Magnet-Free Electric Motor Prototypes: Valeo and MAHLE’s Inner Brushless Electrical Excitation Motor, Vitesco Technologies’ Externally Excited Synchronous Machine (EESM), and ZF’s In-Rotor Inductive-Excited Synchronous Motor (I2SM)

     Magnets made of neodymium, a rare earth element, are standard in most brushless electric motors. They are required for maintaining a high coercive field which is necessary for motor operation. However, there are now in the works, some new electric motor designs that do not need rare earth magnets. These new designs may offer improved performance, lower cost, reduced dependence on China for neodymium and neodymium processing, and significant decreases in overall carbon footprint.

MAHLE'S Magnet-Free Motor with Valeo's Inverter and Controls

     German mobility technology company MAHLE developed a magnet-free electric motor in the early 2020s. It was reported in a June 2021 article in AutoEvolution:

“It works by generating the required magnetic field using excitation copper coils located inside the rotor that replace conventionally used permanent magnets. The power is transmitted wirelessly, contact-free, and consequently wear-free.”

“The key part of the assembly is a wireless transmitter that uses an alternating field to send energy to the rotor. This field is then converted into direct current for the aforementioned coils, producing an additional magnetic field that enables the motor to generate torque.”

“According to Mahle, the ability to adjust the parameters of the rotor’s magnetism instead of being limited by the use of traditional magnets has led to maximum performance through the full range of operating speeds. It’s thus capable of achieving an efficiency above 96%,”

     Contact-free means little to no mechanical wear. Few moving parts means it is easy to service if it ever needs it. Other expected advantages are a lower-cost motor and an increased range. MAHLE noted then that they expect mass production to begin by the end of 2023.

 

MAHLE’s Magnet-Free E-Motor vs. Magnet E-Motors

     As explained in a 2022 article in GlobalSpec, conventional permanent magnet generators (PMGs) used in current EVs use neodymium magnets (usually) to create a magnetic field that can convert mechanical energy into electrical energy. The magnetic field is used to rotate the rotor which creates torque. The MAHLE magnet-free motor uses electromagnetic induction instead of a neodymium magnet to generate the magnetic field that provides the rotational energy. The process is more efficient than PMGs. Magnet-free motors also generate less electromagnetic interference (EMI). EMI can interfere with nearby electronic equipment. If these induction-based motors can be produced and provided to the EV industry and to other industries as well they have the potential to decrease costs, energy use, and emissions anywhere an electric motor is used.

 

Source: MAHLE

Valeo and MAHLE October 2024 Joint Development Agreement

     According to the October press release announcing the joint development agreement between Valeo and MAHLE:

“Valeo and MAHLE have joined forces to develop an innovative magnet-free electric axle system, targeting upper segment electric vehicles with peak power ranging from 220 kW to 350 kW. Introducing the iBEE system (inner Brushless Electrical Excitation), this cutting-edge technology aims to revolutionize performance and efficiency of magnet free electric motor.’

Valeo provides expertise with electric motors, highly efficient inverters and associated controls. MAHLE provides expertise on a magnet-free rotor with its MAHLE Contactless Transmitter (MCT) technology.

“Valeo and MAHLE are working on an innovative cooling concept in order to achieve an outstanding continuous to peak power ratio.”

Valeo notes that testing of the first prototypes will be finished by the end of this year. Valeo’s new stator and cooling technology could potentially increase power density by 30% over current numbers. In 2020 MAHLE built a test bench in Fellbach/Germany for electric drives in order to develop and test e-axles and e-drive units for a wide range of electric and hybrid vehicles. They describe the Valeo/MAHLE partnership as a collaborative breakthrough.

“The motor's design incorporates Mahle's Magnet-free Contactless Transmitter (MCT) system, which enables energy transfer from the battery to the rotor through induction, eliminating the need for physical contact. This innovative approach not only removes the requirement for rare earth magnets but also promises enhanced longevity due to reduced mechanical wear.”

“Valeo's contribution includes a high-performance inverter and advanced motor control technology, integrated seamlessly with Mahle's rotor design. This synergy has resulted in a motor that not only matches but potentially surpasses the performance of traditional permanent magnet motors.”

To summarize, the new e-motor includes:

・Magnet-free design

・Induction-based energy transfer

・High efficiency (over 95%)

・Exceptional durability due to reduced mechanical wear

・Power output of up to 350 kW

     It is estimated that the carbon footprint of the vehicles in which the motor is used will be reduced by more than 40%. The life-cycle environmental impacts will also be reduced significantly as well as dependence on China for materials and materials processing. This collaboration and magnet-free e-drives in general, may have lasting impacts on EV design and may be able to be used for electric motors in many applications, including household appliances and industrial machinery. It could also reduce e-waste, resulting from the efficiency increase, I believe.

 

 

Vitesco Technologies’ Externally Excited Synchronous Machine (EESM)

     Vitesco Technologies, now part of Schaeffler Group AG, was an early developer of axle-drive EV electric motors. The graphics below compare their magnet-free externally excited synchronous machine (EESM) to permanent magnet synchronous machines (PMSMs). EESMs beat PMSMs in sustainability (due to no need for a magnet) and costs. They equal them in peak power but trail them in continuous power and they are slightly less efficient. That decrease in efficiency can take away some of the sustainability advantages since decreased efficiency=higher emissions. EESMs can provide more power and constant power at higher speeds. The last graphic shows different configurations. Two of the three utilize PMSMs for part of the drive, one for main drive and one for auxiliary drive. They ask if EESMs will replace PMSMs. If the Valeo/MAHLE motor can run at efficiencies exceeding those of PMSMs, then that will be the likely technology solution.

Advantages

·        High efficiency at WLTC and highway driving

·        High power density

·        Innovative rotor cooling enables high torques and efficiency

·        Minimized cost and supply chain risk, increased sustainability by optimized CO2-footprint

·        Universally applicable

·               Space neutral rotor power supply

Features

·         Adaptable rotor field

·         High slot fill factor due to optimized needle winding process

·         Effective rotor cooling due to slot cooler close to the winding

·         No rare earth magnets

·         Scalable design

·                 High integrated, non-contract rotor power supply

 

 

ZF’s In-Rotor Inductive-Excited Synchronous Motor (I2SM)

     ZF has developed a magnet-free electric motor that “transmits the energy for the magnetic field via an inductive exciter inside the rotor shaft. This makes the motor uniquely compact with maximum power and torque density.” They believe their design offers a significant improvement over EESM motors:

“Compared to common SESM systems {EESMs}, the inductive exciter can reduce losses for the energy transmission into the rotor by 15 percent.”

     Something that all of these magnet-free motors offer is increased efficiency at fast highway speeds. This is due to the elimination of drag losses.

“To ensure that the magnetic field in the rotor is built up by current instead of magnets, the conventional SESM concepts currently still require sliding or brush elements in most cases, which force compromises: A dry installation space, i.e. not accessible for oil cooling and with additional seals, is necessary. As a result, conventional SESMs take up around 90 mm more space axially. As a result, manufacturers generally cannot flexibly vary between PSM and SESM variants in their model planning without additional effort.”

“In order to offer the advantages of separately excited synchronous machines competitively, ZF has succeeded in compensating for the design-related disadvantages of common separately excited synchronous machines. In particular, the torque density has been significantly increased compared to the state of the art thanks to an innovative rotor design. The space-neutral integration of the exciter into the rotor means that there are no axial space disadvantages. In addition, an increase in power density in the rotor leads to an improvement in performance.”

     The I2SM is a brushless induction motor design (as is the MAHLE motor).

     ZF recently launched a new 800V Test & Validation Laboratory in the UK.

“The main aim is to accelerate the adoption of 800V architectures with improved efficiency, charging and vehicle performance advantages for electric vehicles (EVs).”

They will also offer validation testing to third parties and work with Tier 1 suppliers and OEMs. Most current EVs are based on 400V architecture. 800V architecture offers faster charging times (10 minutes vs. 20 minutes) and lighter, less expensive, lower gauge wiring. If combined with “Silicon Carbide MOSFETs, up to 10 percent efficiency gains are possible, which could ultimately lead to downsized batteries or improved vehicle range.” ZF is also developing these motors for better hydrogen fuel cell FCEVs.

     It should be interesting to see which motor designs win out and get mass-produced, how the industry is impacted, what are the final improvement numbers on overall efficiency, overall cost, and overall emissions reduction, and what happens regarding further improvements.

 

References:

IBee: Really? This magnet-free engine could reduce the carbon footprint by 40%. Samir Sebti. Daily Galaxy. October 28, 2024. IBee: Really? This magnet-free engine could reduce the carbon footprint by 40%

Valeo and MAHLE expand their product range of magnet free electric motors to upper segment applications through a Joint Development of iBEE (Inner Brushless Electrical Excitation). Valeo. Press Release. October 14, 2024. Valeo and MAHLE expand their product range of magnet free electric motors to upper segment applications through a Joint Development of iBEE (Inner Brushless Electrical Excitation) | Valeo

Externally Excited Synchronous Machine (EESM) as Main and Auxiliary Drive. Dr.-Ing. Gerd Rösel, Nico Daun, Artur Giedymin, Dragan Stojkovic, and Matthias Töns. Vitesco Technologies. April 28, 2023. Vitesco Technologies Standard Presentation

No need for rare earths: Vitesco Technologies presents electric drive for maximum sustainability. Vienna Motor Symposium 2023. Vitesco Technologies. April 27, 2023. Vitesco Technologies - 23-04-27

Electric drives for every application. Mahle. Electric Drive Systems - MAHLE Group

Mahle’s Innovative Magnet-Free EV Motor: How It Works and Why It’s a Big Deal. Auto Evolution. June 8, 2021. Mahle’s Innovative Magnet-Free EV Motor: How It Works and Why It’s a Big Deal - autoevolution

ZF Develops Magnet-Free Electric Motor. Power Transmission Engineering. September 1, 2023. ZF Develops Magnet-Free Electric Motor | Power Transmission Engineering Magazine

ZF’s new 800V Test & Validation Laboratory in the UK unlocks benefits for next-generation mobility. ZF Group. Press Release. October 14, 2024. ZF’s new 800V Test & Validation Laboratory in the UK unlocks benefits for next-generation mobility - ZF

Highly efficient magnet-free electric motor. Ryan Clancy. GlobalSpec. November 30, 2022. Highly efficient magnet-free electric motor | GlobalSpec

Permanent Magnet Generators. Electricity Magnetism. Permanent Magnet Generators | How it works, Application & Advantages

Electrically Excited Synchronous Machine. Shaeffler. Electrically Excited Synchronous Machine | Schaeffler Group USA Inc.