How EV Motor Manufacturers Choose Composite Insulation Materials

Discover how EV motor makers select composite insulation for 800V & oil-cooled systems. Xujue Electrical supplies custom NMN & NHN insulation solutions.

How EV Motor Manufacturers Select Composite Insulation Materials

Drive motors for new energy vehicles (EVs/HEVs)—especially high-speed, 800V SiC high-voltage platforms, and oil-cooled Hairpin motors—require composite insulation materials (insulation paper and insulation systems) with standards far exceeding those of traditional industrial motors.

When selecting materials, manufacturers cannot rely solely on a single temperature rating. Instead, they must conduct a systematic evaluation across four key dimensions: thermal performance, electrical performance, chemical compatibility, and mechanical processing.

EV motor slot insulation

I. Core Selection & Evaluation Metrics

1.Thermal Resistance & Thermal Aging Class (Class H / Class C)

Requirements: During rapid acceleration or heavy overload, local temperatures inside the stator slots often approach 180°C or higher.

Metrics: Priority must be given to composite structures featuring aramid paper (such as DuPont Nomex®) as outer layers and modified high-temperature-resistant film as the core layer. This ensures long-term operation under Class H (180°C) or Class C (200°C+) conditions without thermal embrittlement, delamination, or insulation failure.

2.High-Frequency Corona Resistance & High Breakdown Voltage (PDIV Metrics)

Requirements: Under 800V Silicon Carbide (SiC) high-voltage platforms, high-frequency switching of the inverter (high du/dt) easily triggers partial discharge.

Metrics: The Partial Discharge Inception Voltage (PDIV) of the insulation material must be 1.5 to 2.0 times higher than the system’s peak operating voltage. Standard PET films (such as low-end DMD) are quickly broken down by corona; thus, modified corona-resistant polyimide (PI) film composite materials are mandatory.

3.Hot ATF (Automatic Transmission Oil) Compatibility

Requirements: Modern high-performance motors widely adopt direct oil-cooling technology, where hot ATF oil is sprayed directly onto the end windings.

Metrics: The composite insulation paper and its laminating adhesive must withstand immersion in hot ATF oil at 150°C for over 1,000 hours, maintaining zero swelling, zero delamination, and no chemical degradation, with tensile strength retention exceeding 80%.

4.Mechanical Formability & Puncture Resistance (for Hairpin Winding Process)

Requirements: Hairpin motors have extremely high slot fill factors. The insulation paper needs to be folded into complex “S” or “B” shapes and withstand heavy mechanical insertion of copper conductors.

Metrics: The thickness must be precisely controlled between 0.15 mm and 0.30 mm. The material requires a smooth surface, high tear resistance, low fold springback, and zero micro-cracking at sharp bend corners.

NHN&NMN Composite insulation materials

II. Typical Application Scenarios & Material Combinations

III. Customized Solutions from Xujue Electrical

As a professional manufacturer of motor composite insulation materials, Xujue Electrical specializes in delivering high-performance NMN and NHN composite insulation materials. We offer tailored, custom solutions based on your specific motor applications and operating environments to ensure optimal electrical insulation, thermal endurance, and mechanical reliability for your drive systems.