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Engineering NotesSep 21, 20268 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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Engineering NotesSep 21, 20269 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 NotesSep 21, 20268 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 NotesSep 21, 20269 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 NotesJun 4, 20269 min read

CuW vs CuCr vs AgW: Which Contact Material Does Your Switchgear Need?

Three composite materials cover almost every contact application in medium- and low-voltage switching apparatus: copper tungsten (CuW), copper chromium (CuCr), and silver tungsten (AgW). They are not interchangeable. Pick the wrong one and you either overpay for performance you don't need, or you put a material into a duty it can't survive.

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Engineering NotesMay 22, 20269 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 NotesMay 18, 20269 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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Engineering NotesMay 14, 20268 min read

Brazing Copper Tungsten to Copper: Process Notes for Switchgear OEMs

In MV switchgear contact assemblies, CuW rarely stands alone. The arc-resistant CuW handles the contact face; a copper or copper-alloy carrier handles the continuous current path and mechanical mounting. Joining the two — typically by brazing — is one of the most common sub-assembly operations in switchgear OEM manufacturing.

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Engineering NotesMay 10, 20269 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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Engineering NotesMay 6, 20268 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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Engineering NotesMay 2, 202610 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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Engineering NotesApr 28, 202611 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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Engineering NotesApr 24, 20269 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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