Working principle of DC fan:
According to Ampere's right-hand rule, when current flows through a conductor, a magnetic field will be generated around it. If this conductor is placed in another fixed magnetic field, it will generate attraction or repulsion, causing the object to move. Inside the blade of the DC fan, a rubber magnet that is pre-charged with magnetism is attached. Surrounding the silicon steel sheet, two sets of coils are wound around the axis, and a Hall sensor component is used as a synchronous detection device to control a set of circuits that make the two sets of coils wrapped around the axis work in turn. The silicon steel sheet produces different magnetic poles, which produce attraction and repulsion with the rubber magnet. When the attraction and repulsion is greater than the static friction of the fan, the fan blade rotates naturally. Since the Hall sensor component provides a synchronization signal, the fan blade can continue to operate. As for its direction of operation, it can be determined according to Fleming's right-hand rule.
Working principle of AC fan:
The difference between AC fan and DC fan. The former uses AC power supply, and the power supply voltage will alternate between positive and negative. Unlike the DC fan, the power supply voltage is fixed, and it must rely on circuit control to make the two sets of coils work in turn to generate different magnetic fields. Since the power frequency of AC fans is fixed, the speed of magnetic pole change generated by silicon steel sheets is determined by the power frequency. The higher the frequency, the faster the magnetic field switching speed, and theoretically the faster the speed will be, just like the principle that the more poles a DC fan has, the faster the speed will be. However, the frequency cannot be too fast, otherwise it will cause difficulty in activation.
4. About noise:
The noise of the fan is measured in an anechoic room with a background noise of less than 15 dBA. The fan to be tested is running in free air, and a noise meter is placed one meter away from the air inlet.
The noise value of the fan is usually plotted in multiple frequency bands of sound pressure level (SPL). The effect of the change in decibel (dBA) is shown by the following signs:
A> 3 dBA Almost unnoticeable
B> 5 dBA Felt
C> 10 dBA Felt twice as loud
Noise level:
A> 0 ~ 20 dBA Very weak
B> 20 ~ 40 dBA Weak
C> 40 ~ 60 dBA Moderate
D> 60 ~ 80 dBA Loud
E> 80 ~ 100 dBA Very loud
F> 100 ~ 140 dBA Deafening
V. About air volume:
Air volume unit (click: Air volume and air pressure automatic conversion table)
CFS: Cubic Feet Per Second, cubic feet per second (ft3/s)
CFM: Cubic Feet Per Minute, cubic feet per minute (ft3/min)
CMS: Cubic Meter Per Second, cubic meter per second (m3/s)
CMM: Cubic Meter Per Minute, cubic meter per minute (m3/min)
CMH: Cubic Meter Peter Hour, cubic meter per hour (m3/h)
L/s: Liter Per Second, liter per second (L/s)
L/min: Liter Per Second, liter per minute (L/min)
VI. About static pressure:
Static pressure unit
N: Newton, 1n=0.101097Kgf
Pa: Pascal, Pa=N/m^2
mmAq: Aq=Aqua (water column), mmAq is also called mmH2O; 1mmAq=1Kg/m^2
atm: atmospheric pressure; one atmosphere is equal to a pressure of 760mmHg in a dry state at 0℃.
Since the weight of mercury is 13.5947 times that of water, one atmosphere is equal to the pressure of 10332mmH2O
bar: 1 bar=0.00001Pa=10-5Pa
Air volume
The air flow rate sucked in per unit time by the blower is called air volume (Air volume, Air quantity), usually Q (m*3/min) is the gas volume. When sucking air, it is called air volume, and in the case of fans, it is also called air volume. (Capacity) Gas changes its volume according to its pressure and temperature, so when mentioning the amount of air discharged, it is necessary to note the pressure and temperature of the place, so it is called the amount of air sucked.
* Standard state air:
The standard air is humid air with a temperature of 20°C, an atmospheric pressure of 760mmHg, and a humidity of 65%. The weight of air per unit volume (also known as specific weight) is L2Kg/m*3
* Reference state air:
The standard air is humid air with a temperature of 0°C, an atmospheric pressure of 760mmHg, and a humidity of 0%. The weight of air per unit volume (also known as specific weight) is 1.293Kg/m*3. Expressed in Nm*3/min
