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[Fan types and features] Cooling fans
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When we think of fans, many people probably think of electric fans or ventilation fans used in the home, but the "cooling fans" introduced here are fans that are installed inside equipment to cool the equipment. In recent years, cooling fans are increasingly being used for purposes other than cooling, such as ventilation and air circulation.
Fan types are often categorized by input power source and fan shape.
There are two types of input power: alternating current (AC) and direct current (DC), and they are generally called AC Cooling Fan and DC Cooling Fan. Fans can be broadly divided into three types based on their shape: axial fans, Centrifugal Fan, and blowers.
When searching for a product, if you come across a product name like "DC axial fan", you know that it is an axial fan with a DC input power supply. Of course, different manufacturers may call them differently, but there is no big difference in how they are classified.
Related article: Knowledge "2nd Period: Types of Fans"
Figure 1: Cross-section of a fan
Let's explain using a cross-section diagram of a fan.
A cooling fan is basically made up of the parts shown in Figure 1, but the most important of these is the "ball bearing."
SANYO DENKI CO., LTD. uses a dual ball bearing structure for all of its models, which reduces the bearing load and improves the reliability and lifespan of the fan.
Figure 1: Cross-section of a fan
Related article: Knowledge "3rd Lesson: Fan Lifespan"
If you want to control the rotation speed of a fan, you can use the PWM control function PWM control function, which controls the rotation speed by changing the pulse width of the control signal, allowing for a wider range of control than when controlling by voltage.
To use PWM control function, a circuit that generates a PWM signal is required. If it is difficult to build your own circuit, SANYO DENKI CO., LTD. 's "PWM Controller" allows you to use PWM fan without designing a circuit. We also offer the IoT product "San Ace Controller" that can remotely monitor and control the rotation speed of a fan.
If a fan makes noise when installed in a device, it may be that the fan is hitting the device as it rotates. One way to deal with this is to use anti-vibration rubber to absorb the vibration. Another possibility is that the device is resonating with the fan. In this case, you need to increase the rigidity of the device to prevent the fan rotation speed from resonating with the device.
Figure 2: Example of ventilation resistance and air volume - static pressure characteristics
On the other hand, there are three main factors that cause noise to come from the fan itself.
Wind noise: The sound made by blades cutting through the air as they rotate.
Electromagnetic noise: Mainly motor switching noise, etc.
Mechanical noise: Vibration noise caused by imbalance in the rotating body (rotor).
These are determined during the fan manufacturing process, but "wind noise" can be reduced by adjusting the rotation speed using PWM control function, etc. Because the sound pressure level of a fan changes depending on its rotation speed, it is fine to set the rotation speed at which the noise is lowest, but this will also change the airflow, making it difficult to balance this with cooling performance.
Therefore, if you want to reduce noise while maintaining optimal cooling performance, it is best to consider the optimal operating point when selecting a fan, taking into account the ventilation resistance of the device and the fan's airflow-static pressure characteristics.
Figure 2: Example of ventilation resistance and air volume - static pressure characteristics
Related article: Knowledge "7th lesson: Ventilation resistance of equipment"
What is the method for quantifying airflow when a fan is installed in a device?
What is an "ACDC Fan" that achieves the performance of DC Cooling Fan with AC power?
What is a "Centrifugal Fan" that reduces the number of fans while improving cooling performance?
High static pressure "Oil Proof Fan" ensures cooling performance even in harsh factory environments
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