Bronze Stud Connectors for Transformers | Electrical Transformer Stud Connectors
Conex Casting manufactures precision bronze stud connectors for transformers and electrical transformer stud connectors used in power distribution systems, substation equipment, and high-voltage transformer bushings. Our cast bronze and copper alloy transformer connectors are produced to exact engineering specifications and comply with IEC, ASTM, and BS standards. Designed for both internal and external transformer applications, Conex Casting supplies OEMs, EPC contractors, power utilities, and electrical distributors globally. Starting at $16.90/Kilogram
Product Overview: Bronze & Copper Transformer Stud Connectors
Transformer stud connectors — also known as transformer stud terminals, transformer bushing connectors, and transformer terminal pads — are critical conducting components that establish the electrical interface between transformer coil windings and the external power network. Conex Casting produces these components through gravity die casting and sand casting in LG2 bronze, C93200, C95400, and high-conductivity copper alloys, ensuring dimensional consistency, low contact resistance, and long service life in harsh electrical environments.
Internal Transformer Connectors (Copper Cast)
Internal transformer stud connectors are mounted inside the transformer tank and provide the coil-to-bushing electrical continuity. Cast from high-conductivity copper (C11000 / ETP copper), these connectors are machined smooth on both mating faces to ensure maximum contact surface area. Key related terms: internal bushing connector, transformer coil terminal, copper cast connector, transformer LV terminal, internal transformer link, copper bushing stud, substation transformer fitting, coil-to-bushing contact, internal terminal block, transformer winding lug. Conex Casting machines these to customer-supplied dimensional drawings with tolerances to ±0.05 mm, making them a direct-fit replacement for OEM bushing assemblies.
External Bronze Stud Connectors (Tin-Plated)
External transformer stud connectors are mounted on the outside of the transformer tank or pad-mounted transformer body and facilitate the connection of outgoing HV/LV cables to the transformer bushing. Cast from LG2 bronze (C83600) and finished with electrodeposited tin plating for oxidation resistance, these connectors are available in connector pad sizes from 1-1/8″ to 4″ (28 mm to 100 mm). Key related terms: external bushing pad, transformer terminal connector, bronze stud terminal, HV transformer connector, LV bushing terminal, tin-plated transformer fitting, external connecting pad, distribution transformer lug, outdoor transformer connector, external transformer terminal block. These are machined with a smooth dual-sided finish for maximum electrical contact.
Transformer Bushing Connectors for Distribution Transformers
Distribution transformer bushing connectors are used at 11 kV, 33 kV, and 66 kV transformer bushings to connect overhead lines or cable tails. Conex Casting’s bronze bushing connectors are engineered to resist corona discharge and localized heating. Relevant terms: cable-to-bushing connector, outdoor distribution fitting, overhead line transformer terminal, 11 kV transformer connector, pad-mounted transformer terminal, epoxy-insulated bushing pad, distribution substation fitting, ANSI C57.12 bushing stud, transformer HV terminal block, transformer LV spade connector. These components are routinely used in rural distribution networks and utility substation equipment.
Power Transformer Terminal Pads and Studs
Transformer terminal pads and stud assemblies are used on large power transformers (33 kV–400 kV) for current ratings from 200 A to 5000 A. Conex Casting provides custom-engineered pads in bronze and silicon bronze grades to match OEM drawings. Related terms: power transformer terminal block, high-current bushing connector, large transformer terminal pad, transformer stud assembly, 400 kV transformer fitting, power substation terminal, EHV transformer connector, transformer connecting flange, ONAN transformer terminal, transformer bushing extension. These products serve the heavy utility and power generation sectors including steam plants, hydro stations, and solar farm step-up transformers.
Substation Equipment Connectors and Transformer Fittings
Beyond transformer-specific applications, Conex Casting’s bronze cast connectors are used across switchgear, disconnect switches, and bus duct connections in substations. These connectors see continuous duty at elevated temperatures and must maintain dimensional stability over decades. Connected terms: substation bronze casting, electrical switchgear connector, bus bar clamp, GIS substation fitting, switchgear terminal block, SF6 equipment connector, capacitor bank terminal, SCADA-ready substation fitting, IEC 62271 compliant connector, transformer incoming terminal. Conex Casting’s ISO 9001:2015 certified foundry ensures traceability and batch consistency for all substation-grade castings.
Custom Cast Transformer Connectors to OEM Drawings
Conex Casting accepts custom orders for transformer connectors manufactured to customer drawings or samples, including unusual alloy grades, special coatings (silver plating, nickel plating), and large production runs with statistical process control documentation. Related technical terms: custom bronze casting, OEM transformer parts, transformer spare parts manufacturer, bushing stud casting supplier, IEC 60076 transformer accessories, ASTM B505 bronze casting, centrifugal cast transformer bushing, investment cast transformer fitting, CNC machined transformer terminal, prototype transformer connector. MOQ is negotiable for repeat OEM programs.
Key Features of Conex Casting Transformer Stud Connectors
- Cast from high-conductivity copper (C11000) and LG2 bronze (C83600) for optimal electrical and mechanical performance
- Dual-sided machined finish for maximum contact surface area and minimum contact resistance
- Tin-plated external connectors for resistance to oxidation, galvanic corrosion, and tropical humidity
- Custom manufactured to OEM dimensions, ANSI, IEC, or BS drawings
- Size range: 1-1/8″ to 4″ (28 mm to 100 mm) connecting pad diameter
- Current ratings: 200 A to 5000 A (application-dependent)
- Compatible with distribution (11–66 kV) and power transformers (up to 400 kV)
- Available in bulk or project-specific quantities with material test certificates (MTC)
High-Conductivity Alloy Grades
Internal connectors use pure electrolytic tough pitch (ETP) copper (C11000 / UNS C11000) with conductivity exceeding 99.9% IACS, ensuring coil-to-bushing current transfer without resistive loss. External connectors use leaded gunmetal (LG2 / C83600) for the combination of corrosion resistance and machinability needed in outdoor-exposed transformer terminals. Silicon bronze (C65500) is also offered for marine and coastal substation environments. Relevant terms: ETP copper casting, leaded gunmetal LG2, C83600 bronze, silicon bronze connector, IACS conductivity transformer, C11000 copper connector, high-conductivity bushing, copper alloy transformer fitting, free-machining bronze, electrical grade copper.
Precision Machining and Surface Finish
All transformer connector mating surfaces are CNC-turned to a surface finish of Ra 1.6 µm or better on both sides of the connecting pad, ensuring full face-to-face contact when bolted to the bushing flange. Thread forms (BSP, NPT, UNC, metric) are cut to tolerance class 6H/6g. Related terms: CNC machined bronze, surface finish Ra 1.6, transformer bushing machined face, thread tolerance 6H/6g, flat face connector, bolted transformer terminal, dimensional accuracy casting, machined bronze pad, transformer connector flatness, precision turned connector.
Tin Plating and Corrosion Protection
Electrodeposited tin plating (10–25 microns per ASTM B545) on external bronze connectors prevents oxidation of the base metal, maintains low contact resistance over years of service, and resists the sulfurous and chloride-rich environments common near coastal substations. Conex Casting also offers hot-dip tin coating and nickel plating options for demanding environments. Related terms: tin-plated bronze connector, ASTM B545 tin plating, electrodeposited tin, corrosion-resistant transformer fitting, nickel-plated bushing connector, anti-oxidation bronze, tropical grade transformer fitting, salt-spray resistant connector, IEC 60068-11 corrosion test, outdoor-rated transformer terminal.
Dimensional Customization and OEM Compatibility
Conex Casting reverse-engineers existing transformer connectors from OEM samples or 2D drawings and produces precise casting patterns for production runs. All critical dimensions (bore diameter, pad diameter, stud thread, face flatness) are verified on CMM equipment before dispatch. Terms: custom transformer casting, reverse engineering bronze parts, OEM-compatible transformer terminal, certified dimension report, CMM inspection, first article inspection (FAI), dimensional compliance certificate, transformer spare parts casting, bronze casting to drawing, ISO 2768 tolerance.
Electrical Testing and Quality Verification
Each batch of transformer connectors undergoes contact resistance measurement (micro-ohm bridge), hardness testing (Brinell HB), chemical composition analysis (OES spectroscopy), and dimensional inspection. Optional pull-out tests and salt-spray tests are available upon request. Related terms: contact resistance micro-ohm, transformer connector testing, Brinell hardness bronze, OES chemical analysis, electrical casting inspection, quality test certificate transformer, material conformance report, IEC 60076-1 transformer accessories testing, bronze casting mechanical properties, batch traceability certificate.
Technical Specifications
| Parameter | Internal Connector (Copper) | External Connector (Bronze) |
|---|---|---|
| Base Material | Electrolytic Copper C11000 | LG2 Bronze C83600 |
| Conductivity | >99.9% IACS | 15% IACS (structural grade) |
| Surface Finish (Mating Face) | Ra 1.6 µm (CNC machined) | Ra 1.6 µm (CNC machined) |
| Plating | None / optional tin or silver | Tin 10–25 µm (ASTM B545) |
| Pad Size Range | Custom / 25–120 mm dia. | 1-1/8″ to 4″ (28–100 mm) |
| Stud Thread Options | M10 to M36 / UNC 3/8″–1-1/2″ | M10 to M36 / UNC 3/8″–1-1/2″ |
| Casting Process | Sand Casting / Gravity Die | Sand Casting / Gravity Die |
| Hardness | HB 40–60 | HB 60–85 |
| Tensile Strength | 220–250 MPa | 240–290 MPa |
| Operating Temperature | -40°C to +180°C | -40°C to +120°C |
| Current Rating (typical) | 200 A – 5000 A | 200 A – 3000 A |
| Voltage Rating | Up to 400 kV (bushing-level) | Up to 400 kV (bushing-level) |
| Price | $16.90/Kilogram | $16.90/Kilogram |
| Availability | In Stock / Made to Order | In Stock / Made to Order |
Alloy Grade Comparison Table
| Alloy | UNS No. | Cu % | Sn % | Pb % | Zn % | Application |
|---|---|---|---|---|---|---|
| ETP Copper | C11000 | 99.9+ | — | — | — | Internal transformer connector |
| LG2 / Gunmetal | C83600 | 85 | 5 | 5 | 5 | External transformer connector |
| Phosphor Bronze | C51000 | 94.8 | 5 | — | — | High-load terminal pad |
| Silicon Bronze | C65500 | 97 | — | — | 1.5 | Marine/coastal substation |
| Aluminium Bronze | C95400 | 85 | — | — | — | High-temperature terminal |
International Material Equivalent Table
| Grade | USA (ASTM/UNS) | UK (BS) | Germany (DIN) | Japan (JIS) | ISO |
|---|---|---|---|---|---|
| ETP Copper | C11000 / ASTM B187 | BS 1400 PB2 | CW004A / CuETP | C1100 | ISO 1337 Cu-ETP |
| LG2 Bronze | C83600 / ASTM B505 | BS 1400 LG2 | Rg5 / CuSn5Pb5Zn5 | CAC406 | ISO 1338 CuSn5Pb5Zn5 |
| Phosphor Bronze | C51000 / ASTM B139 | BS 2870 PB102 | CW451K | C5111 | ISO 196 CuSn5 |
| Silicon Bronze | C65500 / ASTM B98 | BS 2870 CS101 | CW116C | C6561 | ISO 196 CuSi3Mn |
Product Types and Variants
| Product Type | Material | Location | Size Range | Finish | Application |
|---|---|---|---|---|---|
| Internal Transformer Stud Connector | C11000 ETP Copper | Inside transformer tank | 25–120 mm pad dia. | Machined, smooth | Coil-to-bushing link |
| External Bronze Stud Connector | LG2 Bronze C83600 | Outside transformer body | 1-1/8″ to 4″ | Tin-plated, machined | Bushing-to-cable link |
| High-Current Terminal Pad | C95400 / C51000 | HV bushing terminal | Custom | Nickel or silver plated | Power transformer 132–400 kV |
| Coastal Grade Connector | C65500 Silicon Bronze | External, marine zone | 28–100 mm | Tin-plated + sealed | Coastal/offshore substation |
| Custom OEM Transformer Fitting | As specified | Any | Drawing-based | As required | Specific OEM replacement |
Applications in Industry
| Industry / Application | Connector Type | Voltage Level | Notes |
|---|---|---|---|
| Power Utilities & Grid Substations | Internal + External | 33 kV – 400 kV | Transmission transformer terminals |
| Distribution Networks (Pole/Pad-Mounted) | External Bronze | 11 kV – 33 kV | LV/HV bushing connection |
| Industrial Facilities (Steel, Mining, Cement) | Internal + HV Pad | 11 kV – 132 kV | Captive power transformers |
| Renewable Energy (Solar/Wind Farm) | External Bronze | 33 kV – 132 kV | Step-up transformer terminals |
| EPC / Turnkey Projects | Custom OEM | As designed | Full project supply |
| Transformer OEM Manufacturers | Internal Copper | All ratings | Factory-fitted internal connectors |
| Repair & Maintenance (Transformer Refurbishment) | Internal + External | All ratings | Replacement for worn terminals |
| Railway Traction Substations | Internal Copper | 25 kV AC / 1500 V DC | Traction transformer fittings |
Manufacturing Process
Conex Casting produces transformer stud connectors through a quality-controlled foundry process. The process begins with certified raw material intake — ETP copper ingot (ASTM B5) or LG2 bronze ingot (ASTM B505) — each tested by OES spectrometer for chemical compliance before charging. For gravity die casting, permanent steel dies are pre-heated to 250–300°C and the melt is poured at 1100–1200°C (copper) or 980–1050°C (bronze) under controlled conditions to eliminate shrinkage porosity and gas inclusions. For larger or complex internal connectors, sand casting (green sand or shell mold) provides the dimensional flexibility required. After solidification and shakeout, castings undergo shot blasting and are moved to the CNC machine shop, where faces, bores, and threads are machined to drawing tolerances. Internal connectors are deburred and cleaned; external connectors pass to the electroplating line for tin plating (alkaline or methane sulfonate bath, 10–25 µm). Each connector is stamped with heat number, alloy grade, and Conex batch code for full traceability. Final inspection includes dimensional check, hardness test, visual inspection, and contact resistance measurement before packaging and dispatch.
Quality Standards and Certifications
| Standard / Certification | Scope |
|---|---|
| ISO 9001:2015 | Quality management system — foundry and machining operations |
| ASTM B505 | Copper alloy continuous castings specification |
| ASTM B187 | Copper bar, rod, shape & forgings specification |
| ASTM B545 | Tin plating specification for electrodeposited coatings |
| IEC 60076-1 | Power transformers — general requirements (accessories) |
| BS 1400 LG2 | British Standard — leaded gunmetal casting alloy |
| IS 318 | Indian Standard — leaded tin bronzes and gunmetals for castings |
| RoHS Compliant | Restriction of Hazardous Substances (alternate Pb-free alloys available) |
| Material Test Certificate (MTC) | 3.1 or 3.2 inspection certificate per EN 10204 |
Why Choose Conex Casting for Transformer Stud Connectors?
| Factor | Conex Casting Capability |
|---|---|
| Experience | Decades of specialization in bronze and copper electrical castings for the global power sector |
| Alloy Expertise | Full range: ETP Copper, LG2, Phosphor Bronze, Silicon Bronze, Aluminium Bronze |
| Custom Engineering | Pattern development, OEM reverse engineering, prototype-to-production in 4–6 weeks |
| Certification | ISO 9001:2015; EN 10204 3.1/3.2 MTCs available; third-party inspection accepted |
| Price | $16.90/Kilogram — competitive ex-works India pricing for global export |
| Global Supply | Exports to USA, UK, Europe, Middle East, Africa, Southeast Asia, Australia |
| Lead Time | Standard: 3–5 weeks; Express: 2 weeks with tooling on hand |
| Minimum Order Quantity | Low MOQ for trials; volume pricing for OEM programs |
| Traceability | Full batch traceability — heat number, OES analysis, dimensional records |
Related Products — Electrical Castings by Conex Casting
Explore our full range of electrical casting products:
- Aluminium Hotline Clamps — overhead line maintenance connectors for energized conductors
- Bronze Wedge Connectors — cast bronze wedge-type tap connectors for overhead distribution lines
- Aluminium Wedge Connectors — lightweight aluminium alloy bolted wedge connectors
- Bronze Acorn Clamps — ground rod clamps and acorn-style grounding connectors
- Aluminum Vise Connectors — aluminium vise-grip style ground connectors
- Bronze Bolted Stirrup Clamps — heavy-duty bronze stirrup clamps for cable-to-bus connections
- All Electrical Castings — full product category index
Multilingual Equivalent Terms
| Language | Term 1 | Term 2 | Term 3 |
|---|---|---|---|
| Spanish | Conectores de espiga para transformadores | Terminales de bronce para transformador | Conectores de buje para transformador |
| Russian | Бронзовые шпилечные коннекторы для трансформаторов | Клеммы трансформатора из бронзы | Соединители ввода трансформатора |
| French | Connecteurs à goujon en bronze pour transformateurs | Bornes de transformateur en bronze | Raccords de traversée de transformateur |
| Portuguese | Conectores de pino de bronze para transformadores | Terminais de bucha para transformador | Conector de bronze para transformador elétrico |
| Italian | Connettori a perno in bronzo per trasformatori | Terminali di trasformatore in bronzo | Raccordi di passante per trasformatori |
Frequently Asked Questions
An internal transformer stud connector is mounted inside the transformer tank and provides the electrical connection from the winding coil to the transformer bushing. An external bronze stud connector is mounted on the outside of the transformer body and connects the bushing to outgoing cables or overhead lines. Internal connectors are typically made from high-conductivity copper; external connectors are made from bronze with tin plating for outdoor corrosion resistance.
Internal transformer connectors are cast from Electrolytic Tough Pitch (ETP) copper, UNS C11000, with conductivity exceeding 99.9% IACS. This ensures minimum resistive loss between the coil and the bushing. Alternative grades such as C10100 (oxygen-free copper) are available for ultra-low-loss applications.
Conex Casting’s standard external bronze stud connectors cover connecting pad diameters from 1-1/8″ (approximately 28 mm) to 4″ (approximately 100 mm). Custom sizes outside this range are available through our pattern development service, with lead times of 4–6 weeks for new tooling.
Yes. Conex Casting’s transformer stud connectors are manufactured to comply with IEC 60076 (power transformers accessories) and can be produced to ANSI C57.12 bushing stud dimensions. We accept customer drawings and can match any OEM bushing pad layout.
Yes. Material Test Certificates (MTC) per EN 10204 3.1 (manufacturer-certified) and 3.2 (third-party certified) are available. Each MTC includes OES chemical analysis, Brinell hardness, tensile strength, and confirmation of plating thickness for tin-plated external connectors.
There is no fixed minimum order quantity for standard sizes. For custom-engineered connectors, MOQ is typically 50–100 kg (approximately 20–50 pieces depending on size) to amortize tooling costs. Volume pricing applies for OEM programs above 500 kg.
For new patterns/tooling: 4–6 weeks from drawing approval. For repeat orders using existing patterns: 3–4 weeks. Express production (2 weeks) is possible for existing patterns with prior notice. Shipping time from India to USA/Europe is typically 2–3 weeks by sea or 3–5 days by air freight.
Yes. Conex Casting regularly supplies transformer stud connectors as part of EPC electrical package orders. We can provide bulk quantities, project-specific markings, packing lists, and documentation packages (MTCs, dimensional reports, inspection certificates) to meet project QA requirements.
We export to the USA, United Kingdom, Germany, France, UAE, Saudi Arabia, South Africa, Nigeria, Australia, Singapore, Malaysia, Bangladesh, and across Southeast Asia and Latin America. All exports comply with applicable national import regulations and include ECTN/COO as required.
Yes. In addition to standard tin plating, Conex Casting offers electroless nickel plating (ENP, 25–75 µm) and silver plating (5–25 µm) on bronze transformer connectors for high-temperature bushing applications, GIS switchgear interfaces, or applications requiring enhanced corrosion performance beyond tin plating.
Request a Quote for Bronze Transformer Stud Connectors
In Stock & Made to Order | $16.90/Kilogram | ISO 9001:2015 Certified | MTCs Available | Ships Worldwide
Email: sales@conex-casting.com Get a Quote in 24 Hours