Basic Induction Principles - Siemens EH70650 Repair Instructions

5.2

Basic induction principles

5.2.1 Overview
The use of induction heating in glass-ceramic cooking devices has
existed since 1987.
With this technique, the container is heated directly. Therefore the
cooking surface heats up only as a result of the heat transmitted from
the container to the glass, which is much lower than in conventional
systems.
The base of the container is heated by the electric currents that
circulate in its base and which are induced by a variable, medium-
frequency magnetic field generated by the inductors located
underneath the ceramic glass.
Only containers with a base made of ferromagnetic steel or iron can
be used with induction cooktops. Containers that cannot be used for
induction can be recognised by the magnet test.
Even though it is recommendable to use containers that fit the size of
the cooking zone, containers of a smaller diameter can be used
without causing notable reductions of efficiency. The cooktop control
reduces the power delivered to small containers and, if applicable,
stops supplying power when the container does not have the
minimum required diameter.
5.2.2 Operation
The power inverter transforms the 50 Hz of the power grid into an
alternating current with a frequency between 20 and 50 Hz.
Direct heating of the container base provides the induction system
with very fast heating. Likewise, the system reacts very quickly to
power level changes.
206_58300000105199_ara_en_h – 15.03.a
Induction provides very precise control of the power levels, wherefore
it allows delicate recipes to be prepared.
A temperature sensor under the glass is used in order to protect the
inductor, and it moreover allows detecting that an empty container is
being over-heated and stopping the heating process.
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