Tech Team · Kintek Solution

Induction heating frequency depends on the application, material properties, and desired heating depth. The frequency ranges from utility frequencies (50/60 Hz) for large-scale melting to ultra-high frequencies (up to 500 kHz) for precise, shallow heating. Lower frequencies penetrate deeper into materials, while higher frequencies are ideal for surface heating. The choice of frequency is influenced by factors like material type, workpiece size, heating speed, and cost considerations. Understanding the relationship between frequency, skin depth, and heating efficiency is critical for selecting the appropriate induction heating system.

Key Points Explained:

1. Frequency Ranges for Induction Heating

   • Utility Frequency (50/60 Hz): Used for large-scale industrial applications like melting metals in induction furnaces. Suitable for deep penetration heating due to low frequency.
   • Intermediate Frequency (500 Hz to 10 kHz): Ideal for medium-depth heating applications, such as hardening larger components or forging.
   • High Frequency (100 kHz to 500 kHz): Best for surface heating, small parts, or applications requiring precise, shallow heating, such as brazing or hardening thin layers.

2. Skin Depth and Frequency Relationship

   • The skin depth effect determines how deeply the alternating current penetrates the material.
     • Higher frequencies (e.g., 100–500 kHz) result in shallow penetration, making them suitable for surface heating.
     • Lower frequencies (e.g., 50 Hz–10 kHz) allow deeper penetration, ideal for bulk heating or melting.
   • The formula for skin depth (δ) is:
     [ \delta = \sqrt{\frac{2\rho}{\omega\mu}} ]
     Where:
     • (\rho) = resistivity of the material
     • (\omega) = angular frequency ((2\pi f))
     • (\mu) = magnetic permeability of the material

3. Material and Application Considerations

   • Material Type: Materials with high magnetic permeability (e.g., ferrous metals) heat more efficiently at lower frequencies. Non-magnetic materials (e.g., aluminum, copper) require higher frequencies for effective heating.
   • Workpiece Size: Smaller workpieces or thin layers benefit from higher frequencies, while larger volumes require lower frequencies for uniform heating.
   • Heating Speed: Higher frequencies enable faster heating for surface applications, while lower frequencies are better for slower, deeper heating.

4. Cost and Efficiency Factors

   • Equipment Cost: Higher-frequency systems (e.g., 100–500 kHz) are generally more expensive due to complex power electronics. Lower-frequency systems (e.g., 50 Hz–10 kHz) are more cost-effective for large-scale applications.
   • Energy Efficiency: The choice of frequency affects energy consumption. Matching the frequency to the application ensures optimal efficiency and minimizes waste.

5. Practical Examples of Frequency Selection

   • Melting Metals in Induction Furnaces: Low frequencies (50 Hz–10 kHz) are used for large-scale melting, as they provide deep penetration and stirring effects.
   • Surface Hardening: High frequencies (100–500 kHz) are ideal for hardening thin surface layers of steel components.
   • Brazing or Soldering: Intermediate frequencies (500 Hz–10 kHz) are often used for joining small components with controlled heating.

6. Technical Principles Behind Induction Heating

   • Induction heating relies on electromagnetic induction, where an alternating current in a coil generates a transient magnetic field. This field induces eddy currents in the workpiece, producing heat due to the material's resistance.
   • The frequency of the alternating current determines how quickly the magnetic field changes, influencing the heating depth and efficiency.

7. Summary of Key Frequency Applications

   Frequency Range	Applications
   50–60 Hz	Large-scale melting, deep heating
   500 Hz–10 kHz	Forging, medium-depth heating, brazing
   100–500 kHz	Surface hardening, small parts, precise heating

By understanding these principles and factors, you can select the appropriate frequency for your induction heating needs, ensuring optimal performance, efficiency, and cost-effectiveness.

Summary Table:

Frequency Range	Applications
50–60 Hz	Large-scale melting, deep heating
500 Hz–10 kHz	Forging, medium-depth heating, brazing
100–500 kHz	Surface hardening, small parts, precise heating

Need help choosing the right induction heating frequency? Contact our experts today for tailored solutions!