Datasheet

78 Kanthal Appliance Alloys Handbook
Surface Load
When calculating an element, voltage and
rating are normally known. The element
surface load means the rating divided by
that part of element surface, which is close
to the energised wire and therefore has an
elevated temperature. Usually a range of
surface loads and not one single figure
is listed in the mentioned tables. The choice
within the range depends upon the require-
ments for the element. It also depends upon
voltage, rating and dimensions available. A
high voltage and a low rating will result in a
thin wire, which at the same temperature
has a shorter life than a thick wire and will
therefore require a low wire surface load.
The wire surface is then found as the
ratio between rating and wire surface load.
Surface and Resistance
After having calculated the resistance in cold
state, the ratio between the surface and the
resistance is found. This ratio is listed for all
wire types and wire dimensions in the
Kanthal handbook, and the correct wire size
can therefore easily be found from these
tables.
Bash test of alloys.
Life test of 4 mm wire.