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X-Pin Motor Performance and Process Feature

1. What is a Hairpin Motor?

Hairpin motor refer to motors with flat copper-clad wire windings. It is a common type of electric motor, which consists of a stator and rotor, usually using flat copper wires as winding conductors.



It is mainly used in high-power motors and generator sets in the industrial field because these occasions require high power and efficiency of the motor.

With the gradual rise of the new energy automobile industry, hairpin motor have also begun to be applied to the vehicle field. Many application functions on vehicles use hairpin motor, such as automotive generators, starters, EPS (electric power steering) motors, main drive motors, P2 (parallel hybrid) system motors, etc.


2. Differences in Performance Between Flat Wire and Round Wire Motors

Flat wire motors are currently the mainstream form of motor windings. Compared with round wires, flat wires are beneficial to improving the motor slot full rate.

The slot full rate of round wire motors is about 50%, and the slot full rate of flat wire motors can reach more than 70%.

The increase in slot fullness means that more copper wires can be filled in while the space remains unchanged, generating stronger magnetic field strength and increasing power density.



3. Types of Hairpin Motors

The winding forms of flat wire motors mainly include I-pin, Hair-pin, X-pin and S-winding.


I Pin

The I-Pin winding is shaped like an I, inserted directly, and then soldered on both sides.

There is no need for single-slot assembly, further reducing the space reserved for winding assembly.

The disadvantages are that the welding process is cumbersome and the end size is large.



Hair-pin twists are shaped like hairpins.

It is first formed, then inserted, then welded on one side.

It is the most widely used form of flat wire winding.



X-pin winding is mainly optimized at the welding end.


Compared with Hair-pin, the X-pin has a lower end height, which can further reduce the size of the motor, which is conducive to the layout of the vehicle's axial space, improves power density, and the manufacturing process simpler than wave winding. The production line investment is based on the current Hairpin production The investment in wire upgrading is relatively low, and the product performance and investment significantly exceed that of wave winding, which will soon become a new trend in hairpin motors.



The shape of the S-winding is S-shaped. After forming, there is no need to weld the two ends, and the end space size is smaller, the NVH performance is better, the torque pulsation is reduced, and the smoother operation and better performance cooling effect are achieved.


4. The difference between X-pin and Hair-pin processes

4.1 Wire forming

The difference between the wire forming process and traditional Hairpin forming is not significant, and it is important to focus on the forming accuracy because X-pin does not have a cutting flat process, and the consistency of the pin angle after forming is high. As the paint removal length is only about 5mm, mechanical paint removal will cause the cross-section to not fully fit, and welding will leak laser. Therefore, laser paint removal can only be used.



Disadvantages: X-pin has higher precision requirements than Hairpin, and the equipment requires high wire feeding precision, which is difficult to implement.

Advantages: Compared with Hairpin, X-pin saves more than 20mm of copper loss and can remove paint from both sides.


4.2 Twisting method

The biggest change point of the X-pin relative to the Hairpin's torsion head is the cancellation of the straight line segment, which makes it impossible to achieve the barrel twisting method. Moreover, due to the lack of trimming technology, the end is not a flat surface. How to achieve torsion and maintain consistency in the twisted section is the key to torsion. A new twisting process is needed to ensure the consistency of the cutting surface after twisting, and the control of twisting rebound requires extremely high equipment accuracy and algorithm compensation.


4.3 ​​​​​​​Welding method

Hair-pin and X-pin are soldered differently.


Hairpin uses hot melt welding, and a solder ball is formed at the end. The heat-affected area is large, generally around 8-10mm², the welding area is 110% of the cross-sectional area, and the pull-out force is generally around 800-1000N.


X-pin uses low-temperature welding. The solder ball is no longer formed at the end and needs to penetrate downward. The heat-affected area is required to be small. The welding area is 80% of the cross-sectional area. The pull-out force is generally about 600-800N.


4.4 ​​​​​​​Insulation treatment

Hairpin uses impregnation paint + coating process to ensure insulation performance and strength.


X-pin can also use the impregnation paint + coating process, but the welding area and pull-out force of X-pin are lower than that of Hair-pin, so it is recommended to use a higher-strength end potting process for insulation treatment. This process can improve the insulation performance and strength of the motor, and also improve the reliability of the motor.


Finally, X-pin motors have higher power density than Hair-pin motors, and the production process is relatively simple, which improves the efficiency of the motor.


At the same time, due to the reduction of production processes, the difficulty of X-pin motor manufacturing equipment has increased. X-pin motor equipment requires higher precision control and stricter process requirements.


With the implementation of the "dual carbon" strategy, green consumption has become a new trend in residents' consumption, and green and low-carbon has also become a key direction for the development of the automobile industry, accelerating the pace of the automobile industry's transformation to green.


Against this background, with the continuous development of new energy motor technology and the continuous optimization of production lines, X-pin motors will become a new trend in new energy motor in the future.


Honest Automation has developed X-pin motor automation equipment, which can provide semi-automatic and fully automatic winding and assembly according to customer process requirements. If customers need to prototype samples, our technical team can provide detailed equipment solutions. Honest Automation is committed to becoming a consultant to customers and helping them improve their production efficiency.

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