DMD Insulation Material vs PET Polyester Film for Electric Motor Insulation

Learn the differences between DMD insulation material and PET polyester film for electric motors. Explore their features, applications, benefits, and insulation solutions from X...

With the rapid development of new energy vehicles, industrial automation, high-efficiency motors, and intelligent equipment, the requirements for motor insulation systems are continuously increasing. Insulation materials must not only provide excellent electrical insulation performance but also meet the requirements of heat resistance, mechanical strength, flexibility, and long-term operational reliability.

In modern electric motor manufacturing, flexible insulation materials are widely used in critical areas such as stator slot insulation, turn insulation, layer insulation, and winding wrapping insulation. Among them, DMD composite insulation material (DMD Insulation Material) and PET polyester film (PET Polyester Film) are two of the most commonly used flexible insulation materials.

1. Introduction to DMD Composite Insulation Material

DMD is a flexible composite insulation material consisting of three layers:

Polyester Fiber Non-woven Fabric + Polyester Film + Polyester Fiber Non-woven Fabric

Also known as:

DMD Insulation Paper / DMD Composite Insulation Material

The structure includes:

D (Dacron): Polyester fiber non-woven fabric, providing excellent mechanical strength and good resin absorption performance;
M (Mylar): Polyester film (PET Film), providing outstanding dielectric insulation properties;
D (Dacron): Outer polyester fiber layer, improving abrasion resistance and processing performance.
Through its multi-layer composite structure, DMD combines the excellent electrical insulation properties of polyester film with the mechanical strength and flexibility of fiber materials, making it an important material in modern motor insulation systems.

2. Main Applications of DMD in Electric Motors

2.1 Stator Slot Insulation

Slot insulation is one of the most critical parts of a motor insulation system.

DMD insulation material is installed between:

Motor iron core slot and winding coils

Main functions include:

Preventing direct contact between enamel wire and the iron core;
Improving the motor’s dielectric strength;
Reducing the risk of partial discharge;
Enhancing the reliability and service life of the motor.

Due to its excellent flexibility, tear resistance, and processing performance, DMD is suitable for automatic slot insertion processes used in modern motor manufacturing.

2.2 Phase Insulation

In three-phase motors, reliable electrical isolation between different phases is essential.

DMD materials provide:

Stable electrical insulation protection;
Improved phase-to-phase voltage resistance;
Reduced risk of insulation breakdown during long-term operation.

2.3 End Winding Insulation

The end part of motor windings is exposed to:

Vibration;
Thermal cycling;
Mechanical stress.

DMD insulation materials provide excellent mechanical support and insulation protection for winding ends.

3. Introduction to PET Polyester Film

PET (Polyethylene Terephthalate) polyester film is a high-performance flexible insulation film.

In the electrical industry, it is also known as:

Polyester Insulation Film;
PET Electrical Insulation Film;
Mylar Insulation Film.

PET film offers excellent:

Electrical insulation performance;
Mechanical strength;
Dimensional stability;
Moisture resistance;
Flexibility.

Common thickness range:0.025mm – 0.35mm

4. Applications of PET Film in Electric Motors

4.1 Turn Insulation

In motor windings, reliable insulation between enamel wires is essential.

PET film can effectively:

Improve turn-to-turn voltage resistance;
Reduce the risk of short circuits;
Extend motor service life.

4.2 Layer Insulation

In multi-layer winding structures, PET film is used for:

Insulation between coil layers;
Preventing electrical breakdown;
Improving overall insulation performance.

4.3 Motor Lead Wire Insulation Protection

PET film can also be used for:

Motor connection wire protection;
Cable wrapping;
Electrical isolation applications.

5. Comparison Between DMD and PET Film

6. Development Trends of Motor Insulation Materials

With the development of electric motors toward:

Higher power density;
Higher rotational speed;
High-frequency operation;
Miniaturization;

traditional insulation systems are gradually upgrading toward higher-performance materials.

Future motor insulation systems will increasingly adopt advanced flexible insulation materials such as:

DMD (Class B/F)
NMN (Class F)
NHN (Class H)
Polyimide Film (PI Film, Class C)

to achieve higher temperature resistance, better electrical performance, and improved reliability.

7. Xujue Electrical Flexible Insulation Material Solutions

Xujue Electrical specializes in the research, development, and manufacturing of electrical insulation materials, providing high-performance insulation solutions for motors, transformers, new energy vehicles, and industrial electrical equipment.

Our product range includes:

DMD composite insulation materials;
NMN and NHN flexible composite insulation materials;
PET polyester insulation film;
Polyimide film (PI Film);
Customized motor slot insulation materials.

With advanced manufacturing technology and a comprehensive quality management system, Xujue Electrical is committed to providing reliable and efficient insulation material solutions for global motor manufacturers.