Silver Tungsten for LV Apparatus: A Selection Guide
Silver tungsten (AgW) is the standard contact material for low-voltage electrical apparatus, AC contactors, motor starters, relays, and LV circuit breakers. Sourcing AgW involves two decisions beyond the grade: which physical form (tip, rivet, custom) and which grade for your duty. This guide covers both, with product recommendations.
For the full range, see Silver Tungsten (AgW) Series. For the AgW grade decision specifically, see Choosing AgW Grade for AC Contactors. For when to use AgW vs CuW, see AgW vs CuW.
Form Factor: Tip, Rivet, or Custom
The physical form depends on your apparatus assembly process and volume:
- AgW Contact Tip: brazed onto a copper alloy carrier in the contactor's fixed and moving contacts. Flexible for lower-volume or higher-customization production.
- AgW Contact Rivet: a bimetallic rivet (AgW head + metal shank) with a pre-formed mounting head, riveted at assembly. The high-volume production form, riveting eliminates the brazing step.
- AgW70 Heavy-Duty Contact: AgW70 specifically for motor starters and severe-duty LV apparatus.
- AgW Custom Component: bimetallic and specialty geometries to drawing.
Decision: high-volume contactor line → riveted buttons. Lower-volume or custom geometry → brazed tips. Motor starter / heavy duty → AgW70 (in either form).
Grade by Duty
The grade follows the application's arc severity (full detail in the grade guide):
| Application | Grade |
|---|---|
| Light-duty distribution contactors, relays | AgW30, AgW40 |
| General industrial contactors | AgW40, AgW50 |
| AC-3 motor starters | AgW70 |
| AC-4 / reversing / severe duty | AgW70, AgW80 |
| LV ACBs (1000A+) | AgW70, AgW80 |
Higher tungsten content → better arc resistance, lower conductivity, higher cost. Match the grade to the duty, not the other way around.
Bimetallic Construction
For cost-optimized high-volume production, AgW + copper bimetallic contacts put the expensive silver tungsten only on the arc face, with a cheaper copper backing for the bulk current path. This is standard for riveted contacts and available for custom components. Specify the AgW thickness and backing material.
Why AgW and Not CuW for LV
AgW dominates LV apparatus because silver gives lower contact resistance than copper at the same tungsten content, which matters for continuous-current heating in compact LV devices. CuW dominates MV switchgear because arc duty there is severe enough to justify the trade-off differently, and copper's lower cost wins. The boundary is roughly 1 kV, below it, AgW; above it, CuW. See AgW vs CuW for the full comparison.
Selection Path
- What's the apparatus? Contactor / motor starter / relay / LV ACB → confirms AgW (not CuW)
- What duty? → grade (AgW30 light → AgW80 severe)
- What volume / assembly process? → form (rivet for volume, tip for flexibility)
- Cost-sensitive high volume? → bimetallic AgW + copper
Specifying Your Order
Include: AgW grade, form (tip/rivet/custom), dimensions per drawing, mounting interface, and quantity. Material follows GB/T 8320-2025 Table 6 minimums; certification per lot on request.
Related Reading
- Choosing AgW Grade for AC Contactors: grade selection detail
- AgW vs CuW: When to Use Each: material family decision
- Silver Tungsten (AgW) Series: full product range