At Prem Magnetics, we maintain an extensive inventory of in-stock coil bobbins and coil winding components in sizes to meet virtually any application. We routinely supply material for engineering projects, prototyping, and large or small coil production orders, plus many other coil winding and electronics applications.
Our large selection of in-stock material enables us to provide same day shipping of most coil bobbins and meet just-in-time manufacturing schedules. In addition, we provide custom transformer, inductor, and coil winding services to meet specific requirements.
Prem Magnetics expanded its bobbin inventory through the acquisition of Formco assets. Read the press release.
| Bobbins Parts Catalog | |||
|---|---|---|---|
| EE 28-29 | EI 094 | EI 187 | EE 24-25 |
| EE 26-27 | EI 375 | EI 21 | EI 625 |
| EI 75 | EI 87 | EI 100 | EI 112 |
| EI 125 | EI 137 | EI 150 | EI 175 |
| UI | Pot Cores | Round | |
About Our Coil Bobbins and Coil Formers
Coil bobbins, also referred to as coil formers, are the winding platform at the heart of every transformer and inductor build. Wire is wound directly onto the bobbin to form the coil, which is then assembled with the corresponding core to complete the magnetic circuit. The terms coil bobbin and coil former are used interchangeably across the industry; both refer to the same component.
Prem Magnetics stocks transformer bobbins, inductor bobbins, and magnetic bobbins across five core styles: EE, EI, UI, Pot Core, and Round. All current inventory consists of through-hole bobbins. Surface mount styles are available on request through our supplier network, please contact us to discuss your requirements.
Bobbin Materials and UL 1446 Compliance
Bobbin material selection directly affects the temperature performance of the finished transformer or inductor. UL 1446 governs the insulation systems used in completed transformer designs, and the temperature rating of the bobbin material contributes to the overall UL 1446 compliance of the finished unit. Prem Magnetics stocks coil bobbins in materials suited to a range of temperature and application requirements:
- Glass Filled Nylon: Our standard stock material. A durable, widely-used thermoplastic that is well suited to most standard transformer and inductor applications.
- Nylon 6/6: Available in selected sizes for applications where glass fill is not required.
- Rynite: Carries the highest temperature rating of the three materials and is available on request for demanding applications.
If you are unsure which material is right for your application, our team can advise on the appropriate coil winding bobbins to meet your temperature and compliance requirements.
Bobbin Styles and Core Compatibility
Each bobbin style is designed to pair with a specific core geometry. Selecting the correct transformer bobbin or inductor bobbin for your core type ensures proper fit, reliable winding, and predictable electrical performance. Our current range covers the following styles:
- EI Bobbins: The most widely used style for power transformers and chokes. Available in standard sizes from EI 094 through EI 625. Download individual spec sheets from the parts catalog above.
- EE Bobbins: Used in switching transformer and switchmode power supply applications. Available in EE 24-25, EE 26-27, and EE 28-29 sizes.
- UI Bobbins: For use with UI core configurations in power transformer and choke applications.
- Pot Core Bobbins: Suited to high-frequency and RF applications where core shielding is important.
- Round Bobbins: For use with cylindrical core configurations.
Wire bobbins are available in the sizes listed above. If you require a size or style not shown, contact us, we can source additional styles through our supplier network or produce custom bobbins to your specification.
Custom Coil Winding Services
If your project calls for more than standard components, Prem Magnetics offers complete custom transformer, inductor, and coil winding services. We can wind to your specification using the bobbins and cores in our inventory, or source materials to meet unique design requirements.
We also offer 3D printing services for custom production-grade bobbins made to order, an ideal option for applications where standard sizes do not apply. Contact us or visit our Custom Services pages to learn more.