Principle and maintenance of household air purifier

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Principle and maintenance of household air purifier [Copy link]

Air purifiers improve indoor air quality by filtering out dust, eliminating odors and harmful gases, and killing bacteria and mold through methods such as adsorption, filtration, catalytic decomposition and release of negative ions.

1. Working Principle

A typical air purifier consists of a high-voltage circuit, a negative ion generator, a micro fan, an air filter, etc. It mainly uses infrared remote control, intermittent operation and other control methods, and the filter types include mechanical, electrostatic and mechanical-electrostatic hybrid.

There are two forms of high voltage generation circuits: one is to directly boost and double the voltage of 220V mains electricity, as shown in Figure 1. The other is to form low-voltage direct current after the mains electricity is stepped down and rectified by a transformer, and then form direct current high voltage through self-excited oscillation boost, rectification, and filtering, as shown in Figure 2. The high voltage generated by both forms of circuits is between kilovolts and tens of thousands of volts. Through the discharge of needle-shaped electrodes, the charged dust is sucked onto the positively charged electrode plate. The air filter uses activated carbon or ferox ketone to absorb odor and filter out harmful substances in the air. The negative ion discharge electrode is a group of needle-shaped metal bodies, as shown in Figure 3. After the power is turned on, the direct current high voltage generated by the high-voltage circuit continuously ionizes the air and produces a large number of positive and negative ions. Because the needle-shaped emitter has negative high voltage, it absorbs positive ions, and the remaining large number of negative ions are repelled by the negative high voltage and blown out by the micro fan to form negative ion wind, achieving the purpose of purifying the air.

2. Common fault troubleshooting

Example 1. The high voltage indicator light is off and the fan does not rotate. Analysis and maintenance: The high voltage indicator light is off, which is usually caused by the power fuse being blown or the high voltage generating circuit being faulty. Check in the following order:

(1) Check whether the fuse is blown. If it is, find out the cause and then replace it.

(2) Check whether the step-up transformer coil is burned out. You can use a multimeter to measure its resistance. If the coil is open or short-circuited, replace the transformer with the same model.

(3) Check whether the rectifier tube and capacitor of the voltage doubler rectifier circuit are damaged and whether the oscillator has stopped oscillating. Use a multimeter to check the relevant components one by one and replace the burned components to eliminate the fault.

Example 2: The high voltage indicator light is on, but the fan does not rotate.

Analysis and maintenance: The high voltage indicator light is on, indicating that the power supply high voltage generation circuit is normal, and the fan may be faulty. First check whether the fan blades are stuck by foreign objects and whether the bearings are severely worn. If there are no abnormalities, check whether the motor leads are broken and whether the windings are damaged. You can use a multimeter to measure. If the windings are open or short-circuited, replace the fan motor with the same specification. Example 3. Sparks between the poles of the negative ion generator.

Analysis and maintenance: The sparks between the electrodes of the negative ion generator may be caused by too much humidity in the ambient air or by the bending and deformation of the positive and negative electrodes. Use tweezers to correct the electrodes first. If the sparks still occur, move the air purifier to a dry place for trial use. This can usually eliminate the fault.

Example 4. The negative ion output concentration is low.

Analysis and repair: There may be too much dust and dirt on the filter and electrodes, and the positive and negative plates may be bent and deformed; it may also be caused by a fault in the high-voltage generating circuit, resulting in too low high voltage. First remove the dirt on the filter and electrodes, and calibrate the positive and negative plates. If it does not work, check the high-voltage generating circuit. Use a multimeter to check the step-up transformer, rectifier tube, capacitor, etc. Note: When cleaning the fan motor and dust on the electrode, be sure to cut off the power supply, unplug the plug, short-circuit the high-voltage electrode to discharge, and use a long-haired brush to remove dust; use tweezers to hold an alcohol cotton ball to clean the electrode seat; do not disassemble the high-voltage electrode of the negative ion generator casually.