Application and characteristics of Axial straight-through Motor in the Field of Energy Saving [Electric opportunity]

At the 2021 China International Motor Industry chain Annual meeting hosted by Shanghai Nonferrous Network (SMM), Dr. Chen Zhengmin of Tongling hard Core Motor Technology Co., Ltd. introduced the application and characteristics of axial straight-through motor in the field of energy saving. He pointed out that the copper of the axial flux motor is 80% of that of the traditional motor, the corresponding copper consumption is 80% of the conventional motor, the consumption of silicon steel sheet is 20% of that of the conventional motor, and the iron consumption is 20% of that of the conventional motor. Therefore, the motor efficiency can be greatly improved, even exceeding the national level of energy efficiency.

Motor classification and industry background

Induction motor: at present, 80% of the motors in the domestic market are induction motors, also known as induction motors. The induction motor industry is mature and the quality is mixed in the stage of cost competition. The structure of induction motor is reliable, but its efficiency is generally low. Most of them are national level 3 energy efficiency, which consumes a lot of electricity. Due to the lack of rare earth permanent magnets in foreign countries, induction motors are also the mainstream motors abroad.

Permanent magnet motor: the product is mature and the efficiency is the highest among all motor types. After the price reduction of rare earth permanent magnets in 2010, it began to be popular. Most of the foreign high-end motors are permanent magnet motors. Domestic permanent magnet motor has become the mainstream trend, used in energy-saving substitution, high-end equipment industry. Permanent magnet motors in Jiangsu, Zhejiang, Shandong and Guangdong provinces are more popular, and other provinces need to be promoted.

Axial flux permanent magnet: axial flux motor belongs to permanent magnet motor. After its structure is improved, it has the advantages of small size, light weight and higher efficiency.

The structure of axial flux motor has evolved through three stages:

In the early stage (20-30 years ago): single rotor and single stator structure, due to unilateral magnetic tension, bearing life is a defect;

Mainstream (20 years ago): there are more than a dozen companies at home and abroad with double stators on both sides and single rotor at home and abroad. The advantage is light weight and the disadvantage is that the efficiency is lower than that of traditional permanent magnet motors due to technological problems.

Leading (10 years ago): double rotors on both sides and single stator in the middle, with unyoked stator structure, the lowest in the weight industry and the highest efficiency. At present, there are only three companies in the world: YASA in the United Kingdom (acquired by Mercedes-Benz in 2021) and hard-core motors in China by EMRAX, in Slovenia.

Technical advantages of axial flux motor

Basic comparison:

Small size: the outer diameter of the motor is the same as that of the traditional motor, and the axial length is the same as that of the traditional motor, which is very flat, saving installation space and convenient for design and layout.

Light weight: axial flux motor, the weight is the market ordinary induction motor, permanent magnet motor 1 beat 3 to 1 hand 4, easy to install and transport;

High efficiency: efficiency is generally higher than or equal to imported motors (ABB, Siemens, Panasonic, Anchuan and other brands), meet the national first-class energy efficiency, European IE5 standards. In the energy-saving tests of conventional water pumps and fans, it is about 15% and 25% more energy-saving than induction motors at all power levels.

Technical advantages of axial flux motor

Efficiency analysis:

The loss of motor mainly comes from copper consumption and iron consumption.

At the same current density, the less the amount of copper is, the smaller the copper consumption is, and the less the amount of iron is, the smaller the iron consumption is.

The copper of the axial flux motor is 80% of that of the traditional motor, the corresponding copper consumption is 80% of that of the traditional motor, the consumption of silicon steel sheet is 20% of that of the traditional motor, and the iron consumption is 20% of that of the traditional motor. Therefore, the motor efficiency can be greatly improved, even exceeding the national level of energy efficiency.

Application advantage description:

Lightweight and small size, suitable for equipment and vehicle design layout, lightweight high-efficiency motor helps to improve battery life and save battery costs.

For some products, motor weight is the main item, motor lightweight will halve the product weight and volume, and reduce transportation and installation costs:

The efficiency of the motor has increased from the traditional third-level energy consumption to the first-class energy consumption, with an energy saving of 15% Mel 255%. For large-scale enterprises with annual electricity bills of 2 million-200 million, the annual savings in electricity costs in pumps, fans, air compressors and production equipment are comparable to equipment investment.

The axial flux motor is suitable for large torque and is used in direct drive situations. Direct zone movement without transmission system, there are two advantages: high precision, can be used for precision equipment direct drive control (DDR motor). High efficiency, small size, can be used for large cooling fans, large industrial ceiling fans, large water-cooled cooling towers, and can also be used for conveyor belt direct drive motors in factories and mines.

Compact high-power motor: a few hundred kilowatts motor is only 100 kilograms, which is the 1x5-1pump6 of the exclusive motor, and the weight is lighter: megawatt motor, used in ship drive, large generator sets, and wind turbines. Compared with the traditional motor, the installation space of the axial flux motor is small, and the transportation is convenient.

Axial flux motors also have other advantages:

Servo control precision is high, there is a special design to ensure smooth torque, used for precision equipment.

Reliability: heat and cold resistance, insulation, waterproof, dustproof, anticorrosion, etc., according to the application needs to configure the corresponding structure and materials. Life design: according to the load requirements, the selection of motor bearings and anti-corrosion coating to ensure the life of the package machine.

The control mode is the same as the traditional permanent magnet motor, and the traditional controller can be used directly.

Sealing level: from IP21 to IP68, the corresponding sealing structure is designed according to the application requirements.

Heat dissipation scheme: depending on the application scenario and power level, it can be configured as water cooling, oil-cooled submersible cooling, coaxial air cooling, forced air cooling, and passive heat dissipation.

Anti-seismic design: to prevent the impact of vibration on the reliability of the motor during use and transportation.

Safety protection design and so on.

Distribution of intellectual property rights in industry

Source patent:

The patent of contemporary dual-rotor yoke-less axial flux motor was first applied by British and American researchers from 1998 to 2001. These patents define the basic structure of the axial flux; all subsequent patents are their subordinate patents. The valid term of patent protection is 20 years, and these source patents have been invalidated. In other words, 1) the industry no longer has the root patents that dominate everything, 2) all patents can only be produced around structural detail innovation and application structure innovation, and 3) all possible motor structures and application innovations must be intensively produced to block competitors.

Competitor patents:

YASA has more than a dozen patents, which are written in detail around its product structure, but the scope of protection is limited to the structure it uses, and does not block other feasible structures and principles. Can only ensure that the operation of their own technical route will not be affected, there is no organization of patent walls for competitive defense.

YASA adopts soft magnetic powder metallurgical material SMC instead of silicon steel sheet, which is commonly used in motor. The optimal heat is that the process is simple, and the structure of disc motor which is extremely difficult to realize is transformed into a mass production scheme. However, the disadvantage is that the cost and performance of SMC is not as mature as that of traditional silicon steel sheet, which leads to high motor cost and slightly lower efficiency than the theoretical value.

Hard core motor patent:

The hard core motor uses traditional silicon steel sheet to make disc motor. Silicon steel materials are widely used in the industry, so the cost is low and the electromagnetic performance is high. But when hard core starts a business, the technology of making disc motor with silicon steel sheet does not exist, so the biggest achievement and challenge of hard core motor is to create a new stator and rotor process system (structure, material mold, forming equipment, assembly process technology, assembly equipment), creating a low-cost and high-efficiency branch of axial flux motor technology.

There are more than 80 issued and pending patents for hard core motors, which build patent walls around a variety of feasible core structures, processes and applications, and continue to raise patent barriers.

Definition: motor type, product line and industry solution

According to the structural and functional characteristics, motors are classified into several motor types: national standard general motor, servo control motor, special motor.

According to the application scene, the motor is classified into product line: water pump motor, submersible pump motor, high-speed pump motor, compressor motor, refrigeration compressor motor, explosion-proof motor, fan motor, large fan motor of high speed fan, deceleration drive motor, direct drive drive motor, direct drive servo motor, traction motor, low voltage vehicle drive motor, high voltage vehicle drive motor, direct drive hub motor, deceleration wheel hub motor, Deceleration multi-purpose motor, aviation drive motor, aero generator, generator.

The needs of various industries select the required models from these product lines to form industry solutions. Solutions include textile industry, food processing industry, building materials industry, Xineng original automobile industry, traditional automobile industry and so on.

Special topic: application of Axial Flux Motor in New Energy vehicles

Advantages:

High efficiency, increase service life, save battery costs: the measured efficiency of high-power new energy motor (80kw) can reach 97.9%.

Small size, easy to dry layout, can enhance baggage compartment and battery compartment space: the volume is only the size of an ordinary permanent magnet motor.

Light weight, weight loss: the volume is only 1x3 of the ordinary permanent magnet motor, and the motor weight of the rated 80kw is only 24kg.

High torque scheme: the motor adopts polyploid design, and the maximum torque is designed to 1200Nm-2000Nm.

Transmission system advantages: directly reduce the transmission ratio of the gearbox to reduce transmission loss; reduce gear speed, can reduce the cost of transmission system; can increase gear life; reduce motor and gear noise.

Lightweight advantage: the axial flux motor is used to improve the torque, but the weight is lighter than the high-speed motor with the same power: at the same time, it can reduce the weight of the gearbox.

YASA, an axial flux motor company based in Oxford, UK, was acquired by Mercedes-Benz in mid-2021 and plans to build a mass production plant in Berlin for mass production of new energy vehicles.

Tabular short board discussion:

Permanent magnet motors are classified according to the installation mode of magnets, which are divided into surface-mounted motors and embedded motors.

The permanent magnet motors of new energy vehicles are basically built-in motors, and the surface-mounted permanent magnet motors in other lines account for the vast majority. Under the same material, the same size and the same cost, the power and torque of the embedded motor are about 80% of that of the table type.

The embedded type has strong magnetic weakening ability and strong overspeed ability, which can reach the maximum speed of 12000~18000rpm when rated 3500rpm; the only weakness of table type is poor weak magnetic ability, when rated 4500rpm, the peak 5000rpm is more suitable, and the transmission speed is increased again, which requires huge magnetic weakening current and significantly reduces the efficiency.

Axial flux motors are all surface-mounted motors. Therefore, according to the demand of high-speed operating conditions of new energy, the axial flux motor does not match.

Resolution route:

Multi-gear gearbox is used.

The maximum speed of the fuel engine of traditional vehicles is not high, so the industry uses multi-speed gearbox to meet the high-speed demand.

In the field of new energy, General Motors, Mobil and Mercedes-Benz all have technical reserves to apply multi-gearboxes to new energy vehicles. This scheme is a simplified version of the fuel car gearbox, which can improve the service life (the motor always works in the efficient range) and increase the maximum speed (in high speed).

The high current controller is used to design the rated speed from 7200rpm to 9000rpm directly, at the cost of higher electric control cost. At present, Mavericks' high-speed electric motorcycle adopts this scheme.

The series and parallel windings are controlled by circuit breakers, and the speed is increased by adjusting the back EMF of the motor. The corresponding electric control needs to be developed.

Motor is the power heart of modern industry, axial flux motor can make Xinzhuang lighter, smaller and more energy-saving. The mission of the hard core motor is to fully empower various industries, so that China's manufacturing industry can open a breakthrough in terms of basic power, and contribute to China's becoming a world power.