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Technical Resources

Articles, guides, and industry news.

Technical Resources9 min read

Sourcing Copper Tungsten Contacts from China: What to Verify Before the First Order

China produces a large share of the world's infiltrated copper tungsten, and for switchgear OEMs and service companies outside China it is usually the price-competitive source. It is also a market where a well-designed website, an ISO certificate and a confident quote tell you very little about whether the parts will pass incoming inspection. This article is a verification list: what to ask for, what to check, and what a good answer looks like, before the first purchase order.

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Engineering Notes8 min read

Copper Tungsten Contacts for Mining and Explosion-Proof Switchgear: What Changes

Underground mining switchgear is a different animal from a utility substation breaker, and the contact materials inside it are asked different questions. The voltage is lower, the switching is far more frequent, the environment is worse, and the enclosure is certified as a whole for explosive atmospheres. This article covers where copper tungsten is used in mining and explosion-proof (Ex) switchgear, what changes compared with utility duty, and what a buyer sourcing replacement or OEM contacts for this equipment should specify.

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Technical Resources9 min read

How to Specify Copper Tungsten Contacts on a Drawing: Density, Hardness, Conductivity and Infiltration Notes

Most disputes between a switchgear OEM and a contact supplier trace back to a drawing that says "Material: CuW80" and nothing else. The supplier delivers a part that is 80 percent tungsten. The OEM's incoming inspection rejects it for low density, or the wrong hardness unit, or a braze joint with no acceptance limit to check against. Both sides are right, and the drawing is wrong.

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Technical Resources8 min read

GB/T 8320 vs ASTM B702 vs RWMA Class 10/11/12: Copper Tungsten Grade Cross-Reference

A drawing from a European OEM says "WCu 80/20". A drawing from a North American switchgear builder says "RWMA Class 12". A Chinese supplier's material certificate says "CuW80 per GB/T 8320". Are these the same material? Nearly, but not exactly, and the differences matter when the material certificate has to satisfy the drawing. This article lays out the three main designation systems side by side and explains where they line up and where they do not.

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Technical Resources8 min read

Why Type Testing Is Done at Apparatus Level, Not on the Contact Itself

A procurement engineer evaluating a new contact supplier will sooner or later ask: "Are your contacts type tested to 145 kV?" or "Can you supply contacts rated for 420 kV?" The question is reasonable. The answer, from any honest component supplier, is that contacts are not type tested and do not carry a voltage rating. The circuit breaker or GIS bay is. This article explains why that is, what a contact supplier actually is responsible for, and what evidence a buyer should ask for instead.

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Engineering Notes9 min read

CuW70 vs CuW80 for 145 kV, 245 kV and 420 kV GIS Arcing Contacts

Procurement engineers ask this in two forms. The first is "which grade do we need for 420 kV?" The second, from the supplier side, is "you have supplied 145 kV, why not 420?" Both rest on the same assumption: that voltage class maps to a copper tungsten grade. It does not, at least not directly. This article explains what actually drives the grade choice, what CuW70, CuW75 and CuW80 each give up and gain, and where the real limits sit when moving up the voltage classes.

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Engineering Notes8 min read

Can Copper Tungsten Be Electron Beam Welded? When EB Welding Is Specified and What the Alternatives Are

Short answer: yes. Copper tungsten can be electron beam welded to copper and to chromium copper, and several European HV breaker designs specify exactly that for arcing contact rods. The longer answer is that EB welding of CuW is a demanding process with a narrow window, most contact suppliers do not run it in-house, and a drawing that says "EB welded" deserves a conversation about whether the process itself is the requirement or the joint properties are.

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Engineering Notes9 min read

Cast-On vs Brazing vs Friction Welding: How CuW Arcing Contacts Are Joined to Copper

An arcing contact in an SF6 or air-blast circuit breaker is two materials doing two jobs. The copper tungsten tip takes the arc. The copper or chromium-copper shank behind it carries current, takes the mechanical load, and mounts to the mechanism. The joint between them is where most arcing contact failures start, and it is the line on the drawing that decides which supplier can quote.

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Engineering Notes9 min read

Choosing the Right AgW Grade for AC Contactors

AgW (silver tungsten) is the standard contact material for AC contactors across the low-voltage electrical apparatus market. The choice isn't whether to use AgW — it's which grade. AgW30, AgW40, AgW50, AgW70, AgW80 — five common grades cover the practical range, and each fits a specific category of contactor application.

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Engineering Notes9 min read

AgW vs CuW: When to Use Silver Tungsten vs Copper Tungsten

Silver tungsten (AgW) and copper tungsten (CuW) are sister materials in the tungsten-composite electrical contact family. Both combine a tungsten skeleton with a softer matrix metal infiltrated through powder metallurgy; both deliver arc-erosion resistance that pure copper or pure silver couldn't match. The difference between them — silver matrix vs copper matrix — sounds small but shows up in conductivity, cost, and which applications each one belongs in.

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Technical Resources8 min read

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.

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Engineering Notes9 min read

Tulip Contact Sizing: 630A, 1250A, 3150A — Choosing the Right Current Rating

Tulip contacts in MV switchgear come in a small set of standard current ratings: 630 A, 1250 A, 1600 A, 2000 A, 2500 A, 3150 A, and the higher classes used in substation feeders and transmission interfaces. The ratings aren't arbitrary — they map to standard switchgear current classes per IEC 62271 and similar specifications. Choosing the right rating for your application is mostly about matching what your breaker design or assembly calls for, but a few sourcing decisions can affect cost and service life without changing the rating.

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Technical Resources8 min read

Conductor Material Selection for MV Switchgear

The current path through MV switchgear — from cable termination through the breaker contacts to the outgoing bus — runs through conductors that have to balance three things: conductivity, mechanical strength, and arc tolerance at exposed segments. No single material wins on all three, so most switchgear current paths combine materials. This guide explains how to choose conductor material and which product to source for each segment.

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Engineering Notes8 min read

Static vs Moving Arc Contact: How a Vacuum Interrupter Pair Works

In any vacuum interrupter or vacuum circuit breaker, the contact system is built around a pair: a static (fixed) contact and a moving contact. These two parts do the work of opening and closing the circuit, surviving the arc that briefly forms between them, and carrying the breaker's continuous current during normal operation. Both contacts use the same material family (typically CuW70 or CuW80 for MV applications), but they have different mechanical and electrical roles.

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Technical Resources8 min read

Bronze Components in MV Switchgear: When to Use What

Bronze fills the spaces in MV switchgear where copper is too soft and copper tungsten is overkill — bushings, contact fingers, commutator plates, rings, and the precision machined parts that make breaker and disconnector mechanisms work. The catch is that "bronze" covers several alloy families with different properties. This guide explains which bronze alloy fits which job, and which product to source.

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Engineering Notes10 min read

The Engineer's Guide to Copper Tungsten Properties

Copper tungsten (CuW) is one of those engineering materials that sits in an unusual category — it's a composite, not an alloy, and its properties don't follow simple rules-of-mixtures from the constituent metals. For engineers specifying CuW for MV switchgear, vacuum interrupters, or other electrical contact applications, knowing how the properties behave matters for choosing the right grade and predicting service life.

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Technical Resources8 min read

Tulip Contact Selection for MV Switchgear

Tulip contacts are the plug-in connection in withdrawable MV switchgear — the multi-finger spring-loaded contacts that let you rack a breaker in and out without de-energizing the bus. Choosing the right tulip contact comes down to three things: current rating, whether you need arc resistance, and whether your application is standard switchgear or something else (like a surge arrester). This guide walks through the options.

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Engineering Notes11 min read

How to Choose the Right Copper Tungsten Grade for Vacuum Interrupters

The CuW grade selection question — CuW70 vs CuW75 vs CuW80, or whether to go higher to CuW85 or CuW90 — comes up in nearly every new VCB design project and every refurbishment program. The grades look similar on paper, the names follow a simple pattern (CuW70 = 70 wt% tungsten), and the trade-offs are straightforward in principle. In practice, the choice has cost, service life, and assembly implications that aren't always obvious to engineers new to the material family.

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Technical Resources9 min read

Copper Tungsten Components for MV Switchgear: A Sourcing Guide

If you're building or refurbishing medium-voltage switchgear, copper tungsten (CuW) shows up in more places than just the obvious arc contacts. Shielding caps, conductive rods, contact plates, guide pins — the CuW family covers a dozen distinct component types, each for a specific job inside a vacuum interrupter or switchgear assembly. This guide walks through which CuW component fits which application, so you can match the right part to your design or sourcing requirement.

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Engineering Notes9 min read

Tulip Contact vs Finger Contact: When to Use Which (MV Switchgear)

If you're sourcing contacts for an MV switchgear assembly — a withdrawable VCB, a disconnector, a cassette-style breaker — at some point the choice between tulip contact and finger contact comes up. Both are spring-loaded plug-in designs. Both handle MV current ratings. The pitch from any contact supplier will be that their version is the right answer for almost any application.

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