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Advantages and disadvantages of hairpin motors in the development of new energy vehicles

Release time:2022/07/07

In recent years, the development of new energy electric vehicles   has greatly increased the threshold of automobile drive motors. As the   general trend of the motor industry, hairpin motors are actively deployed by OEMs and third-party manufacturers. The market size is expected to expand rapidly in the next few years. In the context of technological upgrades and   higher thresholds, the industry may usher in a reshuffle. Companies that deploy hairpin motors in advance will have a first-mover advantage in new markets and greatly increase their market share.

hairpin motor manufacturing technology.jpg 

Compared with traditional round wire motors, hairpin motors have many advantages, which are mainly reflected in: small size, high efficiency,   strong thermal conductivity, low temperature rise, and low noise.

 

1. Small size:

Under the same power, compared with the traditional round wire motor, the flat wire hairpin motor has a smaller volume, less material and   lower cost, or the same volume, the slot full rate is improved, and the power   density is improved.

The round wire becomes a flat wire. In theory, the copper filling can be increased by 20-30% under the premise of the same space. This also means that, somehow, the power is increased by 20-30%. In other words, when the power is the same, the outer diameter and volume of the motor are   reduced, thereby reducing the amount of motor material.

 

2. Better temperature performance:

The interior of the flat wire hairpin motor is more compact and has fewer gaps, and the contact area between the flat wire and the flat wire   is larger, and the heat dissipation and heat conduction are better; at the same time, the contact between the winding and the core slot is better, and the heat conduction is better. The motor is very sensitive to heat dissipation and temperature, and the improved heat dissipation also brings   about an improvement in performance.

In some experiments, through temperature field simulation, it is concluded that the temperature rise of the flat wire motor with the same   design is 10% lower than that of the round wire motor. In addition to better thermal performance, some other properties, including temperature-related,   can be improved.

 

3. Less noise

The flat wire hairpin motor can make the rotor have better rigidity and restrain the noise of the rotor.

In addition, a relatively small notch size can also be used to effectively reduce the cogging torque and further reduce the electromagnetic   noise of the motor.

 

4. The ends are shorter

The end refers to the part of the copper wire outside the slot. The copper wire in the slot plays a role in the work of the motor, while the   end does not contribute to the actual output of the motor, but only plays a   role in connecting the wire between the slot and the slot. . The traditional   round wire motor needs to leave a long distance at the end due to process   problems, which is to prevent the copper wire in the slot from being damaged   during processing and other processes, and the flat wire motor fundamentally   solves this problem. Since copper wires are all hard wires, it is not   necessary to leave a section at the end during processing, and a shorter end   can save copper and improve efficiency.

 hairpin motor assembly line.jpg

The most important processes in the production of hairpin flat   wire motors are coil forming, twisting, welding and other technologies. The   winding of the flat copper wire motor can be divided into three types: I-pin,   Hair-pin, Wave-pin, etc. according to the shape of the flat wire, because   many automobile manufacturers have strict requirements on the external dimensions of the drive motor, and the Hair-pin motor The copper wires at the   ends of the motor are more closely arranged radially, so more than 90% of the   manufacturers currently choose to use Hair-pin motors, that is, the windings   are first shaped like hairpins, inserted into the stator slots, and then put   on the other end. The ends of the "hairpin" are welded together. However, flat wire motors represented by Hair-pin have high barriers in terms of production process, equipment and raw materials.

 

1. Production process:

More than a dozen processes are formed at one time. Flat wire   motors now mostly use the second-generation axial winding technology (such as   Hair-pin). The production process is many and complex, and the precision and stress of winding forming are extremely high. The key processes such as Hair-pin forming, automatic head twisting, etc. are technically difficult.   Large, more than a dozen processes need to be formed at one time, which increases the difficulty; and the AC impedance increases, and the conversion   efficiency decreases at high speed. At the same time, the "skin   effect" may occur in the process practice, resulting in wasted intermediate area, large surrounding current, obvious heat generation, and   reduced efficiency.

 

2. Serialized design is difficult:

The design scheme is not unified, and once the stator winding is determined, it is difficult to change, and the serialization is difficult.   Different car companies have different design solutions, and the stator is the core of motor design. After the stator size is finalized, if the wire shape and size change at any point, expensive tooling and molds need to be customized, and the compatibility is low.

 

3. Production equipment:

Flat wire motor production equipment has high requirements and   mainly relies on imports. Flat wire motors have high requirements on product   consistency and are technically difficult, and require investment in high-precision automated servo equipment, welding equipment, Hair-Pin wire forming equipment and tooling molds. The investment of flat wire motor production line is 2-5 times that of round wire.

 

4. Production raw materials:

Hairpin motors have correspondingly higher requirements for upstream copper wires, coatings and other raw materials. The enameled flat   copper wire is the core component of the flat wire motor. Depending on the power, the usage of a drive motor is about 7-10kg, accounting for about 17%   of the overall value of the flat wire permanent magnet motor. Another problem   brought about by the upgrade of round wires to flat rectangular cross-section wires is that the wire manufacturing technology in the upstream of the industrial chain also needs to be innovated simultaneously.

 

5. The difficulty of coating flat wire increases:

The copper wire must be elastic, but the magnet wire insulation layer should not be damaged by rebounding after bending; the flat wire will shrink unevenly after the insulation coating is dried, and it is easy to deform and thin the four corners, which affects the insulation and needs to be improved. Thicker coating thickness at the R corner; it is difficult to coat the paint film at the R corner of the flat wire, and it is difficult to ensure the uniformity of the insulating layer; and after the flat wire is bent into a hairpin, the stress at the R corner is concentrated, which is easy to cause coating The layers are damaged, so the precision and quality of the copper wire and its coating are very high.

hairpin motor manufacturing line.jpg  

In response to the above problems, NIDE Group has continuously developed and innovated, and has provided customers with different types of hairpin motor manufacturing solutions to solve various technical problems encountered in motor manufacturing. We focus on the R&D and supply of   motor manufacturing equipment, and provide completed motor manufacturing lines and motor assembly lines, which are used in the automotive industry,   home appliance industry, aviation, agriculture, industry and other fields.


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