Analysis of the Internal Structure of the Cooling Fan

2026-02-06

Understanding Fan Lead Differences

1，Let's easily understand the differences in the functions of the fan leads together!
The two-wire fan is equipped with a pair of power lines (red for positive, black for negative), with a simple structure and suitable for basic cooling scenarios; the three-wire fan adds a yellow speed signal line on this basis, which can provide real-time feedback on the running speed, allowing you to better and more securely monitor the fan status; while the four-wire fan further upgrades by adding a blue PWM speed control line, supporting intelligent and precise speed control - all other leads have the same functions as the three-wire type, ensuring a worry-free upgrade and smooth compatibility.

Next, we will provide a detailed introduction to the internal structure of the Cooling Fan.

First, the plastic snap-on connection that fixes the bearing stator needs to be removed.

After removing the clamping connection, the cooling fan can be divided into two parts: the left part is the rotor component, which includes the fan blades and the ring-shaped permanent magnets distributed around; the right part is the stator component, which is composed of an iron core with enameled wires wound around it. When the stator coil is energized, an alternating magnetic field is generated, which interacts with the magnetic field of the rotor permanent magnets, thereby driving the rotor to rotate and achieving continuous cooling.

After removing the stator coils, the PCBA (printed circuit board assembly) can be observed. Its core functional components mainly consist of two parts: One is the PWM driver chip (model: SL11660F), which is an integrated control solution specifically designed for brushless DC motors (BLDC). This chip integrates functions such as gate drive, current detection, and protection logic.

In contrast, the PCB designs corresponding to two-wire and three-wire fans are significantly simplified: apart from the conventional passive components (such as resistors and capacitors), their core functions are mainly achieved through Hall effect sensors (Hall IC), which are used for rotor position detection and phase control.

Furthermore, two precision ball bearings can be observed. Their highly accurate mechanical structure and excellent load-bearing and wear-resistance properties are the key components that ensure the long-term stable operation and high reliability lifespan of the fan. Besides the ball bearings, heat dissipation fans also often adopt different technical routes such as oil-filled bearings (Sleeve Bearing) and fluid dynamic bearings (Fluid Dynamic Bearing, FDB). There are significant differences in lifespan, noise, start-stop characteristics and cost among various bearings. The specific comparison is shown in the following figure.

In addition to the aforementioned basic structural components, the selection of the cooling fan also needs to comprehensively consider key performance parameters such as rated operating voltage, air volume (CFM), sound pressure level (dBA), static pressure, protection level (IP rating), and environmental adaptability to match the technical requirements of specific application scenarios. Although the appearance structure is simple, its design and application involve multiple disciplines such as fluid mechanics, electromagnetic drive, thermal management, and reliability engineering.

If you have customized requirements in the field of cooling fans, please feel free to contact Shenzhen Fuqingda Electronic Tech Co., Ltd. - We have over 20 years of professional manufacturing experience and can provide full-cycle technical services covering OEM, ODM, and joint development to help customers efficiently solve thermal management challenges.