**Deep Understanding of the Internal Structure of an Electric Motor**
Many riders are not very familiar with the internal components of an electric motor. In this article, we will take you inside the motor to explore what lies beneath its surface.
Starting with the magnets—something that car enthusiasts care a lot about. There are several types of permanent magnets used in motors, such as ferrite, alnico, and neodymium-iron-boron (NdFeB). Among these, NdFeB is the most powerful and widely used in modern electric vehicles due to its high magnetic energy product, which allows for smaller, more efficient motors. These magnets are typically sold by grade, with common classifications including EH, UH, SH, H, M, and N, from highest to lowest quality. Each grade has a corresponding temperature resistance rating, like 200°C, 180°C, and so on. The higher the temperature resistance, the better, as excessive heat can cause demagnetization, reducing the motor’s lifespan.
The numerical values that often accompany these grades, such as 35, 38, or 40, indicate the magnet's strength. The higher the number, the stronger the magnet. Most modern motors use 38M-grade magnets, which offer a good balance between cost and performance. However, some manufacturers still use H-grade magnets, though they are less common.
Next, the thickness of the magnets also plays a role in their performance. Thicker magnets tend to resist demagnetization better under high temperatures. For example, a 3 mm thick magnet may lose less than 3% of its strength after two hours at 100°C, while a 2.5 mm thick one could lose up to 5–8%. This shows that thickness matters more than width when it comes to magnet performance.
Moving on to the iron core, which is made from silicon steel sheets. These sheets are usually cold-rolled and come in different grades, such as 800, 600, 470, 400, 350, and 300. The numbers represent the iron loss value per kilogram. Lower numbers mean better performance, as less energy is lost as heat. High-quality steel, like that from WISCO or Baosteel, tends to be more expensive but offers better efficiency. Imported materials from Germany or Japan are even better, though they are rarely used in mass-produced electric motors.
Then there’s the enameled wire, which is essential for winding the motor’s coils. Common types include 130-2 and 180-1. The first number refers to the temperature resistance, with 180 being superior to 130. The second number indicates the paint film thickness, where -1 means thinner and -2 means thicker. Using 180-1 enameled wire generally results in better performance and longer life.
The lead wires, or “eight-core lines,†are another important component. Their cross-sectional area determines how much current they can handle. For example, motors under 800W usually use 1.5 mm² wires, while those over 1500W may require 6 mm² or larger. If a 1500W motor only uses 1.5 mm² wires, it might be overrated, as the wires could easily overheat and burn out.
Finally, let’s talk about bearings and Hall sensors. Bearings support the motor’s rotating parts and must be strong enough to handle the torque. A typical 1500W motor needs at least a 6004 bearing, with an outer diameter of 42mm. Larger motors require bigger bearings to handle increased load. Bearings are rated by their precision (Z1-Z4), with Z4 being the highest quality and most expensive. While premium bearings like those from Havalo or other brands exist, they are rare in consumer motors due to their high cost.
Hall sensors act as the "door" between the motor and controller, controlling the commutation process. Properly designed and matched controllers reduce the risk of Hall sensor failure. However, if the controller overheats and cuts off the signal, the motor may continue running as a generator, potentially damaging the Hall sensor if it stops at the wrong position.
In summary, understanding the internal structure of an electric motor helps users make more informed decisions when choosing or maintaining their vehicles. From magnets to bearings, every component plays a crucial role in the motor’s performance and longevity.
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