1. DC brushed motor
DC brushed motors have a simple structure and mature technology, possessing superior electromagnetic torque control characteristics unmatched by AC motors. Therefore, until the mid-1980s, they remained the primary research and development focus for electric vehicle motors both domestically and internationally. However, the high price, large size, and heavy weight of DC motors limited their application in electric vehicles.
2. Permanent magnet brushless motor
Permanent magnet brushless motors can be divided into brushless DC motor systems driven by square waves (BLD-CM) and brushless DC motor systems driven by sine waves (PMSM). Both have high power density, and their control methods are basically the same as induction motors. Their main advantage is that their efficiency can be 6 percentage points higher than that of AC induction motors. Therefore, they are widely used in electric vehicles and are currently a hot research topic in electric vehicle motor development. These motors have high energy density and efficiency, small size, low inertia, and fast response, making them very suitable for electric vehicle drive systems and showing excellent application prospects. However, they are relatively expensive, and permanent magnet materials are generally only heat-resistant below 12°C. Currently, electric vehicles developed in Japan mainly use this type of motor.
3. AC induction motor
AC induction motors were among the earliest types of motors used in electric vehicles. Their speed control technology is relatively mature, and they offer advantages such as simple structure, small size, light weight, low cost, reliable operation, low torque ripple, low noise, high speed limits, and no need for position sensors. However, due to their small speed control range and less-than-ideal torque characteristics, they are not suitable for electric vehicles that require frequent starts and decelerations. Electric vehicles developed in the United States and Europe primarily use this type of motor.
4. Switched reluctance motor
Switched reluctance motors (SRMs) offer advantages such as simplicity, reliability, efficient operation over a wide speed and torque range, flexible control, four-quadrant operation, fast response, and low cost. However, practical applications have revealed drawbacks, including large torque ripple, high noise, and the need for position detectors, thus limiting their application.
Each of the four types of motors mentioned above has its own advantages and disadvantages. However, for electric vehicles, since electrical energy is provided by various types of batteries, which are expensive and precious, it is more reasonable to use the most efficient permanent magnet brushless motor. It has been widely used in modern electric vehicles with power less than 100kW.
Increasingly, electric vehicles abroad are adopting advanced electric wheels (also known as in-wheel motors). These motors (mostly permanent magnet brushless motors) directly drive the wheels, eliminating the complex mechanical transmission components of traditional automobiles such as gearboxes, drive shafts, and drive axles, greatly simplifying the vehicle's structure. However, this requires the motor to have high torque at low speeds, especially for military off-road vehicles, where the ratio of base speed to maximum speed must be 1:10. In recent years, the United States, Britain, France, Germany, and other countries have applied electric wheel technology to military off-road vehicles and light tanks, achieving significant results.
