Why flat wire motors are more suitable for new energy vehicles than round wire motors?

AIP shares with you the"Why flat wire motors are more suitable for new energy vehicles than round wire motors?".

December 26, 2023

Why flat wire motors are more suitable for new energy vehicles than round wire motors?

The difference between flat wire motors and round wire motors lies in the way the copper wires are shaped. Flat wire is conducive to the improvement of the slot fullness of the motor, generally, the slot fullness of round wire motors is about 40%, while the slot fullness of flat wire motors can reach more than 60%. The increase in slot fullness means that under the premise of the space remains unchanged, more copper wires can be filled, generating stronger magnetic field strength and increasing power density.

Flat wire motors are a new type of drive motor with flat rather than round wires, but they are not a novelty, having appeared in the industry decades ago.

However, the use of flat wire motors in new energy vehicles is a recent thing. So how exactly does a flat wire motor work? And how does it realize those advantages? Next, this article will be from several aspects to introduce the flat wire motor in detail.

Ⅰ.What is a flat wire motor?

Flat wire motor is not a new concept, its development has been a long time, decades. Initially, it is mainly used in the industrial field of high-power motors and generator sets, because these occasions require high power and efficiency of the motor.

Later, the new energy automobile industry gradually emerged, and flat wire motors also began to be applied to the field of vehicles. Many applications in vehicles use flat wire motors, such as automotive generators, starters, EPS (electric power steering) motors, main drive motors, P2 (parallel hybrid) system motors, and so on!

Ⅱ.The advantages of making the wire "flat".

So, what are the advantages of flat wire motors in new energy vehicles? Next will be analyzed from the following aspects:

First of all, the slot full rate refers to the proportion of copper conductor filling in the stator slot of the motor. Flat wire motors use copper strips instead of copper wires, resulting in more copper conductors in the slots, which increases the slot fullness ratio. What's the benefit of this?

Imagine if you had to tie up a box with a piece of string, would you use one thick piece of string or several thin pieces? It would take less effort to use one thick rope because it would be able to wrap the box more tightly.

Similarly, the copper strips of a flat wire motor are like thick ropes that wrap more tightly around the stator teeth. This allows for less magnetic field leakage and reluctance, increasing the flux and torque of the motor.

Secondly, power density and efficiency refer to the power or effect that the motor outputs per unit of volume or weight. Flat wire motors can output more power in the same or smaller volume and weight due to high slot fullness. This is very important for new energy vehicles because it means space and cost savings and improved energy and mileage.

Finally, noise and comfort refer to the impact of the motor's operation or vibration on people's senses. Flat wire motors work more efficiently at low speed and high torque or high speed and low torque operating conditions due to their high slot fullness.

This means that it can deliver more torque at lower speeds or less torque at higher speeds. This reduces noise or vibration caused by speed variations.

In summary, flat wire motors have the advantages of high slot fullness, high power density, and efficiency, good noise, and comfort compared to round wire motors.

These advantages make flat wire motors in the field of new energy vehicles have broad application prospects and market potential. So, how does the flat wire motor realize these advantages? What is its working principle?

Ⅲ.How the flat wire motor "flat" out of the advantages

Flat wire motor and round wire motor working principle is essentially no difference, are through the current in the magnetic field force to produce rotation. The difference is that the flat wire motor uses a flat rectangular wire instead of the traditional round wire. What is the advantage of this? We can understand this with a simple analogy.

Suppose you had to fill a box, leaving as little space as possible, would you choose a cylinder or a flat rectangle? If you choose the cylinder, then you will find that there are still many empty spaces in the box, and the cylinders cannot be closely aligned with each other. With a flat rectangle, there are almost no gaps between them.

Similarly, if you use flat rectangular wires instead of round wires, you can increase the slot fill ratio, which is the percentage of space in the slot that the coil takes up when it is placed in the slot because there are no gaps between the flat wires and there are gaps between the round wires.

What does a high slot fill rate mean? It means that a flat wire motor can fill 20-30% more wire in the same volume. This translates into an increase in the amount and strength of the magnetic field generated when current passes through the wires.

The stronger the magnetic field, the greater the torque (i.e., the ability to turn) that the motor produces. As a result, flat wire motors have a higher power density (i.e., power output per unit volume) and efficiency (i.e., the ratio of output power to input power) than round wire motors for the same volume.

In addition, flat wires have the advantage of reducing Pierce losses (i.e., eddy current losses due to AC in the winding) in the winding. This is because flat wires have a smaller cross-sectional area and greater circumference perpendicular to the winding axis than round wires.

In this way, in the alternating magnetic field to generate eddy currents across the cross-sectional area is smaller, larger circumference, greater resistance, the eddy current is smaller; and vice versa, the cross-sectional area is larger, the circumference is smaller, the resistance is smaller, the eddy current is larger. Therefore, under the same conditions, flat conductors have lower Pierce losses than round conductors.

To summarize, flat wire conductors make flat wire motors have higher slot fullness, power density, efficiency, and overload capacity under the same volume, which improves the energy and reliability of the motor. This is the working principle and advantages of flat wire motors.

Ⅳ.The use of flat wire motors

The advantages of flat wire motors are not only reflected in theory but also verified in practice. In the field of new energy vehicles, flat-wire motors have become the preferred drive motor of several well-known brands motor in different types of new energy vehicles in the specific application of the embodiment.

First, it is Schaeffler P2 motor. This is an integrated hybrid powertrain that integrates the flat wire motor, clutch, and gearbox into one compact module. This saves space and weight and increases installation efficiency and reliability.

The Schaeffler P2 motor utilizes high-efficiency flat-wire technology to achieve a power output of up to 120kW and a peak torque of 300Nm, which is also efficient at low speeds. Schaeffler P2 motors have been adopted by several luxury brands, including Audi, BMW, and Volkswagen, and have received favorable market feedback.

Next, there is the GM Volt generator. This is a plug-in hybrid vehicle that utilizes two flat-wire motors as the primary source of drive power with a small gasoline engine as a backup power generator.

The GM Volt generator utilizes the low-noise benefits of flat-wire technology to provide a quiet and comfortable ride in electric-only mode and can achieve a power output of up to 149kW and a peak torque of 370Nm, as well as smooth and fluid acceleration. The GM Volt generator has been sold in several markets, including, Europe and China, and has been recognized by consumers and professional reviewers.

Finally, take a look at the Toyota Prius drive motor. This is a globally recognized hybrid vehicle that utilizes a flat-wire motor as a secondary drive source and an Atkinson cycle engine as the primary drive source.

The Toyota Prius drive motor takes advantage of the high power density of flat-wire technology to provide greater power output and greater overload capacity for the same size and can achieve a maximum power output of 53kW and peak torque of 163Nm, providing adequate power support at low speeds.

Toyota Prius drive motors have been sold in more than 10 million units worldwide and have received numerous accolades from users and environmental organizations.

From these cases, it can be seen that flat-wire motors have become an important development direction for new energy vehicle drive technology, which not only improves the energy and efficiency of the vehicle but also reduces the cost and environmental impact of the vehicle. This is why the flat wire motor overnight from the hot potato into a favorite meat and potatoes!

Ⅴ.The difficulties faced by the flat-wire motor

Although the flat wire motor has many advantages, but not without disadvantages and difficulties. In actual production and application, flat-wire motors are also facing several technical difficulties and challenges, and the need for continuous research and improvement.

First of all, the manufacturing process of flat wire motors is relatively complex. Since the conductor cross-section of flat wire motors is rectangular rather than circular, more precision and skill are required in the winding process to ensure even spacing and alignment between the conductors and to avoid abrasion and damage between the conductors. In addition, the winding of flat wire motors also requires more materials and time, which increases the production cost and cycle time.

Secondly, the heat dissipation problem of flat wire motors is more prominent. The higher slot fullness of flat wire motors, leads to poor air circulation inside the windings, making it difficult to dissipate heat effectively.

At the same time, due to the higher power density of flat wire motors, more heat will be generated under high load conditions, which may lead to high winding temperatures, insulation aging, energy degradation, and other problems. Therefore, flat wire motors need to adopt better heat dissipation design and materials to ensure their stable and reliable operation.

Finally, there are some other challenges associated with flat wire motors. For example, the process of use may be subject to external interference or its failure to affect the control accuracy and effect; with other components being matched or compatibility problems; in the market, promotion may be encountered when the user recognition or acceptance of the degree is not high.

Conclusion: Through the introduction above, we can understand that the flat wire motor is a new type of drive motor, which has higher slot fullness, power density, efficiency, and overload capacity, as well as lower volume, weight, noise, and cost compared with the traditional round wire motor. These advantages make flat wire motors have a broad application prospect and market space in the field of new energy vehicles.

Therefore, why the flat wire motor overnight from the hot potato into a favorite meat and potatoes? The reason is that flat-wire motors are in line with the development needs and direction of the new energy automobile industry, which can provide a more efficient, energy-saving, comfortable, and environmentally friendly drive solution for new energy vehicles.

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