DC blowers have been the go-to solution for air distribution for many years, providing efficient cooling from a few watts to hundreds of watts for products that require heat dissipation or providing the right airflow for occasions that require it. To ensure proper fan selection, it is important to align the cooling needs of the system with the fan's airflow characteristics.
This article will provide a detailed DC blower purchase guide.
What is a DC blower?
DC blower, as the name suggests, is a heat dissipation blower that converts electrical energy into electromagnetic energy through DC voltage and electromagnetic induction, then into mechanical energy, and finally into kinetic energy, so that the fan blades rotate.
The traditional DC blower is mainly composed of rotor, stator, motor and frame. The DC motor consists of a permanent magnet rotor, a multi-level winding stator, a position sensor and an electronic commutation drive control circuit.
The rotor is composed of: motor casing + permanent magnet strip + shaft core + fan blade.
The stator is composed of: enameled wire + plastic-coated silicon steel sheet + bearing + Hall sensor detection + drive circuit board + rotating shaft.
Working principle of DC blower
The core components of the DC blower are the stator and the rotor. According to Ampere's right-hand rule, we know that when current passes through a conductor, a magnetic field is generated around it. If the conductor is placed in another fixed magnetic field, an attraction or repulsion will be generated, causing the object to move. The blades of DC blowers are filled with magnetic rubber magnets inside. Around the silicon steel sheet, two sets of coils are wound on the shaft respectively, and the Hall sensor module is used as a synchronous detection device to control a set of circuits. The circuit makes the two sets of coils around the shaft work alternately, so that the silicon steel sheet produces different magnetic poles, and produces attractive and repulsive forces with the rubber magnet.
Due to the synchronous signal provided by the Hall sensing module, the blower blades can rotate continuously, and the direction of rotation can be determined according to Fleming's right-hand rule.
The difference between DC blower and AC blower
Cooling blowers mainly include DC cooling blowers and AC cooling blowers. The difference between the two blowers is mainly reflected in the following three points:
1. Different principles
The power supply of the AC cooling blower is alternating current, and the power supply voltage will change sinusoidally. However, the voltage of the power supply is fixed and must be controlled by the circuit so that the two sets of coils work in turn to generate different magnetic fields. Since the power frequency of the AC blower is fixed, the speed of the magnetic pole change generated by the silicon steel sheet is determined by the power frequency. The higher the frequency, the faster the magnetic field switches. Theoretically speaking, the speed will be faster, just like the principle that the more poles of a DC blower, the faster the speed. But the frequency should not be too fast, otherwise it will cause difficulty in activation. We use DC blowers on our computer coolers. Generally speaking, a good cooling blower mainly depends on the air volume, speed, noise, service life and the type of blade bearings.
2. Different airflow
For heat dissipation blowers of the same size and specification, AC blowers have large motors and short blades, while DC blowers are just the opposite, with long blades and small motors, such as miniature DC blowers, so the more air volume per unit area, the greater the air volume, the better the cooling capacity .
3. Different materials
The outer frame of the AC blower is generally an aluminum frame, while the outer frame of the DC blower is a plastic frame. Therefore, the temperature resistance ability is different. The choice of DC blower or AC blower depends on which product is more suitable for your product at the same cost
How to choose the right DC blower
When designing electrical and electronic equipment, engineers need to determine the airflow required to dissipate heat. To prevent overheating, the required air flow value depends on the power dissipation in the system to ensure sufficient heat removal. Facts have shown that the service life of the system will decrease due to insufficient cooling system, and the sales volume and price may decrease because the service life does not meet the user's expectations.
To select an appropriate heat sink, the following objectives must be considered:
- Efficient airflow
- Minimum size and fit
- Minimum noise
- Lowest power consumption
- Reliable and long service life
- Reasonable cost
Below are three basic steps in selecting the proper blower or blower for your application to achieve the above goals.
Step 1. Overall Cooling Requirements
The first step is to identify three key factors to obtain the total cooling requirements:
- Heat that must be transferred: Difference in temperature (DT)
- Electrical Power to Counteract Transferred Heat (W)
- Airflow Required for Cooling (CFM)
The overall cooling requirements are very important for the system to operate efficiently. An efficient operating system is about providing the required operating conditions for all components in the system to maximize performance and longevity.
The following methods can be used to select the fan motor:
- Determining the amount of heat generated inside the device
- Determine the allowable temperature rise range inside the device.
- Calculate the required air volume according to the formula.
- Estimate the system impedance of the device.
- Select the blower according to the performance curve shown in the catalog or data sheet.
- If the internal heat dissipation and the allowable total temperature rise are known, the air volume required to cool the equipment can be obtained.
The basic heat transfer equation is as follows:
H = Cp × W × T
H = heat transferred
CP = specific heat of air
Δt = temperature rise inside the cabinet
W = mass flow rate
We have W = CFM × D, where D = air density.
After substitution, we get
Q (cubic feet per minute) = Q / ( Cp * D * ΔT )
Combining the conversion factor with the specific heat and density of air at sea level yields the following heat dissipation equation: CFM = 3160 × KW / △℉
Then the following equation is obtained:
Q (cubic feet) = 3.16 * P / ΔTf = 1.76 * P / ΔTc
Q (M3/minute) = 0.09 * P / ΔTf = 0.056 * P / ΔTc
Q: Airflow required for cooling
P: The heat dissipation inside the cabinet (that is, the electrical power consumed by the equipment)
TF: Allowable internal temperature rise in degrees Fahrenheit
TC: Allowable internal temperature rise in degrees Celsius
DT = temperature difference between DT1 and DT2
Step 2: Total System Impedance/System Characteristic Curve
When the air flows, it will encounter the obstruction of the internal parts of the cabinet on its flow path, and the impedance will restrict the free flow of air. Pressure change is static pressure in inches of water.
In order to determine the cooling power of each slot, the system designer or manufacturer must not only have the characteristic curve of the blower to determine the maximum air volume, but also must know the wind resistance curve of the system. There is a loss of air pressure due to the resistance of the components inside the cabinet. This loss varies with airflow and is called system resistance.
The system characteristic curve is defined as follows:
DP = KQn
K = system characteristic coefficient
Q = air flow (cubic feet)
N = interference factor, 1 < n < 2
For stratospheric flows, n = 1
In turbulent flow, n = 2
Step 3: System operating point
The intersection of the system impedance curve and the airflow characteristic curve is called the system operating point and it is the optimum operating point for the blower for your application.
At the operating point, the change slope of the fan characteristic curve is the smallest, while the change rate of the system characteristic curve is the lowest.
Note that the static efficiency of the blower (air flow times static pressure divided by power consumption) is also optimized.
Design Considerations:
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Try to keep the airflow channel unobstructed, and keep the air inlet and outlet unimpeded so that the airflow can circulate.
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Direct airflow through the system vertically to ensure smooth airflow and improve cooling efficiency.
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If an air filter is required, additional resistance to air flow should be considered
Conclusion
It is very important to choose the right blower for your application, he determines whether your application can run flawlessly.
You can communicate with our engineers, or view our products. If you have any needs, you can contact us immediately.
