We now deal in three types of fans: desk fans, ceiling fans and exhaust fans.

Types and structures of electric fans

The electric fan drives the blades to rotate at high speed through the motor, which forces the air to move faster and improves the heat exchange between the human body and the surrounding air, thus taking away more heat from the human body and making people feel cool.

There are many kinds of electric fans, according to the nature of power supply, including AC, DC and AC -DC dual-purpose electric fans; According to the mode of use, there are desk fans, ceiling fans, exhaust fans and air coolers.

The size specification of electric fan usually refers to the size of fan blade, which is either metric or English, and the comparison table between metric and English is used.

(1) desktop fan

The desktop fan is composed of fan blades, a net cover, upright posts, a base, an electric control, a fan head motor, a shaking mechanism and a connector. Among them, the motor, fan blades and shaking mechanism are the main components of the desk fan, and they are also the key to determine the performance and quality of the desk fan.

1, motor

There are two kinds of motors used in electric fans: shaded pole type and capacitor operation type.

(1) Covered-pole motor: Most of the electric fans produced in the early days used covered-pole motors, which are small in size and simple to manufacture, and do not need capacitors and starting devices, but have low power and poor performance. So it is seldom used now.

(2) Capacitor-operated motors, which are widely used now, are mainly composed of front end cover, rear end cover, stator rotor and so on.

Stator includes stator core and stator winding. Because the electric fan does not need forward and reverse rotation, the design of the stator main winding and auxiliary winding is different. The secondary winding has more turns and smaller wire diameter than the primary winding.

The rotor includes a rotor core, a rotor winding and a rotating shaft. One end of the rotating shaft is provided with a fan blade; At the other end, the worm engages with the worm wheel in the rocking gear box to realize the rocking motion.

The main function of the capacitor connected in series with the secondary winding is to divide the single-phase alternating current into two phases. Thereby generating a two-phase rotating magnetic field; The rotor is rotating, so the capacitor-operated motor is superior to the shaded pole motor in starting performance, efficiency, power factor and low noise.

2. Rocking mechanism

The rocking mechanism of desktop fan consists of two-stage reducer, connecting rod mechanism, control mechanism and overload protection device. The knob of that shake mechanism is connected with the shake mechanism through a steel wire rope. There are lever clutch mechanism, screw mechanism and skateboard mechanism. Usually we use lever clutch.

Its working process: after electrifying, the worm at the rear end of the motor shaft rotates. Because the worm is engaged with the worm wheel, the worm rotates to drive the worm wheel to rotate, and the worm wheel rotates to drive the lower gear of the clutch to rotate through the overload protection device (primary deceleration).

When the knob is turned to the shaking position, the steel wire rope is in a relaxed state, the upper teeth of the clutch are pressed downwards under the action of the compression spring and meshed with the lower teeth of the clutch, the transverse grooves on the upper teeth of the clutch are meshed with the transverse pins on the meshing shaft, so that the meshing shaft rotates together, and the spur gear at the lower end of the meshing shaft is meshed with the rocking spur gear (secondary deceleration). The straight tooth rotation of shaking head drives the swinging connecting rod and the swinging plate to move, so that the fan head swings back and forth. After two decelerations, the motor rotates from 14 10 to 5-6 revolutions per minute. When the control knob is turned to the position where it does not shake its head, the wire rope is in a tight state, the upper and lower teeth of the clutch mechanism device are separated, and the fan head stops rotating.

The present desk fans have been greatly improved in appearance, all of which are quite small and unique, and many new functions have been added in control. For example, switches are no longer a unified key type. Now there are touch, computer control and remote control. Judging from the form of blowing, it is no longer the third gear. Now, the function of simulating natural wind and interval stop operation has been added. The so-called simulation of natural wind means that when the motor of the electric fan rotates, it is fast and slow, which makes people feel the change of wind speed, thus playing the role of simulating natural wind. Intermittent stall means that the motor rotates for 5 minutes and stops 1 minute, and then rotates and stops again and again.

(2) ceiling fan

The ceiling fan has the characteristics of uniform and soft air volume. The ceiling fan consists of fan blades, fan heads, suspenders and hangers, an upper cover and a lower cover, and a separately installed governor.

Derrick and climbing slope are the parts that hang the fan head and blades, and they are acted by two forces during the working process: one is tension and the other is torque. For the sake of safety, the suspenders and hangers should be able to withstand the pulling force of 100 kg and the torque of 500 kg/cm. The suspender is made of seamless steel pipe, and the motor power cord passes through the pipe.

The fan head consists of motor, upper cover and lower cover. Ceiling fan motor is different from table fan motor, table fan adopts protective type, while ceiling fan adopts closed outer rotor structure. The advantages of this structure are: the stator is in the middle of the motor, and the spindle connected to it does not rotate; The outer rotor can be placed around the stator to drive the fan head shell fixedly connected with it to rotate together, and the fan blades installed on the fan head shell also rotate and tighten at the same time. The rotating speed of ceiling fan is generally 200-300 rpm.

Now, in addition to traditional ceiling fans, there are more decorative and practical fancy ceiling fans. Their shells are no longer traditional white, and their blades are no longer limited to three pieces. Now the colors are bronze and golden yellow, with four leaves, some of them are wood, and the flowers are engraved on them, which looks more chic. Functionally, it can be blown downward or upward in the opposite direction, so that the air circulates, and some increase the lighting. Three or more lamp holders are installed below the fan and covered with fancy lampshades to form a multifunctional fan integrating lighting and blowing. In terms of speed regulation, the wall-mounted governor is not used, but the governor is installed on the fan head in the form of cable, which has an antique taste.

(3) Exhaust fans: At present, there are many brands of exhaust fans, including Masano, Panasonic, Green Island Wind, Mitsubishi, Kate and Ji Hu. There are two installation methods, louver type and ceiling type. Venetian refers to the installation on the steel window wall, and suspended ceiling is installed on the top (ceiling). There are two kinds of ceiling exhaust, direct exhaust and pipeline exhaust. There are two ventilation modes: one-way ventilation and two-way ventilation. One-way ventilation is only exhausting without blowing, and two-way ventilation is exhausting without blowing. In the purchase of ventilation fans, you can equip them with different ventilation times according to the area of your room. Generally, a 4-square-meter room equipped with 1.5-2 m2 ventilation can meet the demand. In addition, products with low input power and low ventilation noise should be selected.

Speed regulation of electric fan

Speed regulation function is one of the basic requirements for electric fans now. The speed regulation mode of electric fan depends on the motor it uses. The electric fans of single-phase capacitor motors and shaded pole motors adopt reactance method, tap method and electronic method for speed regulation.

1, reactor speed adjustment method

The speed regulation of the reactor is realized by reducing the applied voltage of the motor. Its characteristics are easy speed regulation, simple winding and convenient maintenance. The disadvantage is that it cannot be adjusted at will.

2, tap speed regulation method

Tap speed regulation method is realized by changing stator winding. Its characteristics are less power consumption, less materials and light weight, but its winding, embedding and wiring are complicated, and its application scope is limited to some extent.

There are three kinds of coils in tapped speed regulating motor: primary winding, intermediate winding and secondary winding. According to the wiring position of the intermediate winding, it can be divided into L-type, T-type and H-type. L type is divided into L 1 and L2. L 1 The middle winding and the main winding are embedded in the same slot, and the two windings are in the same phase, which is suitable for motors with power supply voltage of 1 10V. L2 middle winding and secondary winding are embedded in the same slot, and the two windings are in the same phase, which is suitable for 220V capacitive motor. The middle winding of T-shaped wiring is connected to the connection point of the main and secondary windings, and the middle winding and the main winding are embedded in the same slot and in the same phase. H- connection taps directly from the middle of the main winding, and then connects the capacitor and the secondary winding. This method is superior to L-type. In the middle, high and low gear, the upper half current phase or the lower half current phase of the main winding of the motor is different from that of the secondary winding, which can be regarded as an asymmetric three-phase motor, which can improve the starting performance and speed regulation ratio. Because the capacitor is connected at the midpoint of the main winding, the voltage of the capacitor will not exceed 200 volts at high speed, so a capacitor with lower withstand voltage and larger capacity can be used to reduce the cost.

3, electronic speed regulation method

Electronic speed regulation method is made by using the semiconductor principle of silicon controlled rectifier. Its characteristic is that the adjustment of wind speed is not limited. Because the potentiometer has no grade, it can be adjusted at will according to personal preference.