This technology makes it possible to offer resistances of power with a strong ohmic value (up to several hundred ohms ). In addition, these resistors are particularly well suited to applications which require strong tension ( constant and temporary)
THE RESISTANT THREAD
The wire diameter of the canvas can vary from 0.3 to 2mm. Different alloys are available as standard (from Constantan having a temperature coefficient equal to zero to alloys of type stainless steel or to iron-chrome-aluminum alloys ). The distance P (fig. 1) varies depending on the nature and diameter of the wire and is generally between 1 and 5 mm.
THE CHAIN WIRE
It is used to maintain the resistant wire without altering the heat exchange coefficient . A class-E glass fiber is offered as a standard model. This material has the following advantages:
- resistance to high temperatures:
- above 300 ° C in continuous service
- above 400 ° C in limited service
- Low linear thermal expansion coefficient: the length of the sheets varies very little under the action of temperature, which facilitates fixation
- excellent resistance to mechanical traction constraintswhile hot
- good resistance to pollution (except fluorine pollution)
A wide range of materials (cotton, kevlar , fiber silica ) is available for specific applications.
DIMENSIONS AND ASSEMBLY OF ELEMENTS
The fabrics are available in 2 standard widths: 160 and 250mm. However, the technique of weaving allows to adapt to all constraints. The end bands are used for fastening and can also help with the electrical insulation .
We usually use two different arrangements (fig. 2). In most cases, the canvases are arranged in rows and connected in series or in parallel or both at the same time.
- Filtering of high-power harmonics.
- High tension earthing.
- Capacitordumping at high tension .
- Infraredheating .
- Applications requiring a specific mechanical design (case of small units heatingunits ).