|
The Gridex N (Natural
convection cooling) or Gridex F (Air forced cooling) use precision cut expanded
metal as resistances elements.
These elements feature accurately controlled
mesh having solid, integral ends for mouting and connection.
____________
DESIGNING OF
ELEMENTS
____________
Type of
mesh
There are two basic mesh designs :
open mesh
: for low resistance values,
closed mesh : for
high resistance values.
Resistance
elements
Two basic designs : flat elements, C (or Grider) elements.
The choice of design is based on resistance value, cooling requirement and
mechanical rigidity.
Assembly of resistance
elements
Resistance elements are stadked together on stainless
steel threaded rods, the connection on each element to its neighbor is made by
hot spot welding.
Insulation
the insulation
between resistance elements themselves and rods is made by :
- ceramic
rings as standard application
- mica tube and washers to prevent
vibration, trepidation (this method is mostly used for dynamic braking or
railway resistor applications).
Heat dissipation
the
precision cut expanded metal resistance elements; provide a maximum heat
dissipation surface either through natural convection or air forced
cooling.
Resistance value precision
the precision cut expanded metal sheet technique can provide required
resistance value with low tolerance by varying the dimensions of the
mesh.
Flexibility
the
flexibility of expanded metal resistance allows in most cases to fit with
restricted available space as well as to optimize the weight i.e. providing low
weight with low cost per kW for continuous rating and if necessary high weight
grids for difficult cycles.
|
