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.
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.
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).
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.
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.
- Dynamic braking resistor (air forced or natural cooling).
- High fault current or high voltage Neutral Earthing Resistor.
- High power and high voltage harmonics filter resistorLoad banks.
The different type of used alloys are :
Nickel Chromium stainless steel (18% Cr, 10% Ni, AISI 304, 20% Cr, 32% Ni 32/20, 20% Cr, 63% Ni 63/20)