DMD Insulation Material Applications in Motors, Transformers & Reactors

DMD insulation material (types 6630/6641) is a flexible three-layer composite insulation consisting of a polyester fi...

DMD insulation material (types 6630/6641) is a flexible three-layer composite insulation consisting of a polyester film (PET) core laminated on both sides with polyester nonwoven fabric. It combines the high dielectric strength of the film with the mechanical robustness and excellent impregnation absorbency of the nonwoven layers. Typically rated for thermal classes B (130°C) or F (155°C), DMD is widely used for slot, turn-to-turn, and layer insulation in motors, electrical equipment, and transformers.

1. Structural Characteristics and Reliability of DMD Insulation

The three-layer structure of DMD provides multi-dimensional reliability:

Polyester Film Core:
Offers excellent dielectric properties, effectively preventing current leakage. It maintains stable insulation performance under medium-temperature conditions, reducing the risk of electrical breakdown.

Nonwoven Outer Layers:
Provide high mechanical strength and flexibility, enabling resistance to vibration and tensile stress during equipment operation. This prevents cracking or delamination of the insulation layer.

Integrated Lamination Structure:
Through specialized bonding and impregnation processes, the three layers form a cohesive insulation system that enhances both electrical safety and structural integrity.

In humid environments, DMD exhibits excellent moisture resistance and anti-aging properties. It does not readily absorb moisture under short-term exposure, and long-term use slows oxidative degradation, thereby reducing the risk of insulation failure. Furthermore, its low thermal shrinkage ensures dimensional stability at operating temperatures, maintaining stable insulation performance and preventing gaps from forming due to thermal expansion and contraction.

2. Adaptability and Application Advantages

DMD insulation material offers strong adaptability in various applications:

Flexible Forms:
Available in rolls, sheets, or custom-shaped components, suitable for continuous winding insulation or precision-cut insulating parts.

Process Compatibility:
Smooth surface allows easy bonding with other insulation materials such as varnishes and insulation papers. It is also compatible with processes like hot pressing and die cutting, enabling efficient manufacturing without increasing complexity.

Wide Applicability:
While primarily used in medium-temperature applications, DMD can be tailored (by adjusting PET thickness and nonwoven density) to suit different power ratings of low- and medium-voltage equipment, reducing the need for specialized materials and lowering procurement costs.

These advantages make DMD a cost-effective and versatile insulation solution, suitable for both standardized and customized electrical equipment.

3. Key Application Scenarios in Electrical Equipment

Insulation in Low- and Medium-Voltage Motor Windings

In motors such as household appliances and small industrial machines, winding insulation must withstand thermal rise and mechanical vibration. DMD is used as:

Insulation tapes wrapped around conductors

Interlayer insulation sheets between winding layers

The PET film ensures reliable insulation, while the nonwoven layers absorb mechanical stress. Its thin and flexible nature minimizes space usage, supports tight winding configurations, and prevents cracking during bending, ensuring long-term motor reliability.

Insulation in Dry-Type Transformers

In dry-type distribution transformers, insulation is required between the core and windings, as well as between windings and structural components. DMD can be processed into:

Insulating barriers between core and windings

Outer wrapping insulation for windings

It meets dielectric performance requirements while providing sufficient mechanical support to prevent displacement of windings during operation, ensuring stable insulation performance.

Insulation Support in Reactors

Reactors generate electromagnetic forces during operation, which may cause slight displacement of windings. DMD is used as:

Insulating spacers between windings

It provides both electrical insulation and mechanical support. The elasticity of the nonwoven layers helps absorb electromagnetic forces, preventing deformation of windings. Its ease of processing also allows precise adaptation to irregular winding structures, maintaining overall system stability.

Conclusion

DMD insulation material, with its balanced electrical, mechanical, and thermal properties, has become a preferred insulation solution for motors, transformers, and reactors. Its versatility, cost-effectiveness, and reliability make it an essential material in modern electrical insulation systems.