Tesla Model 3: Why Permanent Magnet Motor Instead of Induction Motor?

Recently, more details of Tesla Model 3 were unveiled.

Certificate of Model 3 published by EPA   
According to EPA, Model 3 may be equipped with a battery pack of about 50-75kW/h, and the power of the rear wheel drive engine is rated as 258 HP, which is equipped with a three-phase permanent magnet motor.
The document from EPA reveals that, the battery pack of upgraded Model 3 has a total voltage of 350 volts and a total capacity of 230 amperes, indicating that the adopted battery pack is of 80.5 kW/h. However, Elon Musk, the CEO of Tesla, earlier confirmed that the standard battery pack for Model 3 is 50kW/h, and the extended range is around 220 miles (354 kilometers), while the upgraded will be equipped with 75kW/h ones. Therefore, 80.5kW/h may be a maximum capacity instead of actual availability.
The power of the rear wheel drive engine of Model 3 is rated as 258 HP, which is lower than that of standard Model S and Model X. According to reports, ultra-sport and twin-engine Model 3 that are coming out next year will be more powerful.

Model 3 abandons induction motor

                                      Schematic diagram of three-phase induction motor
Previously, Model S and Model X were equipped with three-phase induction motor, which is a kind of asynchronous motor. The original intention for Tesla to choose induction motor may be concerned with less suppliers at the early stage when it was founded. Certainly, low cost and effective high speed range are main reasons. The cooperation between Tesla and Fukuta creates a breakthrough on the performance of three-phase induction motor.
When people believed that Tesla would follow the tradition of using induction motor, it chose three-phase permanent magnet motor for the newest Model 3.
Actually, as early as October 2016, Tesla has signed General Terms for Procurement of Tesla Spare Parts with Zhong Ke San Huan, a Chinese magnetic material company. The object of transaction is NeFeB magnet, and the term of the contract is 3 years, which indicated a new change in the selection of motor, and even rumored that Model 3 would change to permanent magnet motor that was confirmed by EPA now.

Why Permanent Magnet Motor?

Schematic diagram of permanent magnet motor

Although Tesla’s three-phase induction motor has merits of low cost, wide range of temperature endurance, broad range of output torque, and effective high speed range, but the defects of intensive energy consumption, lag of power factor, narrow high efficiency area, low light-load power, and worse adjusting performance cannot be neglected.
In the meantime, market demands more on permanent magnet motor. It is more efficient and has wider range of high efficiency area, smaller volume and lighter weight compared with three-phase induction motor. Efficiency, energy-saving and endurance are the most valued parts in current electric vehicle industry. The merits of permanent magnet motor fit the market more, and it is comparatively economical, which outweighs its defects of complicate control system and high cost, so Tesla chose it for its Model 3.
Tesla began to cooperate with Chinese suppliers since China is an important exporter of rare earth permanent magnet materials. It is reported that the enterprises in mainland China who cooperated with Tesla this time include Zhong Ke San Huan (NeFeB magnet), Zhixin Eletric (copper rotor), DMEGC (soft magnetic materials), NBTM (PM parts), Hota Industrial (under-driving gear set), Xusheng (gearbox casing), GEM, Hanrui Cobalt, and HBXG (iron powder, copper powder, nickle powder and cobalt powder).
There is still no more details and parameters of three-phase permanent magnet motor, but please keep close eyes on Vehicle Trend and we will share the information at the first time!

Author: Faye
Date: August 22nd, 2017
Source: VehicleTrend

Back to Archive Automotive