy consumption – Reducing waste and improving efficiency.
A properly designed induction coil is not just a component—it’s a performance driver in induction heating systems.
Ensuring Correct Process Outcomes
The heating patterns, temperatures, and heat penetration depths in an induction heating cycle are heavily influenced by the design and quality of
the induction coil. A poorly designed or improperly manufactured coil can lead to uneven heating, inefficiency, and suboptimal results.
Cost Control
A professionally designed and well-maintained coil offers:
●Longer lifespan – Reducing the frequency of replacements.
●Improved efficiency – Minimizing energy and material waste.
●Consistent performance – Ensuring precise and repeatable heating cycles.
Investing in a high-quality coil ultimately leads to better process control and lower operational costs.
A Crash Course in Induction Coils
Designing and manufacturing induction coils is a complex process that requires careful consideration of multiple factors. Here are three key
challenges in making safe and efficient coils:
1. Through-Flow Rate![]()
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Maintaining an adequate flow of cooling water through the coil is crucial, especially for high-power density coils.Insufficient flow can lead to overheating and reduced efficiency. To address this:
●A booster pump may be needed to maintain optimal water flow.
●Using high-purity water minimizes internal corrosion and extends coil life.
2. Magnetic Flux Concentrators![]()
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Flux concentrators help focus the magnetic field towards the workpiece, preventing energy loss and unwanted heating of adjacent components. They are made from:
- Laminations– High flux density, affordable, but available only in standardized sizes and require labor-intensive mounting.
- Pure ferrites– Excellent magnetic permeability but brittle and prone to breakage.
- Iron powders– Easy to shape with high flux density but susceptible to overheating. .
Mastering these factors ensures maximum efficiency, durability, and performance in an induction heating system.