Tesla has just announced that the next generation of permanent magnet motors configured on their electric vehicles will not use rare earth materials at all!
Tesla slogan:
Rare earth permanent magnets are completely eliminated
is this real?
In fact, in 2018, 93% of the world’s electric vehicles were equipped with a powertrain driven by a permanent magnet motor made of rare earths. In 2020, 77% of the global electric vehicle market uses permanent magnet motors. Observers of the electric vehicle industry believe that as China has become one of the largest electric vehicle markets, and China has largely controlled the supply of rare earths, it is unlikely that China will switch from permanent magnet machines. But what is Tesla’s situation and how does it think about it?
In 2018, Tesla used an embedded permanent magnet synchronous motor for the first time in the Model 3, while retaining the induction motor on the front axle. Currently, Tesla uses two types of motors in its Model S and X electric vehicles, one is a rare earth permanent magnet motor and the other is an induction motor. Induction motors can provide more power, and induction motors with permanent magnets are more efficient and can improve driving range by 10%.
The origin of permanent magnet motor
Speaking of this, we have to mention how the rare earth permanent magnet motor came about. Everyone knows that magnetism generates electricity and electricity generates magnetism, and the generation of a motor is inseparable from a magnetic field. Therefore, there are two ways to provide a magnetic field: excitation and permanent magnet.
DC motors, synchronous motors and many miniature special motors all require a DC magnetic field. The traditional method is to use a energized coil (called a magnetic pole) with an iron core to obtain a magnetic field, but the biggest disadvantage of this method is that the current has energy loss in the coil resistance (heat generation), thereby reducing motor efficiency and increasing operating costs.
At this time, people thought – if there is a permanent magnetic field, and electricity is no longer used to generate magnetism, then the economic index of the motor will be improved. So around the 1980s, a variety of permanent magnet materials appeared, and they were then applied to motors, making permanent magnet motors.
Rare earth permanent magnet motor takes the lead
So what materials can make permanent magnets? Many netizens think that there is only one kind of material. In fact, there are four main types of magnets that can generate a permanent magnetic field, namely: ceramic (ferrite), aluminum nickel cobalt (AlNiCo), samarium cobalt (SmCo) and neodymium iron boron ( NdFeB). Special neodymium magnet alloys including terbium and dysprosium have been developed with higher Curie temperatures, allowing them to withstand higher temperatures of up to 200°C.
Before the 1980s, the permanent magnet materials were mainly ferrite permanent magnets and alnico permanent magnets, but the remanence of these materials is not very strong, so the magnetic field generated is relatively weak. Not only that, but the coercive force of these two kinds of permanent magnets is low, and once they encounter an external magnetic field, they are easily affected and demagnetized, which restricts the development of permanent magnet motors.
Let’s talk about rare earth magnets. In fact, rare earth magnets are divided into two types of permanent magnets: light rare earth and heavy rare earth. Global rare earth reserves consist of approximately 85% light rare earths and 15% heavy rare earths. The latter offers high temperature rated magnets suitable for many automotive applications. After the 1980s, a high-performance rare earth permanent magnet material-NdFeB permanent magnet appeared.
Such materials have higher remanence, as well as higher coercivity and energy production, but generally lower Curie temperatures than alternatives. The rare earth permanent magnet motor made of it has many advantages, such as high efficiency, no excitation coil, so there is no excitation energy loss; the relative magnetic permeability is close to that of the air machine, which reduces the motor inductance and improves the power factor. It is precisely because of the better power density and efficiency of rare earth permanent magnet motors that there are many different designs of electric drive motors, and the most popular are rare earth permanent magnet motors.
Tesla wants to get rid of
Dependence on Chinese rare earths?
Everyone knows that China provides the vast majority of rare earth resources in the world. The United States has also seen this in recent years. They do not want to be constrained by China in the supply of rare earths. Therefore, after Biden took office, he tried to increase his participation in the rare earth supply chain. It’s one of the priorities of the $2 trillion infrastructure proposal. MP Materials, which bought a previously closed mine in California in 2017, is vying to restore the U.S. rare earths supply chain, with a focus on neodymium and praseodymium, and hopes to become the lowest-cost producer. Lynas has received government funding to build a light rare earths processing plant in Texas and has another contract for a heavy rare earths separation facility in Texas. Although the United States has made so many efforts, people in the industry believe that in the short term, especially in terms of cost, China will maintain a dominant position in the supply of rare earths, and the United States cannot shake it at all.
Perhaps Tesla saw this, and they considered using permanent magnets that do not use rare earths at all as motors. This is a bold assumption, or a joke, we still don’t know. If Tesla abandons permanent magnet motors and switches back to induction motors, this does not seem to be their style of doing things. And Tesla wants to use permanent magnet motors, and completely abandons rare earth permanent magnets, so there are two possibilities: one is to have innovative results on the original ceramic (ferrite) and AlNiCo permanent magnets, The second is that the permanent magnets made of other non-rare earth alloy materials can also maintain the same effect as the rare earth permanent magnets. If it’s not these two, then Tesla is likely playing with concepts. Da Vukovich, president of Alliance LLC, once said that “due to the characteristics of rare earth magnets, no other magnet material can match their high strength performance. You can’t really replace rare earth magnets”.
Regardless of whether Tesla is playing with concepts or really wants to get rid of its dependence on China’s rare earth supply in terms of permanent magnet motors, the editor believes that rare earth resources are very precious, and we should develop them rationally, and pay more attention to future generations. At the same time, researchers need to increase their research efforts. Let’s not say whether Tesla’s formulation is good or not, at least it has given us some hints and inspirations.