[Table fan circuit diagram] The structure of the table fan is the introduction of the speed control method of the table fan
The table fan, including the base, the fan blade, the fan cover and the rear shell, all The upper part of the rear casing is provided with a handle; because the handle is arranged on the rear casing, the structure is more reasonable, the force of the table fan is more uniform when carrying it, which is convenient for the user to move and carry the table fan, and directly set The handle on the rear shell is firm and durable, and is more suitable for moving and carrying heavier desk fans. widely used.
Structural composition of desk fan
(1) Fan blades. The number of blades, torsion angle, cross-sectional shape and material selection all have a significant impact on the wind pressure, wind maximum, noise and input power of the fan. Fan blades are generally made of 1-1.5 mm aluminum plate or ABS plastic, and can only be used after strict calibration and balance.
(2) The grille. It can prevent the human body from touching the fan blades.
(3) Motors. There are two types of capacitor type and shaded pole type, 300 ~ 400 mm specification table fan with capacitor. There are many types, 200 ~ 250 mm specifications table fan capacitive type, cover plate type.
(4) Shaking mechanism. The shaking of the table fan is driven by the motor of the table fan, and then realized by the transmission of various components. Generally, after the secondary deceleration, the motor is reduced from about 1400 revolutions per minute to the swing of the fan head part 4 to 6 times per minute. The maximum swing angle varies depending on the specifications of the table fan.
(5) Pedestal. The base requires good stability. Equipped with speed control switch, shaking head control switch, timing switch and indicator light, etc. Reactors and timers are all customized on the panel.
Speed regulation method
The speed regulation of the electric fan table fan is realized by reducing the winding voltage, weakening the magnetic field strength, and changing the rotational speed. There are reactor speed regulation, tap speed regulation, thyristor speed regulation, capacitor speed regulation and other methods for the speed regulation of AC 220V table fans. At present, the first two methods are mainly used.
(1) Reactor speed regulation method. The reactor speed regulation is to reduce the number of merits per turn by reducing the applied voltage of the fan motor to achieve the effect of weakening the magnetic field strength. The reactor speed regulation circuit is shown in Figure 1. The advantages of this method are that it is easy to adjust the speed regulation ratio of each gear, the maintenance is convenient when the winding is short-circuited between turns, and the winding is simple and does not require taps. The disadvantage is that the speed regulation is often affected by the external power supply voltage, especially the slow start is the most obvious.
(2) Tap speed regulation method. The tap speed regulation method is to change the volts per turn of the winding, that is, to change the number of turns of the auxiliary winding to weaken the magnetic field strength to achieve the purpose of speed regulation. The advantage of this method is that the speed regulation is relatively simple, no external reactor is required, which can save man-hours, materials, and reduce costs. Therefore, the tap method is used for speed regulation of capacitive table fans at home and abroad. The disadvantage is that winding, embedding, wiring, etc. are more complicated.
The motor with tap speed regulation has three coils: the main winding, the middle winding and the auxiliary winding. According to the different wiring positions of the middle winding, it is divided into three types of tap speed regulation circuits: L-shape, T-shape and K-shape.
(3) SCR speed regulation method. It is a stepless speed regulation method, which is not widely used because the use of thyristor speed regulation needs to overcome the problem of large electromagnetic noise.
(4) Capacitor adjustment is illegal. The use of capacitors instead of reactors for speed regulation can save electricity and reduce volume. This method may become the main method for speed regulation of electric fans.
(5) Speed regulation of the windshield. In recent years, in order to increase the breeze function of electric fans, PTC devices are used as the breeze speed.
This is designed to be able to sleep with an electric fan on in summer. Generally speaking, the highest speed of the fan is about 1400 rpm, and the speed regulation ratio is 0.7 to 0.8, that is, the lowest speed is 1400 rpm. 1000 to 1100 revolutions per minute, which is not good for the health of those who fall asleep. If the original method is used to further reduce the speed, the process is complicated, the cost increases, and the starting performance is difficult to guarantee. Using positive temperature coefficient thermal resistance PTC device speed regulation. The speed of the motor can be reduced to about 500 revolutions per minute, and it can be started smoothly. It is realized by connecting a PTC device in series in the original slowest line.
