When designing or selecting an insulated winding wire for use in a wound component, it is important to consider the following key factors:
- What is the range of operating temperatures that the product will see in your application?
- What temperatures will the wire be subjected to in downstream manufacturing processes?
- What is the expected/required thermal life for the end-product?
- What voltage rating is required for this application (including transient overvoltages)?
- What are the regulatory and testing requirements that I should be concerned with?
- Is basic, supplementary, or reinforced insulation required for this application?
- Is there a UL recognized insulation system out there with both this wire and the bobbins, core tubes, tapes, varnishes, etc. that I would like to use with it?
This article focuses on the first three questions related to temperature considerations. The other factors, while equally important, will be addressed in future articles.
Key Temperature Considerations
Operating Temperature Range
The insulation materials selected should have a temperature rating that is greater than or equal to the maximum operating temperature. Higher temperatures will accelerate aging and shorten the product’s lifespan.
Melting Temperature
Thermoplastic materials soften and can be made to flow again at elevated temperatures, so it is important to avoid temperatures near the melting point of thermoplastic materials when working with them. For reflow solder applications, processing temperatures with RoHS compliant solders are typically too hot for Class B and Class F insulation materials. In these cases, PFA is recommended as it holds up better in processing.
Expected Thermal Life
Insulated winding wires are rated for a minimum expected thermal life of 20,000 hours at their rated temperatures. If your desired or required operating life exceeds 20,000 hours, consider using an insulated winding wire with a higher temperature rating when designing wound components.
Note: For applications requiring an operating life of 5,000 hours or less, it may be possible to use an insulated winding wire with a temperature rating up to 20°C less than the maximum operating temperature. This is based on accelerated aging test data from UL Standard 1446 but may not apply to all applications. Always consult relevant Codes, Standards, and Authorities Having Jurisdiction (AHJ’s) to confirm acceptability.
Common Insulation Materials Comparison
Extruded Insulation Materials
| Material | Common Trade Name | Temperature Class | Maximum Operating Temperature | Melting Point |
|---|---|---|---|---|
| ETFE (Ethylene Tetrafluoroethylene) | Tefzel™ | F | 155°C | 220-280°C |
| FEP (Fluorinated Polyethylene) | Teflon™ | F | 155°C | 255-260°C |
| PFA (Perfluoroalkoxy) | Teflon™ | H | 180°C | Approx. 305°C |
Taped Insulation Materials
| Material | Common Trade Name | Temperature Class | Maximum Operating Temperature | Melting Point | Notes |
|---|---|---|---|---|---|
| PET (Polyethylene Teraphthalate) | Mylar | N/A* | N/A* | 200-260°C | Typically used under other tape layers |
| PPS (Polyphenylene Sulfide) | N/A | F | 155°C | Approx. 280°C | |
| PEN (Polyethylene Naphthalate) | N/A | H | 180°C | Approx. 270°C | |
| PI (Polyimide) | Kapton® | H | 180°C | N/A (Decomposes at 520°C) | Typically FEP-backed |
Trademarks:
- Tefzel™ and Teflon™ are trademarks of Chemours
- Kapton® is a trademark of DuPont Electronics, Inc.
Need help determining the right insulation materials for your application? Contact our knowledgeable sales and engineering teams at sales@rubadue.com or +1(970) 351-6100.