3 Common Types of Electrical Insulation Paper for Motors
Electrical insulation paper is a key component in motor insulation systems. It helps provide electrical separation, mechanical support, and thermal stability for windings during long-term operation.
Among commonly used laminated insulation materials for motors, DMD, NMN, and AMA are three widely adopted options. This article explains their typical structures, practical differences, and how to select the right insulation paper for motor applications.
DMD insulation paper is a laminated insulation material generally made from polyester film combined with polyester nonwoven fabric.
Key characteristics
Flexible and easy to process
Good electrical insulation performance
Cost-effective for general motor insulation systems
Typical motor applications
Slot insulation
Phase insulation
General-purpose motor winding insulation
DMD is commonly selected for motors with moderate thermal and mechanical requirements, where processing convenience and cost efficiency are priorities.
2) NMN Insulation Paper (Nomex®–Mylar–Nomex®)
NMN insulation paper is a three-layer laminate consisting of aramid paper / polyester (Mylar) film / aramid paper.
In many standard NMN specifications used in the motor industry, the “N” typically refers to DuPont™ Nomex® aramid paper, which is a branded aramid insulation paper often associated with higher material cost.
Key characteristics
Strong thermal endurance and stable insulation performance
High mechanical strength and tear resistance
Good long-term reliability under thermal aging
Typical motor applications
Higher-performance motors
Motors requiring improved thermal endurance and long service life
Applications with higher mechanical stress on insulation components
Practical note: NMN using branded aramid paper (e.g., Nomex®) is often chosen when customers require brand-specified materials or when procurement standards explicitly call for it.
3) AMA Insulation Paper (Aramid–Mylar–Aramid)
AMA insulation paper is also a laminated structure made of aramid paper / polyester (Mylar) film / aramid paper.
In practice, AMA may be supplied with aramid paper from different sources, including equivalent aramid insulation paper options that meet required electrical insulation performance and are often more cost-competitive than brand-specified materials.
Key characteristics
Mechanical reinforcement from aramid paper layers
Reliable dielectric insulation provided by polyester (Mylar) film
Commonly used for Class F (155 °C) motor insulation systems
Typical motor applications
Motor slot insulation
Phase-to-phase insulation
End-winding insulation
General selection guidelines
Choose DMD for standard motors with moderate requirements and strong cost sensitivity
Choose NMN when specifications require branded aramid paper (e.g., Nomex®) or higher assurance requirements
Choose AMA when you need Class F insulation performance with a focus on cost-efficiency, while still meeting the required electrical and mechanical criterial
Conclusion
DMD, NMN, and AMA are three common laminated insulation materials used in motor insulation systems. Understanding their structural differences and purchasing considerations helps ensure proper selection for performance, reliability, and cost.
For motors requiring reinforced insulation and stable Class F performance, AMA insulation paper is a widely used option.
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