Inductive heating and eddy currents

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SUMMARY

The discussion focuses on the design and optimization of an inductive heating system utilizing two coils to melt lead in a rotary ceramic mold. The coils operate at frequencies between 10 kHz and 100 kHz, with a preference for iron or ferrite cores to enhance magnetic field efficiency. Key considerations include the arrangement of coils to ensure proper eddy current generation, the impact of coil configuration on heating efficiency, and the necessity of maintaining a consistent magnetic field direction. The conversation highlights the importance of tuning the system for optimal performance while addressing potential electromagnetic interference (EMI) issues.

PREREQUISITES
  • Understanding of inductive heating principles
  • Familiarity with eddy currents and their behavior in conductive materials
  • Knowledge of coil design, including core materials like ferrite and iron
  • Experience with PWM (Pulse Width Modulation) control techniques
NEXT STEPS
  • Research the effects of frequency on eddy current penetration depth in metals
  • Explore the design and application of ferrite core inductors in high-frequency systems
  • Learn about electromagnetic interference (EMI) mitigation techniques in inductive heating applications
  • Investigate the use of tank circuits for resonance tuning in induction heating
USEFUL FOR

Engineers and hobbyists involved in induction heating projects, electrical engineers focusing on coil design, and anyone interested in optimizing metal melting processes using electromagnetic fields.

  • #61
artis said:
You need to look at the energy put in over time.
I did exactly that.
dB/dt * time = some J

Look at B in cos function
There are 4 distinct quadrants (that last gify shows it)
0-90deg (Bmax to zero)
90-180 (zero to Bmax)
180-270 (Bmax to zero)
270-360 (zero to Bmax)

The zero point is where dB/dt is max, as shown in that last gify.

I evaluated only the 0-90deg in my math above.
0-90 has a dB/dt, or J value from eddy (in my example, J per 25usec)
The overall J in eddy per full one cycle of frequency is the 0-90 J * 4

The push-pull in DC is technically AC.

To get same Bmax you need 100A DC, or 70.7A ACRMS

My math should be correct.
 

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