In the era of new energy, truck engines have been replaced by drive motors. Although electric motors are widely used in industrial applications, they are relatively new in trucks. Most truck enthusiasts have a more limited understanding of them compared to traditional engines. In this issue, I will use the Fast Sunzon flat-wire motor as an example to explain some of the technical details and characteristics of truck drive motors.
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The rotor section controls heat generation and is also categorized by the number of cylinders.
The stator of the motor
The rotor of a permanent magnet motor may look like a piece of iron at first glance, but it is actually made up of a large number of very thin silicon steel laminations stacked together, with each layer insulated from the others. Thinner silicon steel laminations are better for reducing electromagnetic eddy currents. However, the thinner the laminations, the higher the cost of manufacturing the motor. Manufacturers usually seek a balance between performance and cost.
Stator core
Eddy currents refer to the electromagnetic induction that occurs in conductors exposed to rapidly changing magnetic fields, leading to the heating of metal objects. In everyday life, induction cooktops use this principle to heat metal cookware. By using thin steel laminations and insulating them from each other, the intensity of eddy currents can be significantly reduced, minimizing unnecessary energy loss.
The entire rotor is composed of a combination of six sets of silicon steel laminations. When assembling the rotor, Fast Sunzon intentionally offsets these six sets of iron cores by a certain angle. You can think of it like a six-cylinder engine where each pair of cylinders works together, providing smoother power output compared to all six cylinders operating simultaneously. By employing this technique, the motor achieves smoother power output and reduced noise.
Single-piece neodymium-iron-boron
Stator core embedded with neodymium-iron-boron
The reason a permanent magnet motor is called “permanent magnet” is that the rotor’s magnetism is permanent. The source of the magnetic field comes from these thin neodymium-iron-boron plates. Each phase of the rotor core has four deep slots for inserting the magnetic plates. Once the core is fully filled with these plates, it becomes completely magnetized.
It’s worth mentioning that neodymium-iron-boron (NdFeB) itself is also a conductor and generates heat due to eddy currents when operating within rapidly changing magnetic fields at high speeds. To mitigate the adverse effects of this situation, the magnets inside the magnetic plates are divided into multiple sections, allowing them to conduct the magnetic field while maintaining insulation between each other. With this technique, the operating temperature of NdFeB magnets can be reduced by approximately 30-50 degrees Celsius.
This is crucial because NdFeB magnets are highly sensitive to high temperatures; if the temperature rises to 180 degrees Celsius, they can permanently demagnetize, leading to motor failure.
Stator insulation comes first.
When you see the stator of a flat-wire motor, your first impression might be that it looks really attractive, especially at the end positions, giving it an industrial aesthetic. Why must the wires at the end be twisted instead of being directly connected? The answer is that they cannot be connected directly. The twisting of the wires at a certain angle is not for aesthetic purposes but to align the ends of the wires with another set that needs to be connected and soldered together.
Twisting may seem simple, but it is actually quite complex and requires specialized equipment. It is crucial to ensure that the insulating varnish on the twisted section is not damaged to maintain insulation. Therefore, the insulation varnish on the surface of the motor’s flat wires must have excellent flexibility and uniformity, with no “ulcers” or defects. Additionally, it needs to be resistant to oil and high temperatures to ensure proper operation within a temperature range below 180 degrees Celsius.
Bearing section: Preventing electrical interference
The bearings in a motor may seem like a simple mechanical component, but in reality, they are also influenced by the magnetic field during operation, which can generate electrical currents. These currents can cause sparks inside the high-speed rotating bearings, potentially damaging the working surfaces and contaminating the lubricant. Therefore, when designing and manufacturing a motor, manufacturers need to account for this significant drawback. After all, bearing damage represents a severe mechanical failure for the motor.
While a motor may appear to have a much simpler structure and principle compared to traditional engines, many seemingly simple details actually impact its performance and lifespan. Simplicity does not equate to being rudimentary; achieving peak performance in vehicle motors requires extracting advantages from the details. In the future, trucks will increasingly shift to electric drive, making motors more common. Gaining knowledge about motors in advance will be highly beneficial for future vehicle selection and usage.