NMN Insulation Material for High-Voltage Motors: Applications & Selection Guide

Application and Selection of NMN Insulation Material in High-Voltage Motors High-voltage motors (3kV, 6kV, 10kV, and...

Application and Selection of NMN Insulation Material in High-Voltage Motors

High-voltage motors (3kV, 6kV, 10kV, and above) have significantly higher insulation system requirements than low-voltage motors. NMN insulation material (Nomex + Polyester Film + Nomex) is widely used in stator slot insulation, interphase insulation, and end-winding insulation due to its excellent thermal resistance, mechanical strength, and electrical performance.

NMN insulation paper for motor

1. Structure and Properties of NMN Insulation

Structural Features

Outer layer: Nomex paper
Middle layer: Polyester film (PET)
Typical structure: N-PET-N

Key Performance Advantages

2. Major Applications of NMN in High-Voltage Motors

Stator Slot Insulation

High-voltage stator slots experience strong electric fields, requiring reliable insulation
PET film provides mechanical support, Nomex ensures thermal and dielectric strength
Recommended thickness: 0.25–0.35 mm

Interphase Insulation

Voltage difference between coils is high, requiring high dielectric strength
NMN is used for winding interleaving and phase separation
Recommended thickness: 0.18–0.25 mm

Turn-to-Turn / Layer Insulation

Prevents breakdown between winding layers
Flexible NMN fits tightly on windings, enhancing insulation safety
Recommended thickness: 0.15–0.18 mm

End-Winding Insulation

End regions have strong electric fields and higher temperatures, prone to partial discharge and thermal aging
NMN is used for end barriers, slot end insulation, and end winding padding
Recommended thickness: 0.2–0.3 mm

Auxiliary Insulation in Combination with Mica Tape

Main insulation in high-voltage motors typically uses mica tape
NMN serves as slot, interphase, and end-winding auxiliary insulation
Enhances mechanical durability, uniform electric field distribution, and slot stability

3. Selection Guidelines for NMN in High-Voltage Motors

Thickness Selection

Internal Structure Selection

Standard NMN (3–6kV motors): Nomex 50g + PET 50 μm + Nomex 50g
Enhanced NMN (≥10kV motors): PET 75–125 μm + Nomex 2×50g, delamination strength ≥1.2 N/10mm

Corona Resistance Requirement

For VFD-driven or high-frequency motors, select corona-resistant NMN
Corona-resistant NMN can last 3–8 times longer than standard NMN

Supplier and Certification Requirements

UL certification
Thickness, dielectric strength, and delamination testing
No delamination, cracks, or foreign particles on the surface

4. Comparison of NMN with Other Insulation Materials

5. Typical Applications in High-Voltage Motors

10kV large cooling water pump motors
Heavy-duty motors in mining and steel plants
VFD-driven high-voltage motors
Circulating pump motors in power plants
Coal mill high-voltage motors
High-voltage compressors and fans
Large centrifuge motors
Industrial high-voltage blower motors

6. Summary

NMN insulation material provides:
High dielectric strength
Excellent mechanical strength
F-class thermal resistance
Good long-term stability and flexibility
Cost-effective performance
It is widely used in slot insulation, interphase insulation, and end-winding insulation of high-voltage motors. For higher-grade requirements (H-class, corona-resistant, high-frequency), NHN or PI-based insulation can be considered.