Superior performance for the world’s most demanding electrical applications
The Nomex® family of products provides superior performance in transformers, motors, generators and many other types of electrical equipment. Every Nomex® product—from papers, pressboards and non-wovens to fabricated parts and more specialized forms like laminates and crepe papers—offers high levels of electrical, chemical and mechanical integrity. With performance that has stood the test through nearly 50 years of continuous use, the Nomex® family offers a dependable answer to your unique material needs.
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Making wind power a viable energy source
In collaboration with CG Power and Areva Wind, DuPont helped ensure the reliability of wind turbines placed in harsh North Sea conditions near Bremerhaven, Germany. At the CG Power factory, Xavier Fanichet explains how the wind turbines use transformers constructed with DuPont™ Nomex®, providing increased durability and reliability to turbines that will spend the next few years out on the high seas.
Introduction to Nomex® for Electrical Insulation
Nomex® for Dry-Type Transformers
Nomex® offers proven performance in dry-type transformers. Ventilated dry-type transformers (VDT) and cast resin transformers are growing in popularity worldwide. Nomex® papers and pressboards enable major design improvements in these types of transformers. For example, transformers insulated with Nomex® offer the following advantages to end users:
Safety
There are no fluids to spill, explode or burn, and Nomex® does not support combustion in air. In the case of a building fire, Nomex® products do not produce significant amounts of toxic smoke or dangerous particles. For this reason, among others, Nomex® is used extensively in honeycomb structures for aircraft interiors.
Low transmission losses
Since dry-type transformers insulated with Nomex® can be located close to their loads—inside factories, schools, hospitals and apartments—low-voltage lines can be shortened with a consequent reduction of the related losses.
Opportunities for reduced cost, size and weight
Dry-type transformers insulated with Nomex® can be designed with temperature rise up to 150K, requiring less conductor and core steel, and resulting in lower initial cost. This reduced size and weight contributes to ease of installation, especially since no vaults or catch basins are required. Smaller cores also mean lower no-load losses.
Harmonic loading capability
Transformers supplying loads with heavy harmonic content frequently see high hot spot temperatures. Standard transformers typically reduce the increase in base temperature to compensate, which increases the size of the unit. Dry-type and fluid-filled transformers designed with Nomex® still have a large reserve temperature capability to accommodate these hot spots.
Reserve capacity
If transformers are to be operated continuously at or near their rated loads, efficiency is of prime importance. In this case, one could select 80K rise VDT units insulated with Nomex®, allowing these units to operate continuously at 133 percent of rated load.
Proven reliability
Surveys published by IEEE show failure rates of modern, open ventilated, dry-type transformers equivalent to conventional liquid-immersed units in the same power and voltage classes. Repair time for dry-type units is also considerably shorter.
Resistance to humidity
Because the properties of densified Nomex® papers and pressboards are insensitive to moisture, transformers insulated with Nomex® perform satisfactorily in humid environments. This allows the placement of VDT or cast coil units in many locations not considered in the past.
Nomex® for Motors and Generators
Nomex® papers and pressboards have numerous applications in motors, generators and transformers. Nomex® is used in all types of rotating equipment, from AC and DC to random and form wound, and in sizes from miniature servo motors to 13.6 kV industrial drives and 150 MW steam-turbine generators. Additionally, Nomex® papers and pressboards provide significant advantages to users of motors and generators.
Thermal protection
When used as ground insulation, Nomex® improves reliability and can help prevent premature motor failure and equipment downtime. Nomex® does not shrink, become brittle, soften or melt during short-term exposure to temperatures as high as 300°C, and maintains good insulating properties continuously at 220°C for 10 years.
Motors may encounter temperatures considerably above their design ratings due to:
• Overloads caused by reduced speeds or stalled rotors
• Restricted cooling (especially in dirty environments)
• Reduced line voltage or unbalanced phases
• Frequent starts and stops
• Unusually high ambient temperatures
Because of its superior thermal properties and mechanical strength, Nomex® can help enhance motor performance and reliability.
Improved mechanical toughness
The strength and resilience of Nomex® papers and pressboards help extend rotating equipment life in severe operating conditions. These conditions include the severe shock and vibration seen in steel mill drives and railway traction motors, as well as the abrasion caused by thermal expansion and centrifugal forces in standby gas-turbine generators.
Versatility
Nomex® provides solutions for a broad spectrum of application needs and requirements, from servo motors to turbine generators and a vast array of thermal, electrical and mechanical demands.
Thicker grades of Nomex® papers are especially useful as slot liners, wedges, topsticks and midsticks. Additionally, Nomex® pressboards can be cut and shaped into sticks and more complex shapes. The high thermal resistance, high dielectric strength, cut-through resistance and tear strength of Nomex® papers may enable replacement of thicker materials, thereby gaining additional space in the slot.
NOMEX® EXCELS IN A VARIETY OF ELECTRICAL APPLICATIONS.
Nomex® UL-Recognized Insulation Systems
Introduction
More than 40 years ago, DuPont became the first electrical insulation manufacturer to obtain UL Recognition for our customers’ systems. Since then, we’ve developed hundreds of UL-Recognized systems, most of which use Nomex® paper as their primary insulation. UL-Recognized systems made with Nomex® have earned a reputation for safe, reliable operation.
Our systems can help save manufacturers much of the time and substantial testing costs needed to obtain UL Recognition, and we do not charge clients a fee to use them. In addition to the systems we offer based on our tests, many modifications to DuPont systems have been UL-Recognized by other material suppliers, offering users a wide variety of choices of UL systems made with Nomex®.
Component Recognition
Nomex® brand paper Types 356, 410, 411, 414, 818, plus pressboard types 992PSB, 993PSB, and 994PSB, are UL Component-Recognized (UL File E-34739) with an assigned Thermal Index (TI) of 220°C for both mechanical and electrical properties.
Insulation System Recognition
UL Standard 1446 prescribes procedures to determine the Relative Thermal Index (RTI) for an insulation system. A motorette is used to test all system insulation parts together. The models are tested through repeated cycles of high-temperature oven aging followed by environmental testing, including exposure to vibration, cold shock and high humidity.
Major Insulation: Ground and Interwinding Insulation
Ground and interwinding insulation are essential to the safe operation of a given unit because their failure, even if not noticeably affecting operation, could create a shock or fire hazard. Consequently, they are called “major” insulation. The superior thermal, electrical and mechanical properties of Nomex®, plus its outstanding flame resistance, make it a material of choice for these critical uses.
The amount of Nomex® brand paper required as ground or interwinding insulation in a motor or transformer is based on the thickness of paper used in the original motorette test. Today, many UL systems have been developed that allow the use of thinner ground materials.
Major Insulation: Magnet Wire—Wrapped Conductor Insulation
This is also major insulation and must be fully tested. Any type of DuPont™ Nomex® listed as major insulation is suitable for most insulation systems.
Substitution of Other Types of Nomex® Paper for Type 410 as Major Insulation
Because of the versatility of the Type 410 paper, in many systems it is the only material used. However, DuPont has developed alternative materials in response to customer requests.
UL allows substitution of other types of Nomex® brand paper for Type 410 based on extensive testing and follow-up examination with UL as a recognized plastic component. This substitution is based on a ratio of the thickness of the substitution product and Type 410, as follows:
Substitution of Other Materials for DuPont™ Nomex® Brand Paper
Per UL 1446, there is no “generic” substitution of aramid papers. The UL insulation systems are made specifically with DuPont™ Nomex® paper, not other manufacturers’ products. Only DuPont makes Nomex®.
Design Voltage Stress
DuPont suggests that continuous voltage stresses not exceed 40 V/mil (1.6 kV/mm) rms for most equipment, or less if the input or output power waveforms may be distorted by harmonics.
OUR SYSTEMS CAN HELP SAVE MANUFACTURERS MUCH OF THE TIME AND SUBSTANTIAL TESTING COSTS NEEDED TO OBTAIN UL RECOGNITION.
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Tell us a little more about yourself and we’ll send you information that’s tailored to your needs.