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Custom Toroidal Transformer Cores
Bridgeport Magnetics manufactures custom toroidal transformer cores in Shelton, Connecticut. We wind, heat-treat, and precision-finish toroidal cores in-house, delivering tight tolerances, low core losses, and minimal EMI for high-volume OEM projects in precision metering, compact power density, medical isolation, and grid-edge applications. Fast custom quotes and samples available.
Four Decades of Toroidal Transformer Core Manufacturing
Years designing and manufacturing
toroidal transformer cores
O-core, C-core, E-core , Stepped Cores, Square Core, Fully Custom Capabilities
Maximum OD, with capabilities up to 1000mm ID
Manufactured weight up to 800kg
Precision Custom Toroidal Transformer Cores
Bridgeport Magnetics manufactures custom GOSS toroidal cores and O-cores at our vertically integrated facility in Shelton, Connecticut. We handle every step in-house – core winding, heat treatment, and precision finishing – to deliver tight tolerances, low core losses, and consistent magnetic performance.
These closed magnetic path cores offer superior flux containment, minimal EMI, and higher efficiency than traditional laminated designs. They are built for high-volume OEM projects in precision metering, compact power-density applications, medical isolation, and grid-edge systems.
Custom Toroidal Core Offering
Toroidal standard and custom cores offering a continuous wound design with excellent magnetic efficiency, low core losses, minimal electromagnetic interference, and compact size for high-performance transformers and inductors.
Precision cold-rolled grain-oriented silicon steel C-cores that provide superior magnetic performance and easier assembly compared to traditional laminated cores for 50/60 Hz transformers and inductors.
Grain-oriented silicon steel E-cores offering a traditional laminated core design with reliable magnetic performance and easy assembly using pre-wound coils for power transformers and inductors.
Grain-oriented silicon steel toroidal cores with a circular cross-section, delivering higher power density and a lower profile than standard toroids for compact transformer designs.
Secure mounting kits with center bolts, steel washers, and neoprene pads that provide vibration-resistant and electrically insulated installation for toroidal transformers and inductors.
Ultra-low loss amorphous alloy C-cores engineered for high-efficiency switch-mode power supplies, inverters, and renewable energy systems where minimal core losses and reduced size are essential.
Custom Toroidal Core Capabilities
| Feature | Capability | Materials | Size / Performance Range |
|---|---|---|---|
| Core Types | Fully custom toroidal cores, O-Cores, C-Cores | GOSS, Nanocrystalline, Amorphous | Custom OD, ID & height |
| Primary Material | Grain-Oriented Silicon Steel (GOSS ) | GOSS | Up to 700 mm OD |
| Advanced Materials | Nanocrystalline and Amorphous cores | Iron-based | Large custom sizes available |
| Special Constructions | Stepped cores, custom cross-sections, very large cores | GOSS, Nanocrystalline, Amorphous | Up to 1400 mm OD |
| Core Weight | From small precision cores to very large | All materials | Up to 800+ kg |
| Manufacturing Processes | Core winding, annealing (heat treatment), vacuum impregnation | All materials | Custom |
| Finishing Options | Bare, Epoxy coating, Fluidized bed epoxy, Impregnated fluids, Polycarbonate encapsulation | All materials | Custom |
| Dimensional Tolerances | High Precision custom tolerances | All materials | Engineered to specification |
Through our custom toroidal cores and O-core designs, we deliver the precision performance, low core losses, and scalable reliability that tomorrow’s high-density AI data centers, precision metering systems, and grid-edge infrastructure demand.
Precision Current (Metering) Transformer Cores
Custom toroidal cores for revenue metering, smart grid, and high-accuracy instrumentation. Nanocrystalline and GOSS cores deliver the low phase error and tight tolerances required for Class 0.1 and 0.2S current transformers.
Compact High Power Density Designs
O-core toroidal cores are ideal for space-constrained applications such as rack-mounted power supplies, data center equipment, and industrial systems that require higher power in a lower profile.
Medical Isolation Transformers
Custom toroidal cores used in medical-grade isolation transformers and equipment where low leakage current and minimal EMI are critical.
Grid Edge & Renewable Energy Systems
Toroidal cores for inverters, power quality equipment, energy storage, and dynamic grid-edge devices that demand high efficiency and low losses.
Industrial Power & Control Equipment
Custom toroidal cores for UPS systems, motor drives, and industrial power transformers where consistent quality and reliable supply at volume are essential.
Vertically Integrated facility in Shelton, CT
Core winding
using precision winding equipment for consistent build quality
Annealing (heat treatment)
to optimize magnetic properties and minimize core losses
Vacuum impregnation
for mechanical stability and insulation performance
Precision finishing
including epoxy coating, fluidized bed epoxy, and polycarbonate encapsulation
Reliable toroidal cores, manufactured to spec.
Custom GOSS, nanocrystalline, and amorphous toroidal cores, O-cores, C-cores, E-cores, stepped cores, and components – built to your exact specifications in Shelton, Connecticut.
Frequently Asked Questions
What types of custom toroidal cores do you offer?
We manufacture fully custom toroidal cores, O-cores, C-cores, E-cores, stepped cores, and related components. All cores are built to your exact specifications, including large and complex designs.
What materials are available for custom toroidal cores?
We offer Grain-Oriented Silicon Steel (GOSS), nanocrystalline, and amorphous cores. GOSS cores are produced in-house, while nanocrystalline and amorphous options are available for applications requiring superior magnetic performance and low losses.
What is the maximum size of toroidal cores you can produce?
We can support very large custom toroidal cores up to 1400 mm outer diameter and over 800 kg, including stepped core designs. Both small precision cores and large high-power cores are within our capabilities.
Do you offer samples or prototype toroidal cores?
Yes. We support prototype and sample requests so you can evaluate fit, performance, and quality before moving into production. We typically respond to sample and quote requests within 24–48 hours.
Where are your toroidal cores manufactured?
GOSS toroidal cores and O-cores are precision-manufactured in our vertically integrated facility in Shelton, Connecticut. This gives us full control over quality, lead times, and consistency for high-volume OEM projects. For specialized cores we work with our global supply network.
What is your typical lead time for custom toroidal cores?
Lead times vary depending on size, material, and quantity. Because we control core winding, annealing, and finishing in-house, we can often provide faster and more reliable lead times than companies that outsource core production. Contact us with your specifications for a current lead time estimate.
