As we all know, the most feared thing for any electrically charged equipment or machine is leakage and short circuit.

Today we will discuss the current status of the application of major insulating materials in drive motors for new energy vehicles.

Insulation system
Typical insulation solutions for current-driven motors can generally be categorized into primary and secondary insulation.
Primary insulation is critical to the safe operation of the motor and includes electromagnetic cable insulation, slot insulation, phase insulation, slot wedge insulation, impregnating varnish, and so on.




Secondary insulation acts primarily as a secondary insulation to provide mechanical support and protection for the coil and includes insulation sleeves, bonding wires, busbar insulation and weld joint coatings.

Corona Resistant Enameled Wire
Drive motors are rotating faster and faster, and the power density of electric drive systems is increasing. The performance and quality requirements for enameled wires will become more and more stringent.

Currently, nanoparticle-modified H-class (or higher) corona-resistant enameled wires are mainly used in electric vehicle drive motors.

The enamel film of this kind of enameled wire is developed from the first three layers to the last two layers. Due to the short service life of the three-layer coating and the relatively poor adhesion of the enamel film, it gradually fails to meet the requirements.

In 2000, DuPont developed a two-layer corona resistant enameled wire. The bottom coating is a nanoparticle-modified polyesterimide corona-resistant coating, and the top coating is a PAI coating.

Since its introduction, the secondary coating has been widely used in the field of drive motors. In recent years, with the rise of oil-cooled engines, single-layer corona-resistant PAI enameled wires have been increasingly used due to their resistance to ATF oil and high temperature.

Corona Resistant Enameled Flat Copper Wire
As we all know, the materials and technologies used are constantly changing depending on the technology of the subject of application. No material is foolproof.

With the rapid development of flat wire technology, higher slot filling ratio and power density make more and more host factories choose flat wire motors.
However, the four "R" corners of corona-resistant enameled flat wire are poorly coated. In current applications, weaknesses such as corona resistance degradation and unstable performance are frequently observed.

In addition, some recent commercial applications use PEEK extruded onto the enameled wire instead of solvent-based dip coating.

Insulation Dip Resins
Vacuum impregnation (VI) resins and vacuum pressure impregnation (VPI) resins are the main insulating treatments for motor stators. Generally, the base resin is a high-strength, heat-resistant modified polyester or polyesterimide.

It is worth mentioning that nanoparticle modification technology can improve paint efficiency, heat resistance and corona resistance by adding nano-organic particles.

Speaking of the status quo, in recent years, resins adapted to new processes such as coil heating curing, ultraviolet curing, and rotary drop injection have also entered the picture.

Among them, the electric heating process is an efficient new method. It takes only a few minutes from impregnation to resin gel, and the whole process can be completed in about an hour. In addition, the amount of coating can be precisely controlled, filling performance is good, and no resin curing residue is produced.

However, the main equipment of the electric heating process is still controlled by foreign companies such as Germany and Italy, and the import price is high. There is no large-scale internal expansion yet.

Soft composite material
At present, non-oil-cooled drive motor slot insulation, slot wedge and interface insulation is mainly used two layers of polyaramide fiber paper (such as Nomex) and a layer of PI film composed of soft composite materials.

This insulation material heat-resistant class H, and more economical, so it is widely used. However, they are slightly less resistant to corona and ATF oil.

With the popularity of oil-cooled engines, these soft, oil-intolerant materials began to fail and were prone to delamination, which degraded insulation performance.

This creates a "vicious circle": in order to improve oil resistance, a single layer of thicker polyarylamide fiber paper with better oil resistance is used in engine development and design;

However, the electrical properties of this material are poor. In order to improve the insulation properties, the design thickness of the material should be increased. The increase in thickness will inevitably affect the power density, thus increasing the manufacturing cost of the whole engine.