2,808
edits
Changes
→Copper–Tungsten (CUWODUR) Materials
according to the end application ''(Figs. 2.138 – 2.141) (Table 2.39)''. To increase the wettability of the tungsten skeleton by copper a small amount of nickel < 1 wt% is added to the starting powder mix.
W/Cu materials exhibit a very high arc erosion resistance ''<xr id="tab:tab2.40"/> (Table 2.40)''. Compared to silver–tungsten materials they are however less suitable to carrypermanent current.
With a solid tungsten skeleton as it is the case for W/C infiltrated materials with 70-85 wt% tungsten the lower melting component copper melts and vaporizes in the intense electrical arc. At the boiling point of copper (2567°C) the still solid tungsten is efficiently “cooled” and remains pretty much unchanged.
The main application areas for CUWODUR materials are as arcing contacts in load and high power switching in medium and high voltage switchgear as well
as electrodes for spark gaps and over voltage arresters ''<xr id="tab:tab2.41"/> (Table 2.41)''.
'''Table 2.39: Physical Properties of Copper–Tungsten (CUWODUR) Contact Materials'''
[[File:Micro structure of W Cu 80 20 H.jpg|right|thumb|Micro structure of W/Cu 80/20 H]]
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</div>
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<figtable id="tab:tab2.40">
'''Table 2.40: Contact and Switching Properties of Copper–Tungsten (CUWODUR) Contact Materials'''
<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s12">Material/ DODUCO- Designation</p></td><td><p class="s12">Properties</p></td></tr><tr><td><p class="s12">W/Cu F</p><p class="s12">CUWODUR F</p></td><td><p class="s12">Very high arc erosion resistance,</p><p class="s12">Uniform erosion pattern after high operation frequency, Very high mechanical strength,</p><p class="s12">Highly resistant against thermal and mechanical shock</p></td></tr><tr><td><p class="s12">W/Cu G</p><p class="s12">CUWODUR G</p></td><td><p class="s12">Very high arc erosion resistance, Very high mechanical strength,</p><p class="s12">Highly resistant against thermal and mechanical shock.</p></td></tr><tr><td><p class="s12">W/Cu H</p><p class="s12">CUWODUR H</p></td><td><p class="s12">Very high arc erosion resistance, very high mechanical strength, Especially high resistance against thermal and mechanical shock.</p></td></tr></table>
</figtable>
<figtable id="tab:tab2.41">
'''Table 2.41: Application Examples and Forms of Supply for Tungsten– Copper (CUWODUR) Contact Materials'''
<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s12">Material</p></td><td><p class="s12">Application Examples</p></td><td><p class="s12">Form of Supply</p></td></tr><tr><td><p class="s12">W/Cu F</p></td><td><p class="s12">Transformer tap changers,</p><p class="s12">Medium voltage circuit breakers</p></td><td><p class="s12">Contact tips, formed parts, brazed</p><p class="s12">and welded contact parts</p></td></tr><tr><td><p class="s12">W/Cu G</p></td><td><p class="s12">Overvoltage arresters with spark gap,</p><p class="s12">Medium voltage circuit breakers, Medium voltage power switches, High voltage power switches and circuit breakers</p></td><td><p class="s12">Contact tips, formed parts, brazed</p><p class="s12">and welded contact parts; Contact tulips, rods and tubes</p></td></tr><tr><td><p class="s12">W/Cu H</p></td><td><p class="s12">High voltage power switches and circuit</p><p class="s12">breakers for very high short circuit currents</p></td><td><p class="s12">Welded contact parts; Contact tulips,</p><p class="s12">rods</p></td></tr></table>
</figtable>
==References==
[[Contact Materials for Electrical Engineering#References|References]]
