TRANSFORMER INSULATION MATERIALS
THE GUND COMPANY IS ONE OF THE WORLD'S MOST RELIABLE MANUFACTURERS AND FABRICATORS OF INSULATION MATERIALS FOR ELECTRO-MECHANICAL APPLICATIONS IN THE TRANSFORMER MARKET.
Even though the primary components (core, coil, leads, and others) are similar in the dry type transformer (DTT) and liquid filled transformer (LFT). The insulation can be quite different. DTTs mainly utilize safety-certified CSA and UL-recognized high-temperature insulation materials. In contrast, LFTs use oil and high dielectric strength cellulose-based insulation materials like paper, pressboard, and wood.
The Gund Company manufactures a wide range of Transformer insulation materials & components for the various transformer types. This includes Dry Type Transformer Insulation and Liquid Filled Transformer Insulation. Our application engineering expertise can help our customers understand their insulation material selection and component design options, from large liquid-filled transformers to dry type distribution transformers to low-voltage electronics transformers.
DRY TYPE TRANSFORMERS
MOST FREQUENTLY USED IN APPLICATIONS WHERE THE USE OF DIELECTRIC OIL IN THE TRANSFORMER DESIGN IS NOT ALLOWED.
In contrast to liquid filled transformers that use dielectric liquids to insulate and cool the transformer’s windings, dry type transformer designs must use higher-temperature insulation materials in order to operate without the use of cooling liquids. Most dry type transformers in North America are certified to UL and CSA-recognized insulation systems.
The Gund Company is a vertically integrated manufacturer of these high-temperature insulation materials for dry type transformer insulation, including materials rated at 155 °C, 180 °C, and 220 °C that have explicitly been tested per UL 1446 for chemical compatibility with a long list of UL recognized insulation systems. The Gund Company offers a variety of insulation components for the following types of dry type transformers.
Core Insulation
- G-Flex YT510, high temperature Aramid paper
- G-Flex APA, flexible laminate Aramid/PET/Aramid
- Filament Wound Tubes, glass/epoxy
- Gundply, B-Stage
- N200F, Flexible GPO-1
LAYER WOUND, DRY TYPE TRANSFORMERS
Also known as barrel wound transformers, layer-wound transformers are most commonly used in low-voltage (<600v Class) applications. Layer-wound units are so-called because the coil is made by wrapping a layer of conductor around an insulated winding form and then wrapping a layer of insulation over the conductor.
The coil is built by wrapping a layer of conductor and then a layer of insulation in successive layers per the design. This design typically relies on high-temperature spacer sticks called “dogbones” to create the air-cooling passages. Between the primary and secondary coils, it is common to have a flexible insulation layer such as Nomex® or YT510 Aramid Paper or even a flexible glass polyester laminate such as Grade N200F or Grade FHT.
- Filament Wound Core Tubes
- Winding Forms
- Layer “Turn” Insulation
- Layer Insulation Tape
- “Dogbones” – Axial Spacer Sticks
- Yoke Insulation
- Coil Support Blocks
- Wedges, Shims, & Filler
- Lead Supports, Spacers, & Clamps
- Fuse Boards
- Terminal Boards
- Lead Insulation – Sleeving
- Phase Barriers
- Fasteners – Rods & Nuts
- Enclosure Gaskets
DISC WOUND, DRY TYPE TRANSFORMERS
Compared to barrel or layer wound transformers, disc wound transformer designs are often designed for higher voltage applications. The conductor is wrapped around the coil in a fashion that makes the coil appear to be a series of stacked discs, separated by airflow gaps, giving disc wound transformers their name.
These units use either radial spacers or winding combs to form the conductor support and winding path around the coil while providing airflow gaps through the coil. These radial spacers and winding combs are made with high-temperature (130 °C, 155 °C, 180 °C, or 220 °C) glass polyester insulation material such as NEMA GPO-3, NEMA GPO-1 (Grades: N155, N180, N220, SG-200, or HST-II).
- Standoff Insulators
- Bus Support Angles & Channels
- Filament Wound Core Tubes
- Winding Forms
- Conductor Wrap
- Winding Combs
- Axial Radial Spacers
- Spacer Sticks “Dogbones”
- Yoke Insulation
- Coil Support Blocks
- Wedges, Shims, Filler
- Lead Supports, Spacers, & Clamps
- Fuse Boards
- Terminal Boards
- Lead Insulation – Sleeving
- Phase Barriers
- Fasteners – Rods & Nuts
CAST COIL TRANSFORMERS
In most designs, the vacuum molding process used to create the coils for cast coil transformers completely impregnates and insulates the conductors with a polyester or epoxy resin system. The cast coil design allows for higher short circuit strength and overload capacity.
Due to significantly different coil designs, cast coil units require various insulating components than other types of dry type transformers. Standard cast coil insulation components supplied by The Gund Company include saturated DMD, NMN/GMG, glass epoxy B-stage layer insulations, and “dogbone” spacer sticks.
- Standoff Insulators
- Bus Support Angles & Channels
- Layer “Turn” Insulation
- Layer Insulation Tape
- “Dogbones” – Axial Spacer Sticks
- Coil Support Blocks
- Lead Supports, Spacers, & Clamps
- Lead Insulation – Sleeving
- Fasteners – Rods & Nuts
ELECTRONIC TRANSFORMERS
Using the term “electronic transformers,” we intend to capture a wide range of low-voltage transformers commonly used in electronic equipment applications. These units are typically rated at less than 600 volts.
They are used in various applications, from current transformers to instrument transformers, to lighting ballasts. Other specialty magnetics also fall into this category, such as shunts and chokes. The range of electronic transformer types and applications is nearly unlimited.
- Fabricated Winding Bobbins
- Core Insulation
- Layer Insulation
- Layer Insulation Tape
- Lead Insulation – Sleeving
- Terminal Boards
- Fuse Boards
REACTORS
Reactors have either iron core or air core construction. They help control quality by limiting load faults and surges or high-power lines.
In building substations near loads that could result in severe swings in power quality, reactors are employed. Reactors are often used in conjunction with capacitor banks to help control power quality. All air-core reactors have conducting windings that are wound much like a disc-wound, dry type transformer coil.
| Common Rigid Insulation Materials in Dry Type Transformers | ||
|---|---|---|
 Rigid Insulation | ||
| GPO-3, UPGM 203 | GPO-1 (N155) | |
| GPO-1 (N180) | GPO-1 (N220) | |
| Convolute Wound Tubing | Filament Wound Tubing | |
| SG-200 & HST-II | NEMA GPO-1, UPGM 201 | |
| NEMA G-12 EPGC 308 | NEMA G-10, EPGC 201 | |
| NEMA G-11, EPGC 203 | SG-200 & HST-II | |
| Standoff Insulators | Threaded Rods & Nuts | |
| UPGM 205, U205 | ||
| Common Flexible Insulation Materials in Dry Type Transformers | ||
|---|---|---|
 Flexible Insulation | Nomex® Aramid Paper | G-Flex YT510 Aramid Paper |
| 3M Cequin® | 3M Tufquin® | |
| 3M Thermavolt® | Kapton® Polyimide Film | |
| DMD | PET Polyester Film | |
| NMN/GMG/APA | Click here to view additional material datasheets. | |
The Gund Company also offers a wide variety of Transformer Gaskets & Sealing Products for your upcoming project.
The Gund Company uses a “Dry Type Transformer Checklist” to help customers review materials,s, the process the process and component specifications. The checklist is also helpful for setting up kitting programs and vendor-managed inventory programs by transformer design.
Contact our knowledgeable transformer material specialists today to learn more.
G-Flex™ is The Gund Company’s brand of flexible insulation products. G-Flex™ product line includes aramid paper, flexible laminates, wire sleeving, felts, cordage and surge ropes, and insulating tapes.
The G-Flex™ is used in a variety of electrical applications. Some specific examples are transformer coil layer insulation, motor slot insulation, lead wire protection, insulation barriers, and numerous other applications.
G-Flex™ Markets
- Transformers
- Motors
- Generators
LIQUID FILLED POWER TRANSFORMERS
Large units that are liquid cooled and commonly classified by their rated power as: small, medium and large power transformers.
Small power transformer typically starts around 10 MVA with a maximum service voltage of 145 kV. Medium power transformers range from about 30 MVA to about 100 MVA and commonly work as network and generator step-up transformers. Large power transformer usually starts at ratings greater than 100 MVA and voltages greater than 345 kV. The Gund Company supplies a wide variety of insulation components for the full range of power transformer designs and ratings.
- Core Insulation Kits
- Step Blocks
- Core Blocks
- Fletch Plates
- Core Filler Rods
- Lead & Cleat Structure
- Support & Yoke Beams Insulation
- Fasteners (Rods & Nuts)
- Winding Forms
- Dovetail Strips
- Key Spacers
- Camping Rings
- Coil Support Blocks
- Washer Assembly
- Tap Changer Boards
- Tap Changer, Filament-Wound Housings
- Composite Core Cooling Ducts & Spacers
- Lead Clamps
- Lead Conduit Tubes
- Tap Changer Enclosure Gaskets
- Bushing Gaskets & O-Rings
- Radiator Gaskets
- Hand-hole and Man-hole Gaskets
Ranprex® Densified Laminated Wood
Manufactured in Italy by Rancan, distributed and fabricated in North America by The Gund Company.
For more information on our laminated densified wood material for the Electrical Oil Immersed Power & Distribution Transformer, please click here.
| Common Rigid Insulation Materials in Power Transformers | ||
|---|---|---|
 Rigid Insulation | ||
| G-11, EPGC 203 | NEMA G-10, EPGC 201 | |
| Nomex® Pressboard 994 | GPO-1 (N220) | |
| Pressboard | Paper Phenolic | |
| U205, UPGM 205 | Ranprex® Laminated Wood | |
| X, XX, XXX, PFCP 201, 202, 204 | G-Flex Aramid Pressboard | |
| G12 EPGC 308 | ||
| Common Flexible Insulation Materials in Power Transformers | ||
|---|---|---|
 Flexible Insulation | Kraft Paper | Crepe Paper |
| Nomex® Aramid Paper | G-Flex YT510 Aramid Paper | |
| Vulcanized Fiber (Fish Paper) | Click here to view additonal material datasheets | |
| Common Elastomeric Materials in Power Transformers | ||
|---|---|---|
 Gasket & O-Ring Materials | ||
| Buna-N | Cork | |
| Cork-Nitrile | Cork-Rubber | |
| Fluorocarbon | Fluorosilicone | |
| Nitrile | Sponge | |
| Viton | and more… | |
| Click here to learn more about transformer gasket & sealing materials. | ||
LIQUID FILLED DISTRIBUTION TRANSFORMERS
The most common are pole-mounted or pad-mounted. Pole-mounted distribution transformers are named so because they are mounted to utility poles in older urban or rural areas.
Most distribution lines are buried underground in suburban areas built within the last few decades, so transformers are erected on concrete pads in residential, commercial, or light industrial applications. The Gund Company manufactures and fabricates a variety of insulation material solutions for distribution transformers.
- Layer Insulation
- Layer Insulation Tape
- Core Step Blocks
- Coil Supports
- Hardboard Coil Packing & Shims
- Phase Barriers
- Ground Barriers
- Sight Window Barriers
- Lead Supports, Spacers & Clamps
- Fuse Boards
- Fuse Tubes
- Tap Changer Boards
- Enclosure Gaskets
- Bushing Gaskets
- O-Rings
| Common Rigid Insulation Materials in Distribution Transformers | ||
|---|---|---|
| Rigid Insulation | ||
| Angles & Channels | Filament Wound Tubes | |
| G10, EPGC 201 | G11, EPGC 203 | |
| GPO-1, UPGM 201 | GPO-3, UPGM 203 | |
| Low Power Factor – HP1 | Pressboard | |
| Ranprex® Laminated Wood | S2S Hardboard | |
| G-Board YT592, 593, 594 Aramid Pressboard (High Temperature) | G12 EPGC 308 | |
| Common Flexible Insulation Materials in Distribution Transformers | ||
|---|---|---|
| Flexible Insulation | Kraft Paper | Diamon-Coated Kraft Paper |
| LFT Paper | Crepe Paper | |
| Duct Paper – Stick Paper | Vulcanized Fiber (Fish Paper) | |
| YT510 Aramid Paper (High Temperature) | Click here to view additional material datasheets. | |
| Common Elastomeric Materials in Distribution Transformers | ||
|---|---|---|
| Gasket & O-Ring Materials | ||
| Buna-N | Nitrile | |
| Fluorosilicone | Cork | |
| Cork-Nitrile | Cork-Rubber | |
| Nitrile | Sponge | |
| Click here to learn more about transformer gasket & sealing materials. | ||
