Rare Earth Magnet And Seven Types Of Motors
Rare Earth Magnet in Motors

Rare Earth Magnet And Seven Types Of Motors

Sean Zhang Sean Zhang

Sean Zhang

Zhejiang Innuovo Magnetics Co.,Ltd

发布日期: 2022年9月13日
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There are 7 types of motors used in electric vehicles. There are brushed DC motors, brushless DC motors, permanent magnet synchronous motors, induction motors, switched reluctance motors, synchronous reluctance motors and axial flux ironless permanent magnets motor. And Rare earth magnet is the most important part in the motors.

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A brushed DC motor is the simplest type of DC motor that uses brushes to transfer current to the motor windings through mechanical commutation. The armature or rotor is an electromagnet and the magnetic field is a permanent magnet. This motor does not require a controller to operate or change speed, and provides maximum torque at low speeds. The disadvantage is that the structure is bulky, the efficiency is low, the brush will generate heat and lead to low efficiency, and the heat is difficult to remove in the center of the rotor. Therefore, brushed DC motors are no longer used in electric vehicles.

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Brushless DC motors with permanent magnets are called brushless because they have no commutator and brushes. It adopts electronic commutation, is maintenance-free, has the traction characteristics of large starting torque and efficiency as high as 95%-98%, and is suitable for high power density design. This traction characteristic makes brushless DC motors widely used in electric vehicles, suitable for small cars with a maximum power of 60 kW. Disadvantages are the limited range of constant power, the decrease in torque with increasing speed, and the high cost of permanent magnets. The Toyota Prius uses a brushless DC motor.

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Permanent magnet synchronous motors have permanent magnets on the rotor, which have high power density and high efficiency traction characteristics, can be used for higher power ratings, and are therefore more expensive than other motors. This motor can work in different speed ranges without the need for a gear system. It is efficient and compact for in-wheel applications and also has high torque at low speeds. The disadvantage is that the iron loss is serious when running at high speed in the hub. At present, permanent magnet synchronous motors are mostly used in hybrid and electric vehicles, such as Chevrolet Bolt, Ford Focus, Nissan Leaf and BMW i3.

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Induction motors do not produce high starting torque at fixed voltage and fixed frequency like DC motors. But this can be changed using various control methods such as vector control or field oriented control. With these control methods, the maximum torque required for traction can be obtained when the motor is started. The squirrel cage induction motor has less maintenance and long service life, and the design efficiency can reach 92%-95%. The disadvantage is that a complex inverter circuit is required, and the motor control is difficult. Due to their low cost, induction motors are the first choice for high-performance electric vehicles. The Tesla Model S is the best example to demonstrate the high performance of induction motors. This motor is also used in the Toyota RAV4 and GM EV1.

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Switched reluctance motor is a type of variable reluctance motor with double significance. The structure is simple and strong, and the rotor is a laminated steel sheet without windings or permanent magnets. This reduces rotor inertia and helps improve acceleration. The robustness makes this motor suitable for high-speed applications and offers high power density. The disadvantage is that the control is complicated, and the addition of switching circuits will also bring noise. Synchronous reluctance motor is a synchronous motor with reluctance properties. The torque is caused by the difference in the reluctance of the rotor's alternating and direct axes, without excitation windings or permanent magnets. This type of motor is increasingly popular in electric and hybrid vehicles due to its simple and robust construction. The advantage is that there is no rotor loss, and it can provide higher permanent torque than an induction motor of the same size.

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Axial flux ironless permanent magnet motors are the most advanced motors for electric vehicles. The outer rotor has no slots, so no iron core is required. It also has no stator core, so it is light in weight. The radial component of the air gap magnetic field provides higher power density. The rotor of this motor can be mounted on the wheel side, and the stator windings are placed on the shaft. The slotless design results in less copper loss, high efficiency and more free space. The Renault Coupe uses this motor.

Marcus Zhou

Sales Engineer - Filter Press |Process Filtration | Dewatering | Solid-Liquid Separation

2 年

Nice knowledge share!!

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