1. General knowledge of cooling fans:
In general, the following necessary information should be understood when choosing a fan:
The size of air blower.
To determine whether the fan is dc or ac.
The power supply voltage of an air blower.For example: communication 220V, 110V, 380V.Dc 5V, 12V, 24V, 36V, 48V.
Air blower bearings, ball bearings or oil.
Air volume, speed of air blower.For example, how many cubic meters per minute, or how many cubic feet per minute.
Air pressure value.
2. Bearing:
Oil Bearing
Traditional brushless dc fan motor carbon brush design, is the blade rotor (rotor) and the shaft core through the oil-retaining bearing, referred to as "SLEEVE bearing, fixed pin joint in the center position of the motor stator, rotor and the stator maintain an appropriate gap between core shaft and bearing, of course, also be sure to have a gap between the existence of, don't lock shaft core die not;The stator structure part of the motor (the stator for short), after the power input, will generate the induction magnetic force line between the rotor and the stator, and the control of the drive circuit will make the fan motor run.Therefore, the traditional fan motor structure has only one fan blade rotor, one motor stator and one driving circuit, which is connected with the pivot of the bearing by the shaft core and operates with magnetic induction.
1.Use the advantages of oil bearing
A.Less damage during transportation due to shock resistance;
B.Low price (price difference is very large compared to ball bearing.
2.Disadvantages of using oil bearing
A.Dust in the air is drawn into the core of the fan motor and mixed with the lubricating oil stored around the bearing to form mud, which makes the running noise, or even stuck.
B.The inner diameter of the bearing is easy to wear away and the service life is short.
C.Cannot be used on portable products;
D.The clearance between the bearing and the shaft core is small, and the motor operation and activation effect is poor.
E.The high-temperature gas generated by friction between the motor's rotating shaft and the bearing can't be eliminated due to the obstruction of oil ring and husi at both ends of the bearing, forming nitride compounds, which can easily obstruct the clearance between the shaft and the bearing and hinder the smooth operation of the motor.
Ball Bearing
Ball bearings are operated by round metal beads, which belong to point contact, so it is easy to activate the operation.Combined with ball bearings used with spring, so at the top of the spring with a BALLBearing metal ring, and the whole weight of the rotor blades is located on the ball bearing, and by spring indirect top bracing, so it can be used in different direction, Angle of portable products, but still to prevent falling, in order to avoid the ball bearing is damaged, and cause the noise generation and the service life of the impairment.
1.Advantages of using ball bearings
A.The movement of metal bead belongs to point contact, so it is easy to activate the movement.
B.It can be used in portable products which are usually operated at different angles and directions (but should be prevented from falling or falling);
C.Long service life (compared with oil bearing).
2.Disadvantages of using ball bearings
A.The bearing structure is too fragile to bear the impact of external forces.
B.When the motor rotates, the rolling of the metal beads will produce greater noise.
C.High price, unable to compete with oil bearing in cost price;
D.The source and quantity demand of ball bearing are difficult to control.
E.Ball bearing USES the spring's elasticity and makes its localization, on the assembly is relatively difficult.
Iii. Working principle of fan
Working principle of dc fan:
According to the right hand rule of ampere, a conductor passing through an electric current will generate a magnetic field around it. If this conductor is placed in another fixed magnetic field, it will generate suction or repulsion, causing the object to move.Inside the fan blade of a dc fan, a rubber magnet is attached.Surrounding the silicon steel sheet, the shaft part is wrapped around two sets of coils, and the hall induction module is used as synchronous detection device to control a set of circuits, which makes the two sets of coils of the axis rotate.The silicon steel sheet produces a different magnetic pole which produces a repulsive force with the rubber magnet.When the repulsion force is greater than the static friction force of the louse fan, the blade rotates naturally.Since the hall sensor provides a synchronous signal, the fan blade can continue to operate. The direction of its movement can be determined according to the right hand rule of Fleming.
Working principle of ac fan:
The difference between an AC fan and a DC fan.The former power supply is ac, the power supply voltage will be positive and negative alternating, unlike the DC fan power supply voltage is fixed, which must be controlled by the circuit, so that the two groups of coils can work to generate different magnetic fields.Since the frequency of AC fan is fixed, the change speed of magnetic pole generated by silicon steel sheet is determined by the frequency of power supply. The higher the frequency, the faster the switching speed of magnetic field will be, in theory, the faster the speed will be, just like the principle that the more the number of dc fan poles, the faster the speed will be.However, the frequency cannot be too fast, and too fast will make activation difficult.
Iv. About noise:
The fan noise is measured in the background noise less than 15 dBA echo chamber.The fan under test runs in free air, one meter from the inlet vent to dispose of a noise meter.
The noise value of the fan is usually plotted on a frequency band of sound pressure level (SPL).The effect of the change in db (dBA) is shown by the following symptoms:
A> 3 dBA barely felt
B, >, 5 dBA
C b b 0 10 dBA feels twice as loud
Noise level:
A> 0 ~ 20 dBA is weak
B> 20 ~ 40 dBA weak
C b b 0 40 ~ 60 dBA moderate
D b b 0 60 ~ 80 dBA loudly
E b b 0 80 ~ 100 dBA very loud
F b 0 100 ~ 140 dBA is deafening
V. 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/Minute (ft3/min)
CMS: Cubic Meter Per Second, Cubic Meter Per Second (m3/s)
CMM: Cubic Meter Per Minute, Cubic Meter /min (m3/min)
CMH: Cubic Meter Peter Hour, Cubic Meter/Hour (m3/h)
L/s: L/s, L/s.
L/min: L/min
Vi. Static pressure:
Static pressure units
N: Newton, 1n=0.101097Kgf
Pa: Pascal, Pa = N/m ^ 2
MmAq: Aq=Aqua(water column) abbreviation, mmAq is also known as mmH2O.1 mmaq = 1 kg/m ^ 2
ATM: atmospheric pressure;A is equal to atmospheric pressure at 0 ℃ 760 MMHG pressure drying condition.
Since mercury weighs 13.5947 times as much as water, one atmosphere is equal to 103,32mmh2o
Bar: 1 bar = 5 Pa Pa = 10-0.00001
The air volume
Air volume (Air quantity) is the Air flow absorbed by the fan per unit of time. Usually, Q(m*3/min) is the Air quantity when the Air is inhaled.(Capacity) the volume of a gas changes according to its pressure and temperature. Therefore, when referring to the amount of air discharged, the pressure and temperature of the place must be noted.
* standard air:
20 ° C temperature, atmospheric pressure, 760 MMHG, moist air humidity of 65% for the standard air, this time the weight of per unit volume of air (also called than weight) for L2Kg/m * 3
* baseline air:
0 ° C temperature, atmospheric pressure, 760 MMHG, moist air humidity of 0% for the standard air, this time the weight of per unit volume of air (than) weight of 1.293 Kg/m * 3.In order to * 3 Nm/min said
IP level:
IP grade is a set of physical standards defined at IEC60529 (bvsen60529:1991).The IP level is expressed as two Numbers (example: IP55).The first number defines the level of protection for contact and particles, and the second number defines the level of protection for water.
* insulation level:
The maximum permissible operating temperature for the insulation system is estimated by the standard National Electrical Manufacturers Association (aea) as follows:
• T(oF) = [T(oC)](9/5) + 32
The allowable temperature rise is based on the base ambient temperature of 40oC. The operating temperature is the base ambient temperature + allowable temperature rise + coil tolerance "hot spot".
The following example is temperature tolerance level F: 40oC + 105oC + 10oC = 155oC.
General motor operating temperature should not be used above the maximum value, each increase of 10oC May reduce the motor life by half.
Temperature tolerance grade B is commonly used for 60 Hertz and American motors.Temperature tolerance grade F is commonly used in international and 50 Hertz motors
