Hairpin motor is a permanent magnet synchronous motor (PMSM) equipped with hairpin flat windings. It uses U-shaped flat copper wires to substitute traditional round enameled wires.

While it follows the fundamental electromagnetic principles of a standard PMSM, its main innovation lies in the stator winding construction: the conventional thin round copper wires are replaced with U-shaped flat copper “hairpins”.

Basic Working Principle of PMSM
The controller supplies three-phase alternating current to the stator windings, producing a rotating magnetic field. Permanent magnets are embedded on the rotor, and the rotor’s magnetic field rotates in sync with the stator’s rotating magnetic field.

The magnetic attraction between the two fields spins the motor shaft continuously and generates output torque.

Simply put: The supplied current creates a rotating magnetic field that drives the permanent magnet rotor to rotate synchronously.

Unique Structure & Advantages of Hairpin Winding (Compared with Conventional Round‑Wire Motors)
In traditional motors, many thin round enameled wires are wound into the slots of the stator core.

For hairpin motors, flat rectangular copper wires are bent into a U shape (resembling a hairpin) and inserted into the stator core slots. This design allows far more copper to be fitted within each slot, significantly boosting the slot fill rate.

The flat copper wires also maintain large-area contact with the stator core for rapid heat transfer.

When running, three-phase current flows through these U-shaped flat copper wires to form the rotating magnetic field.

The higher copper packing ratio enables the motor to handle larger current and produce greater torque and power in the same footprint.

In addition, the extensive contact between flat wires and the core improves heat dissipation, leading to lower temperature rise during long-duration high-power operation.