What is a hub motor
Generally speaking, the motor installed in the rim is called the hub motor, and the English is called In-WheelMotor. But the hub motor has recently emerged in many forms. It is difficult to clearly define which type of motor is a standard hub motor.
From the type of motor, the hub motor has an axial magnetic field type (disc motor) and a radial magnetic field motor (ordinary motor). The former has a higher torque density and a more compact structure, but the cost is also higher and the manufacturing is difficult.
In the ordinary motor, the early hub motor is mainly dominated by the outer rotor, and now the structure of the inner rotor appears more and more.
The motor structure of the outer rotor has a large air gap and a large torque density, and is suitable for being flat, and is generally used in a direct drive type structure. The inner rotor motor is relatively slender, generally exerts its speed advantage, and then uses a reducer to decelerate and then drive the hub. The former takes the route of high torque density, and the latter takes the route of high power density. The former is simple in structure but economically inferior to the latter.
Direct drive and non-direct drive are two completely different technical routes. The direct drive motor torque is very large and the speed is very low. Generally, the maximum speed of the passenger car does not exceed 2000 rpm, and the commercial vehicle does not exceed 1000 rpm. Instead of a direct-drive motor, in order to take advantage of power density, reduce motor cost, and compensate for the cost of the reducer, the speed is generally high. For example, NTN has mentioned the motor speed to 15000 rpm.
On the other hand, from the perspective of product form, some wheel hub motors have brake systems, while others have no brakes. With the brakes, it represents the trend of the development from the single motor to the drive system. The improvement of integration and perfection shows that the application of the product is more mature.
The increase in integration is also reflected in the integration of the drive and the motor. Early product drivers were external, and today's drives are increasingly built into the motor.
The above picture shows the 80kw outer rotor hub motor provided by Protean. The whole motor consists of 8 sub-motors, each with built-in drive modules. This makes the electrical interface with the outside world greatly simplified. Not only that, this kind of motor is a highly redundant motor, and the damage of one or two sub-motors does not affect the safe operation of the vehicle.
