© 2009 Viking Preferred Service
14
Diagnostics
Theory of Induction Operation
Cooking, by definition, is the application of heat
to food. On a cooktop, very rarely is the food
heated in anything other than a cooking vessel. In
this case, the job of the cooktop becomes to heat
the vessel and allow the vessel to heat the food.
Cooking therefore, involves transferring heat to a
strategically placed cooking vessel. Two common
methods of achieving this are chemical, burning a
combustible substance such as gas, and electrical,
passing an electric current through a resistance
element.
Induction cooking, introduces a third cooking
method completely different from the other two.
Induction cooking does not involve generating
heat which is then transferred to the cooking
vessel, but rather makes the cooking vessel
the original generator of the heat source. The
induction element, inductor, can be viewed as
a powerful high-frequency electromagnet. The
electromagnetism is generated by electronics in the
inductor under the main top glass. When a good-
sized piece of magnetic material (cooking vessel)
is placed in the magnetic field that the inductor
is generating, the field induces energy into the
cooking vessel. This transfer of energy causes the
cooking vessel to become hot. By controlling the
strength of the electromagnetic field (cooktop
setting), the amount of heat being generated in the
cooking vessel can be controlled instantaneously.
How Induction Works
1. The electronics connected to the inductors
powers a coil that produces a high-frequency
electromagnetic field.
2. The electromagnetic field penetrates the metal
of the ferrous cooking vessel and sets up a
circulating electric current, which generates heat.
3. The heat generated in the cooking vessel is
transferred to the vessel’s food load.
4. Nothing outside the cooking vessel is affected
by the field as soon as the cooking vessel is
removed from the element or the element is
turned off.
There is one point about induction cooking with
current technology that needs to be made. The
cooking vessel being used must be of a ferrous
material, a magnetic will stick to it. The ferrous
material will readily sustain a magnetic field and
work with the induction system. Materials like
aluminum, copper, and Pyrex are not usable with
the induction system because they are not ferrous
and will not readily sustain a magnetic field. As a
rule of thumb, if a common refrigerator magnet
will stick to the cooking vessel, it will work with the
induction system.
Connections
to generator
Metal to be heated–
work piece
(secondary)
Inductor coil
(primary)
Magnetic field
Induced current in workpiece
Current in coil
Saucepan
Vitro
Inductors
Magnetic energy
