Do you know all the basic knowledge about inverters and household inverters?

With the advancement of modern technology, the emergence of inverters has provided considerable convenience for people's lives. Inverters convert direct current energy (batteries, storage batteries) into alternating current (usually 220V, 50Hz sine wave). They are composed of inverter bridges, control logic, and filtering circuits, and are widely used in air conditioning, home cinemas, electric grinding wheels, electric tools, sewing machines, DVDs, VCDs, computers, televisions, washing machines, range hoods, refrigerators, video recorders, massagers, fans, lighting, etc. In foreign countries, due to the high popularity of cars, inverters can be connected to batteries to drive electrical appliances and various tools for work or travel. Below, we will introduce the function, characteristics, working principle, classification, usage precautions, installation and usage methods, common problems, and solutions of inverters.

The function of inverters

1. An inverter converts direct current (battery, battery) into alternating current (usually 220v50HZ sine or square wave). Simply put, an inverter is a device that converts direct current (DC) into alternating current (AC). It consists of an inverter bridge, control logic, and filtering circuit.

2. Widely used in air conditioning, home theaters, electric grinding wheels, electric tools, sewing machines, DVDs, VCDs, computers, televisions, washing machines, range hoods, refrigerators, video recorders, massagers, fans, lighting, etc.

3. Simply put, an inverter is an electronic device that converts low voltage (12, 24, or 48 volts) direct current into 220 volts alternating current. Because we usually convert 220 volts of alternating current into direct current for use, the function of the inverter is the opposite, hence the name. We are in a mobile era, with mobile office, mobile communication, mobile leisure, and entertainment. In a mobile state, people not only need low-voltage direct current supplied by batteries or batteries, but also the indispensable 220 volt alternating current in our daily environment, which can be met by inverters. Weiyang Mall has self built efficient intelligent warehousing, with over 100000 types of self operated inventory, providing one-stop authentic spot procurement, personalized solutions, and diversified services such as selection and substitution.

Characteristics of inverters

1. High conversion efficiency and fast startup;

2. Good safety performance: The product has five protection functions: short circuit, overload, overvoltage/undervoltage, and over temperature;

3. Good physical performance: The product adopts an all aluminum shell, with good heat dissipation performance, hard oxidation treatment on the surface, good friction resistance, and can withstand certain external forces of compression or impact;

4. Strong load adaptability and stability.

Working principle of inverter

1. An inverter is a DC to AC transformer, which is actually a process of voltage inversion with a converter. The converter converts the AC voltage of the power grid into a stable 12V DC output, while the inverter converts the 12V DC voltage output by the adapter into high-frequency high-voltage AC power; Both parts also use the commonly used Pulse Width Modulation (PWM) technology. The core components are all PWM integrated controllers, with UC3842 as the adapter and TL5001 as the inverter. The working voltage range of TL5001 is 3.6-40V, and it is equipped with an error amplifier, a regulator, oscillator, PWM generator with dead zone control, low-voltage protection circuit, and short circuit protection circuit inside.

2. Input interface section: The input section has 3 signals, 12V DC input VIN, working enable voltage ENB, and panel current control signal DIM. The VIN is provided by the adapter, and the ENB voltage is provided by the MCU on the motherboard, with a value of 0 or 3V. When ENB=0, the inverter does not work, while when ENB=3V, the inverter is in a normal working state; The DIM voltage is provided by the motherboard, with a range of variation between 0 and 5V. Different DIM values are fed back to the feedback end of the PWM controller, and the current provided by the inverter to the load will also be different. The smaller the DIM value, the greater the output current of the inverter.

3. Voltage start circuit: ENB is a high voltage level that outputs high voltage to light up the backlight tubes of the panel.

4. PWM controller: It consists of the following functions: internal reference voltage, error amplifier, oscillator and PWM, overvoltage protection, undervoltage protection, short circuit protection, and output transistor.

5. DC conversion: A voltage conversion circuit is composed of MOS switching tubes and energy storage inductors. The input pulse is amplified by a push-pull amplifier to drive the MOS tube to perform switching actions, allowing DC voltage to charge and discharge the inductor, so that the other end of the inductor can receive AC voltage.

6. LC oscillation and output circuit: Ensure the required voltage of 1600V for the start of the lamp, and reduce the voltage to 800V after the lamp starts.

7. Output voltage feedback: When the load is working, the feedback sampling voltage plays a role in stabilizing the voltage output of the inverter.

Classification of inverters

1. According to the frequency of AC power output by inverters, they can be divided into power frequency inverters, intermediate frequency inverters, and high-frequency inverters. Inverters with a frequency range of 50-60Hz for power frequency inverters; The frequency of intermediate frequency inverters is generally between 400Hz and over ten kHz; The frequency of high-frequency inverters is generally between tens of kHz to MHz.

2. According to the number of phases output by the inverter, it can be divided into single-phase inverter, three-phase inverter, and multiphase inverter.

3. According to the direction of the output energy of the inverter, it can be divided into active inverters and passive inverters. Any inverter that transmits the electrical energy output by the inverter to the industrial power grid is called an active inverter; An inverter that outputs electrical energy to a certain electrical load is called a passive inverter.

4. According to the form of the inverter main circuit, it can be divided into single ended inverters, push-pull inverters, half bridge inverters, and full bridge inverters.

5. According to the types of main switching devices in inverters, they can be divided into thyristor inverters, transistor inverters, field-effect inverters, and insulated gate bipolar transistor (IGBT) inverters. It can also be classified into two categories: "semi controlled" inverters and "fully controlled" inverters. The former does not have the ability to self turn off, and the components lose their control function after conduction, so it is called a "semi controlled" ordinary thyristor, which belongs to this category; The latter, on the other hand, has the ability to self turn off, meaning that both conduction and turn off without devices can be controlled by the control pole, hence it is called a "fully controlled type". Power field-effect transistors and insulated gate double weight transistors (IGBTs) belong to this category.

6. According to DC power sources, they can be divided into voltage source inverters (VSI) and current source inverters (CSI). The former has a DC voltage that is close to constant and an output voltage that is an alternating square wave; The latter has a nearly constant DC current and an alternating square wave transmission current.

7. According to the waveform of inverter output voltage or current, it can be divided into sine wave output inverter and non sine wave output inverter.

8. According to the control method of inverters, they can be divided into frequency modulation (PFM) inverters and pulse width modulation (PWM) inverters.

9. According to the working mode of the inverter switching circuit, it can be divided into resonant inverters, fixed frequency hard switching inverters, and fixed frequency soft switching inverters.

10. According to the inverter commutation method, it can be divided into load commutation inverters and self commutation inverters.

Precautions for using inverters

1. The DC voltage should be consistent

Each inverter has a DC voltage value connected, such as 12V, 24V, etc. It is required that the battery voltage selected must be consistent with the DC input voltage of the inverter. For example, a 12V inverter must choose a 12V battery.

2. The output power of the inverter must be greater than the usage power of the electrical appliances, especially for appliances with high power during startup, such as refrigerators and air conditioners, a larger margin should be left.

3. The positive and negative terminals must be connected correctly

The DC voltage connected to the inverter is marked with positive and negative poles. Red represents the positive pole (+), black represents the negative pole (-), and the battery is also marked with positive and negative poles. Red represents the positive pole (+), and black represents the negative pole (-). When connecting, it must be positive (red to red) and negative (black to black). The diameter of the connecting wire must be thick enough and the length of the connecting wire should be minimized as much as possible.

4. It should be placed in a ventilated and dry place, careful of rain, and at a distance of more than 20cm from surrounding objects, away from flammable and explosive materials. Do not place or cover other items on the machine, and the operating environment temperature should not exceed 40 ℃.

5. Charging and inverter cannot be carried out simultaneously. When inverting, do not insert the charging plug into the electrical circuit of the inverter output

6. The interval between two power ups should not be less than 5 seconds (cut off input power).

7. Please wipe the machine clean with a dry cloth or anti-static cloth.

8. Before connecting the input and output of the machine, please first correctly ground the outer shell of the machine.

9. To avoid accidents, users are strictly prohibited from opening the computer case for operation and use.

10. When suspecting a malfunction of the machine, please do not continue to operate and use it. Input and output should be cut off in a timely manner, and qualified maintenance personnel or maintenance units should inspect and repair it.

11. When connecting the battery, make sure there are no other metal objects on your hands to avoid battery short circuits and burns to the human body.

12. Based on safety and performance considerations, the installation environment should meet the following conditions for use:

① Dry: Do not soak in water or rain;

② Cool: Temperature between 0 ℃ and 40 ℃;

③ Ventilation: Keep no foreign objects within 5cm on the shell, and ensure good ventilation on other end faces.

Installation and usage methods of inverters

1. Place the converter switch in the OFF position, then insert the cigar head into the cigarette lighter socket in the car, ensuring that it is in place and in good contact;

2. Confirm that the power of all electrical appliances is below the nominal power of G-ICE before use. Insert the 220V plug of the appliance directly into the 220V socket at one end of the converter, and ensure that the sum of the power of all connected appliances in both sockets is within the nominal power of G-ICE;

3. Turn on the converter switch and the green indicator light will light up, indicating normal operation.

4. The red indicator light is on, indicating that the converter has turned off due to overvoltage/undervoltage/overload/overheating.

5. In many cases, due to the limited output of the vehicle cigarette lighter socket, the converter may sound an alarm or turn off during normal use. In this case, simply start the vehicle or reduce the power consumption to restore normal operation.

Common problems and solutions of inverters

1、 Low insulation impedance

Use exclusion method. Remove all the strings on the input side of the inverter, then connect them one by one. Use the function of the inverter to detect insulation impedance when starting up, detect the problem string, and after identifying the problem string, focus on checking whether the DC connector has a water immersed short circuit bracket or a fused short circuit bracket. In addition, check whether there are black spots on the edges of the components that are burned, causing them to leak electricity to the ground grid through the frame.

2、 Low bus voltage

If it occurs during the morning/evening period, it is a normal problem because the inverter is attempting to generate electricity under extreme conditions. If it occurs during normal daytime, the detection method is still the exclusion method, and the detection method is the same as item 1.

3、 Leakage current fault

The leakage current is too high. Remove the input terminal of the PV array and check the peripheral AC power grid. Disconnect both the DC and AC terminals and let the inverter power off for 30 minutes. If it can be restored, continue to use. If it cannot be restored, contact a professional engineer.

4、 DC overvoltage protection

With the pursuit of high-efficiency process improvement in components, power levels are constantly updated and rising. At the same time, the open circuit voltage and working voltage of components are also increasing. In the design stage, temperature coefficient issues must be considered to avoid overvoltage in low temperature situations that may cause equipment hard damage.

5、 No response from inverter startup

Please ensure that the DC input line is not reversed. Generally, the DC connector has a foolproof effect, but the crimping terminal has no foolproof effect. It is important to carefully read the inverter manual to ensure that the positive and negative poles are connected before crimping. The inverter is equipped with reverse short-circuit protection, which can start normally after restoring normal wiring.

6、 Power grid failure

The work of conducting preliminary surveys of heavy load (working hours with high electricity consumption)/light load (resting hours with low electricity consumption) in the power grid is reflected here. By conducting a preliminary survey of the health status of the voltage at the grid connection point, communicating with inverter manufacturers about the power grid situation, and combining technology, it can ensure that the project design is within a reasonable range. Especially in rural power grids, inverters have strict requirements for grid voltage, grid waveform, and grid distance. The main reason for the occurrence of grid overvoltage problems is that the original grid light load voltage exceeds or approaches the safety protection value. If the grid connection line is too long or poorly connected, it can lead to excessive line impedance/inductance, and the power station cannot operate normally and stably.