Learn about induction heating and all of its benefits by reading this informational document from Ambrell -- An Ameritherm Company. Visit www.ambrell.com for more information.

1. Induction
Heating Basics
The Fundamentals of Induction Heating
Induction is a fast, efficient, precise, repeatable non-contact method of heating a
workpiece that is made from electrically conductive material. The material may be
a metal such as steel, copper, aluminum, brass or a semiconductor such as
carbon, graphite or silicon carbide. To heat non-conductive materials such as
plastics or glass, induction is used to heat a metallic susceptor which then transfers
the heat to the non-conducting material.
An induction heating system typically consists of a power supply, a copper coil (the
inductor) and the workpiece to be heated. The power supply creates an alternating
current in the coil. The alternating current in the coil sets up an electromagnetic
field which generates a circulating current (or eddy current) in the workpiece. The Benefits of Induction:
eddy current flows through the resistive material of the workpiece and generates
heat. • Rapid heating
• Precise, repeatable
As mentioned, induction heating is a non-contact method of heating. The coil – heating
which is water-cooled and cool to the touch – is placed around or adjacent to the • Extended life of fixturing
workpiece, and heat is only generated by the induced current flowing in the due to precise heating
workpiece. The induced current in the workpiece flows directly adjacent to the turns • Efficient heating
of the coil. With careful coil design, precise heating can be achieved for either a • A safer, cooler work
portion of the workpiece or the entire workpiece. environment for
employees
In summary, with modern solid-state induction power supplies, embedded
microprocessor control systems and a consistent location of the workpiece in the
coil, precise, repeatable and efficient heating processes are readily achievable with
induction.
Key Factors to Consider:
• The type of metal the workpiece is made from will determine the heating rate
and power required. Steel and iron heat easily as they have higher resistivity
whereas copper and aluminum take more power due to their lower resistivity.
• The power required is determined by the type of material, size of the workpiece,
required temperature and time to temperature.
• The operating frequency of the induction heating system is based on the size of
the part to be heated. Smaller parts require a higher frequency (>50kHz) for
efficient heating, and larger parts benefit from a lower frequency (>10kHz) and
more heat penetration.
• Some steels are magnetic so both the metal’s resistivity and hysteretic
properties are used when heated with induction. When heated above the Curie
temperature (500 to 600⁰C/1000 to 1150⁰F) steel loses the magnetic properties.
However, eddy current heating provides the heating method at higher
temperatures.
. • As the temperature of the heated part rises, so does the heat losses from the
part. Radiation and convection losses from the part are a critical factor with
higher temperatures. Insulation techniques are often employed to minimize heat
losses and to reduce the power required from the Induction system.
Ambrell – An Ameritherm Company
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