The Influence of Motor Magnetic Stripes on the Performance of Cooling Fans
Categories:
Technology
Author:
rain
Origin:
capital
Time of issue:
2025-06-17 09:16:54.000
Views:
Motor magnetic strip (usually referring to the permanent magnet in the motor, such as the permanent magnet in brushless DC motor BLDC) is one of the core components of the cooling fan, and its performance directly affects the fan's speed, air volume, noise, efficiency, and reliability.
The following analyzes the impact of magnetic stripes on the performance of cooling fans from multiple dimensions:
一、The influence of magnet materials
- Common types of magnets
Neodymium iron boron (NdFeB):
Advantages: High remanence density (Br) and coercivity (Hc), strong magnetism, can drive fans to achieve high speed, large air volume, and high static pressure, suitable for scenarios that require strong heat dissipation capabilities (such as servers and high-performance CPU heat dissipation).
Disadvantages: High cost, easy demagnetization at high temperatures (attention should be paid to temperature resistance levels, such as N35, N52, etc., with a temperature resistance range of usually 80 ℃~220 ℃).
Ferrite:
Advantages: Low cost, good high temperature resistance (up to 200 ℃), and not easily demagnetized.
Disadvantages: Weak magnetic properties result in lower fan speed and air volume, making it suitable for low load, economical scenarios such as regular computer case fans and home appliance cooling.
Samarium cobalt (SmCo):
Advantages: Excellent stability in ultra-high temperature environments (temperature resistance exceeding 300 ℃), corrosion resistance.
Disadvantages: Extremely high cost, only used in extreme scenarios such as aerospace and industrial high temperatures.
- Direct impact on fan performance
Speed and air volume:
The stronger the magnetic properties of the magnet (such as neodymium iron boron), the greater the electromagnetic driving force of the motor, and the fan can achieve higher speeds, thereby increasing the air flow (CFM) and static pressure (mmH ₂ O).
Efficiency and energy consumption:
Strong magnets can reduce motor current losses and improve efficiency (lower power consumption under the same air volume), especially suitable for low-power devices such as laptop fans.
High temperature reliability:
Ferrite is not easy to demagnetize in high temperature environments (such as car engine compartments and industrial ovens), while neodymium iron boron needs to choose a temperature resistant model (such as HT series), otherwise demagnetization may cause a decrease in speed or even stoppage.
Noise and vibration:
The interaction between motor magnetic strips and stator coils is one of the main causes of noise and vibration. If the magnetic stripe design is unreasonable or installed inaccurately, it may cause significant fluctuations in the magnetic field, which in turn can lead to fan vibration and noise.
二、The influence of magnet size and shape
- Magnet thickness and curvature
Thickness:
Increasing the thickness of the magnet can enhance the air gap magnetic field strength and improve electromagnetic force, but it will increase the volume and weight of the motor, which may affect the compactness of the fan (such as balancing the thickness and performance of the magnet for ultra-thin fans).
Radiance:
Curved magnets (instead of rectangles) can optimize magnetic field distribution, reduce cogging torque, lower vibration and noise, and improve motor stability, making them suitable for high noise reduction scenarios such as medical equipment and office environment fans.
- Arrangement method (radial/axial magnetization)
Radial magnetization:
Commonly found in external rotor BLDC motors (mainstream structure of cooling fans), the magnets are arranged radially along the circumference, providing a large torque and suitable for high static pressure requirements (such as wind pressure fans, used in scenarios with dense cooling fins).
Axial magnetization:
Less commonly used for cooling fans, it is more common in special structure motors with different torque characteristics, which may affect the fan's air volume static pressure curve.
三、Temperature and demagnetization risk
After demagnetization, the magnetic strip (permanent magnet) will directly damage the electromagnetic drive foundation of the cooling fan, leading to the deterioration of multiple performance indicators and even causing functional failure.
- The influence of temperature on magnetic properties
The residual magnetic density (Br) of permanent magnets decreases with increasing temperature, and will significantly demagnetize beyond the critical temperature (such as the Curie temperature of neodymium iron boron, which is about 310 ℃~580 ℃).
Ferrite: better temperature resistance than neodymium iron boron, stable performance below 150 ℃, suitable for high temperature environments.
NdFeB: The model should be selected according to the operating temperature (such as N35 with a temperature resistance of 80 ℃, N48H with a temperature resistance of 180 ℃). Exceeding the temperature resistance range can lead to a decrease in speed, efficiency, and even permanent failure.
- The correlation between heat dissipation design
The self heating of the fan (such as copper loss and hysteresis loss in the winding) may exacerbate the temperature rise of the magnet, and it is necessary to optimize the motor structure (such as adding heat sinks, using low loss silicon steel) or choose high-temperature resistant magnets to reduce the demagnetization risk.
Summarize
The motor magnetic strip comprehensively affects the power performance (air volume/static pressure), energy efficiency, noise, and reliability of the cooling fan through dimensions such as material characteristics, size design, temperature tolerance, and processing accuracy.
In the design, it is necessary to balance the performance of the magnet with other motor parameters (such as winding design, bearing type) based on the temperature, load, cost and other requirements of the application scenario, in order to achieve the optimal heat dissipation effect.
Capital Technology Co., Limited is the chief agent of SANYO DENKI, one of the leading enterprises of the cooling fan industry. We are a factory who also have our own independent brand CAPITAL product series. The main products are cooling fan, DC/AC fan, radiator, filter, reactor etc. We can provide customer with the most professional and perfect technical support, welcome to contact me at anytime at rainlee@szcpt.com.
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