Contact Materials and Contact Parts are manufactured in a wide variety of Contact and Carrier Material combinations as per customer’s specifications.

Quality of the products and production processes is strictly monitored to ensure conformance to specifications. The quality Assurance Systems ensures complete traceability of all product batches within the framework of ISO 9001 : 2000 standards.

‘COPTUNS’ ARCING CONTACT MATERIAL :

MODISON offers high erosion resistant Copper Tungsten material produced by Powder Metallurgy wherein sintered skeleton of Tungsten is impregnated with Copper. The erosion pattern of this material is far superior to materials produced by other production techniques. This material maintains quite regular shape under extreme arcing conditions and has only uniform roughening effect without cracks and burn-off droplets.
The Tungsten skeleton is protected by impregnated Copper as it provides evaporative cooling effect in extreme arcing conditions, thereby protecting and limiting the temperature rise of the skeleton and preventing disintegration. The grain size of Tungsten powder has considerable influence on arc erosion behaviour of Copper Tungsten Contact Materials. Grain size of Tungsten is optimized to meet customer’s product needs in order to have low uniform erosion rates and burn-out patterns. All contact materials are produced by impregnation liquid phase sintering (wet sintering of presintered skeleton). Although laboratory tests indicate that minimum erosion occurs when the Tungsten grain size is between 2 and 8 µm, materials made of other grain sizes have also given superior performance in practice. The tungsten content in the composite does influence contact performance. Materials with particularly high Tungsten content consisting of fine powders, quickly develop cracks on the surface when subjected to repeated thermal and mechanical shocks. This can lead to parts of Tungsten skeleton’s disintegration and impairing the function of the Circuit Breaker. On the other hand materials which have a slightly higher Copper content (25~30%Cu) show a regular erosion pattern with only a slight roughening of the surfaces.
The final chemical composition can only be maintained within certain limits due to impregnation method of sintering. Accordingly instead of fixed data, it is only possible to give production dependent ranges for the mechanical and electrical characteristics although this does not affect the most important functional characteristics –its erosion behaviour to any significant degree.

Typical Forms Available:

• Contact Pins/Plugs/Rods with Electron Beam Welded Tips
  
• Contact Tulips with EB Welded CuCr/CuCrZr Base bodies.
  
• Contact Tulips with pre-stressed contact fingers
  
• Contact Tubes
  
• Arcing Rings
  
• Shaped Contacts (Warm/Cold forged) & Contact Fingers with
  brazed Tips

Applications:

• SF-6 Circuit Breaker
  
• Load Break Switches
  
• Transformer Step Switches (OLTC)
  
• Resistance Welding Electrodes
  
• Spark Erosion Electrodes

MAIN CONTACTS:

We offer complete range of continuous current carrying Main Contacts, manufactured as per customer’s drawings & specifications in Copper/OFC, Copper Chromium, Copper Chromium Zirconium, Silver Bronze, Silver bearing Copper etc.
Plant is well equipped with CNC Turning and Machining Centers having full fledged in-house facility for silver plating up to 100µm thickness. Silver plating can also be done selectively only on functional area as per customers requirement. All facilities under one roof helps in quick delivery of parts ready-to-assemble on the breaker pole.

Joining Technology :

Electron Beam Welding:
Generally Modison offers Arcing Contacts where the Copper Tungsten Tip is joined with the carrier by Electron Beam Welding. This process of welding offers the most reliable joint and minimum heat affected zone (softening of the base part) and thereby maintaining joint properties very close to parent metal properties. The small localized is further improved by reshaping and cold working. EB welding is also especially suitable for joining dissimilar carrier materials such as steel to Cu/Cu/Cr.

Cast On (Direct bonding of Copper):

The melting-on (Casting-on) of the Copper carrier metal on pre-sintered Copper Tungsten provides a perfect bonding as can be seen in the microstructure photograph. Thus jointless connection is produced between Copper Tungsten face and Copper carrier. Initially the Cast-on moulded blank in “as cast” condition is soft and is further cold worked & strengthened using special tooling where the Copper Tungsten tip is protected thereby only the melted-on carrier part is cold worked. MODISON is well equipped with a range of hydraulic presses up to 4000 KN and master tools to carry out these operations. By a special combined melt-on & impregnation process direct bonding of Copper Tungsten with steel is also produced.

Brazing:

Only small Copper Tungsten parts are brazed using Silver Brazing Alloys in atmosphere controlled Brazing Furnace/Flame/Induction Brazing.