What Is Hair-PIN Motor Flat Wire?
Hair-PIN Motor Flat Wire is a rectangular (flat) enameled copper wire specifically designed for hairpin winding technology in electric motors. Instead of using traditional round magnet wire wound continuously around the stator, hairpin motors use precisely formed U-shaped ("hairpin") flat conductors that are inserted into the stator slots, twisted, and laser welded together to form the winding.
This technology has become the preferred solution for electric vehicles (EVs),hybrid vehicles (HEVs),industrial servo motors,and high-efficiency traction motors because it enables higher power density, improved efficiency, and better automated manufacturing.
What Is a Hairpin Winding?
A hairpin winding consists of rigid, rectangular copper conductors bent into U-shaped pins.
The manufacturing process typically follows these steps:
Produce insulated rectangular magnet wire.
Cut the wire to an exact length.
Bend it into a U-shape (hairpin).
Insert the hairpins into the stator slots.
Twist the wire ends.
Laser weld the joints.
Apply insulation and resin impregnation.
Compared with traditional random-wound round wire, this process is highly automated and suitable for large-scale EV motor production.
Common Insulation Systems
Hairpin flat wire commonly uses high-temperature enamel coatings such as:
Polyesterimide (PEI)
Polyamideimide (PAI)
Dual-Coat PEI + PAI
Class 180
Class 200
Class 220
These insulation systems provide excellent resistance to:
High temperatures
Partial discharge
Automatic transmission fluid (ATF)
Refrigerants
Transformer oil
Coolants
Mechanical abrasion