How to select Motor insulation paper

Motor insulation paper plays a dual pivotal role in electric motors as both an electrical barrier and a mechanical bu...

Motor insulation paper plays a dual pivotal role in electric motors as both an electrical barrier and a mechanical buffer:

It provides rigorous dielectric isolation between energized coils and the core/housing (ground insulation), as well as between different phase windings (interphase insulation), completely preventing current leakage and short circuits. Concurrently, it withstands abrasive scraping from sharp slot edges during the winding insertion process and absorbs alternating electromagnetic vibrations during motor operation. Furthermore, serving as a resin-absorbent matrix integrated with insulating varnish, it effectively blocks the ingress of moisture and oil contaminants while facilitating thermal dissipation, serving as a critical foundational material that ensures the long-term safe and stable operation of the motor.

How to select Motor insulation paper

1.Match by Thermal Class

The material’s maximum continuous operating temperature must exceed the hottest spot inside the motor:
Class B (130°C): Standard for small to medium, everyday AC motors.
Class E (120°C): Legacy low-voltage AC/DC motors (rarely used in new designs).
Class F (155°C): The current mainstream industry standard for industrial motors.
Class H (180°C): High-performance, heavy-duty, or variable-frequency drive (VFD) motors.

2.Match Thickness by Power & Voltage

Insulation thickness is directly correlated with dielectric requirements, motor size, and structural constraints:
Power below 10 kW: Generally uses 0.17 mm thickness.
Power above 10 kW: Recommended 0.21 mm thickness.
Frame Size (Center Height) 80–112 mm: Recommended 0.25 mm thickness.
High Voltage (>1000V): Requires 0.30 to 0.50 mm or greater to handle electrical stress.
Rotor Slot Insulation: Must ≥0.15 mm to prevent physical tearing.

3.Compare Common Composite Materials

Modern motor design relies heavily on multi-layer composite laminates to combine the dielectric strengths of films with the physical toughness of fibers.

 4. Account for Stress and Environment

Frequent Start/Stop: Generates severe thermomechanical stress. Check test specifications like IEC 60034-18-41 or GB/T 17948.6 for dynamic endurance testing.
Aging Margin: For severe Class F or H duty cycles, add a 20% to 30% thickness buffer to combat long-term material degradation.
Edge & Phase Isolation: Anchor edges and cross-overs with high-temperature insulation tapes. Flame-retardant PET or PI (Kapton) tapes are standard choices.