What is UL Certification and Why Does it Matter?
Increased energy demands, aging electrical systems, grid modernization and the push for greater energy efficiencies are challenging the current electrical infrastructure.
Modernization of transformers and electric motors is propelling the demand for electrical insulation tapes. Key electrical equipment design stresses and assembly criteria demonstrate a need for insulating pressure sensitive adhesive tapes, uniquely designed to meet thermal, dielectric, mechanical and chemical compatibility requirements. With a combination of backings and adhesives, our CHR® Products are UL recognized with thermal capabilities that range from class A (105°C) to class N (200°C).
For this article, we connected with Nirmal Patel, Product Manager, CHR Tapes at Saint-Gobain® Tape Solutions, to further explore the importance of UL listing in the electro-mechanical market and gain a better understanding of how UL class type impacts the product features, capabilities and most common applications.
In this article
First, tell us about the applicability of our products within the energy system, specifically as solutions for electrical insulation.
Yes, our products work behind the scenes in power distribution, generation and transmission. Mainly, serving as insulation media for transformers, motors and generators. Products can help separate parts from each other to prevent short circuits or electrical arcing. They can be used as a spacer between coil wire and the metal housing to separate metal to metal contact within transformers, rotors and stators and avoid electrical shocks or explosions to the power system.
Tell us about the importance of the UL listing.
Within the electromechanical market, the UL (Underwriter Laboratories) listing is one of the most recognized and respected certifications. UL recognitions are a requirement by OEMs who manufacture transformers, motors and generators. UL 1446 is the standard to define both guidelines and methodologies for evaluating the performance of electrical insulation materials as well as insulation systems. By knowing the UL class, we can also better understand the product interactions. We use a thermal class rating based on test results such as full thermal aging tests, high-voltage full thermal aging tests, and short-term thermal aging tests which can demonstrate thermal degradation over time. The thermal classification that is specified by the UL recognition shows us what the product life expectancy is at a certain temperature range and the typical expected life of equipment at a rated temperature is about 20,000 hours.
Tell us about the high performance electrical insulation tapes that are certified to classes that are defined by UL 1446.
We currently have two brands of electrical insulation tapes to meet the challenging requirements of the electromechanical market as well as other markets such as aerospace, oil and gas, electronics or industrial. These brands are the CHR and h-old® product brands and they comprise a comprehensive portfolio of products for both North American and European markets.
Could you elaborate on what the UL letter class ratings mean?
A thermal class rating is issued based on test results after which a UL certification report is issued. The bottom line comes down to temperature range. So, UL class N (200ᵒC) and UL class H (180ᵒC) fall into the high-temperature classification. This means they have outstanding temperature resistance, good dielectric strength, chemical resistance and conformability. Within this high temperature class, we have the following:
- Fluoropolymer Tapes such as PTFE and FEP, generally ideal for insulation of end-windings in high temperature motors and generators.
- Polyimide (PI) Tapes which feature DuPont Kapton® and value grades of PI in full thickness ranges. These tapes have silicone adhesive and offer good conformability. They are often utilized in insulation of end windings in high temperature motors and generators.
- Glass Cloth Tapes which have silicone adhesive, high tensile and high thermal resistance. They are ideal for higher temperature coil winding applications and are used to band layers of insulation together.
UL Class F (155ᵒC), B (130ᵒC) and A (105ᵒC) reflect medium temperature. Some common products within this category include:
- PET Film/Non-woven and Paper Laminated Tapes are puncture resistant, strong, and highly conformable, making them ideal for phase insulation and coil wrapping.
- PET Film Adhesive Tapes are available in various thicknesses and colors and have high tack properties for adhering to a wide range of substrates. They are flame-retardant, printable, and compatible with varnishes and resins. They are commonly used for interlayer insulation, insulating smaller dry type transformers or toroidal coils, and final binding.
- Acetate Cloth-backed Tapes have a thermosetting rubber adhesive that provides excellent initial tack and high conformability. They are perfect for wrapping bobbins and smaller transformers.
- Double-sided Adhesive Tapes have good initial adhesion and electrical properties, making them ideal for fixing insulating material during transformer manufacturing.
Why is choosing the right class of insulation important?
The right class of insulation is vital to understand. If a lower class of insulation than is required is utilized in an application, it can result in damage or failure of the equipment as a result of too much heat. If the class of insulation utilized is higher than required, the result is an unnecessary added weight on the equipment as well as an unnecessary extra cost.
Engineers at the electrical equipment OEMs are pressed to find products that meet both quality and on-time delivery as well as stringent safety standard requirements. Working with flexible suppliers is vital to support steady market growth, mitigate supply chain complexities and respond quickly to new opportunities.