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Do you know all this little knowledge about inverters?


With development of modern technology, advent of inverters has greatly simplified everyone's life. Inverters convert DC power (batteries, accumulators) into AC power (typically 220V, 50Hz, sine wave), it consists of an inverter bridge. , control logic and filter circuit, widely used in air conditioners, home theater, electric grinding wheel, power tool, sewing machine, DVD, VCD, computer, TV, washing machine, range hood, refrigerator, VCR, massage. In foreign countries, due to high penetration rate of automobiles, you can use inverters to connect batteries to drive electrical appliances and various tools to work when you go to work or travel. The following is an introduction to functions, characteristics, working principle, classification, precautions for use, installation and use methods, common problems and solutions of the inverter.

Do you know all this little knowledge about inverters?

01 Inverter Role

1. The inverter converts DC power (battery, rechargeable battery) into AC power (usually 220v50Hz, sine or square wave). In layman's terms, an inverter is a device that converts direct current (DC) into alternating current (AC). It consists of an inverter bridge, control logic and a filter circuit.

2. Widely used in air conditioners, home theaters, electric grinding wheels, power tools, sewing machines, DVDs, VCDs, computers, TVs, washing machines, range hoods, refrigerators, VCRs, massagers, fans, lighting, etc.

3. Simply put, an inverter is an electronic device that converts low voltage (12 or 24 volts or 48 volts) direct current into 220 volts alternating current. Because we usually use a 220 volt AC rectifier to turn it into DC, and inverter acts in opposite direction, hence name. We live in a "mobile" era, mobile office, mobile communications, mobile leisure and entertainment. When on move, people not only need low voltage DC power provided by batteries or rechargeable batteries, but they also need 220 volt AC power, which is indispensable in our daily environment, and inverters can meet our needs.

02 Inverter functions

1. High conversion efficiency and fast start;

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

3. Good physical performance: The product adopts all-aluminum body with good heat dissipation performance, hard oxidation surface treatment, good friction resistance, and can resist extrusion or impact of a certain external force; /p>

4. High adaptability and stability under load.

03 Inverter operation principle

1. An inverter is a DC-to-AC converter, which is actually process of inverting voltage using a converter. The converter converts AC voltage of power grid into a stable 12V DC output voltage, while inverter converts 12V DC output voltage of adapter into a high-frequency, high-voltage AC current; both parts also use more commonly used pulse-width modulation. (PWM) technique. Its main part is an integrated PWM controller, adapter uses UC3842, and inverter uses TL5001 chip. The operating voltage range of TL5001 is 3.6~40V, and it is equipped with error amplifier, regulator,generator, PWM generator with dead zone control, low voltage protection circuit and short circuit protection circuit.

2. Input interface part: there are 3 signals in input part, DC 12V VIN input, ENB operating voltage and DIM panel current control signal. VIN is provided by adapter, ENB voltage is provided by MCU on motherboard, its value is 0 or 3V, when ENB=0, inverter is not working, and when ENB=3V, inverter is in normal working state; while DIM voltage provided by main board, its change range is 0 to 5V. Different DIM values ​​are returned to feedback terminal of PWM controller, and current supplied by inverter to load will also be different. The smaller DIM value, smaller inverter output current.

3. Voltage Trigger Circuit: When ENB is high, it outputs high voltage to light panel backlight tube.

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

5. DC conversion: The voltage conversion circuit is composed of a switching MOS tube and an inductor for energy storage. The input pulse is amplified by a push-pull amplifier and drives MOS tube to switch, so that DC voltage is charged and discharged. inductor AC voltage is available at one end.

6. LC generation and output circuit: supply 1600V required to start lamp, and reduce voltage to 800V after lamp starts.

7. Output voltage feedback: when load is running, sample voltage is fed back to stabilize inverter output voltage I.

04 Inverter classification

1. According to output frequency of AC inverter, it can be divided into power frequency inverter, medium frequency inverter and high frequency inverter. The power frequency inverter frequency is 50-60Hz; frequency of medium frequency inverter is usually from 400 Hz to more than ten kHz; high frequency inverter frequency is usually more than ten kHz to MHz.

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

3. According to output power of inverter, it can be divided into active inverters and passive inverters. Any inverter that transfers output electrical energy of inverter to industrial grid is called an active inverter; any inverter that transfers output electrical energy of inverter to a specific electrical load is called a passive inverter device.

4. Depending on theInverter main circuit shapes, it can be divided into single-ended inverter, push-pull inverter, half-bridge inverter and full-bridge inverter.

5. According to type of main switching device of inverter, it can be divided into thyristor inverter, transistor inverter, field effect inverter and insulated gate bipolar transistor (IGBT) inverter, etc. It can also be divided into two categories: "semi-controlled" inverters and "fully controlled" inverters. The former does not have a self-shutdown capability, and components will lose control once turned on, which is why it is called a "semi-controlled" conventional thyristor and falls into this category; second has a self-switching ability, i.e. no device Turning on and off of gate electrode can be controlled, so it is called "full control type". High-power FET and double-weight insulated gate transistor (IGBT) belong to this category.

6. According to DC power supply, it can be divided into voltage source inverter (VSI) and current source inverter (CSI). In first, DC voltage is almost constant, and output voltage is an alternating square wave; in second, direct current is almost constant, and output current is an alternating square wave.

7. According to waveform of output voltage or current of inverter, it can be divided into a sinusoidal output inverter and a non-sinusoidal output inverter.

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

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

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

05 Inverter requires attention

1. The DC voltage must be same.Each inverter has access to DC voltage values ​​such as 12V, 24V, etc.) The selected battery voltage is required to match DC voltage. inverter input voltage. For example, a 12V inverter should select a 12V battery.

2. The output power of inverter should be larger than power used by electrical appliances. Especially for electrical appliances with high starting power, such as refrigerators and air conditioners, a larger margin should be left.

3. The positive and negative poles must be properly connected

The DC voltage connected to inverter is marked with positive and negative poles. Red - it will putThe green pole (+), black is negative pole (-), and positive and negative poles are also marked on battery, red is positive pole (+), black is negative pole (-). (black to black). The diameter of connecting wire should be thick enough, and length of connecting wire should be as short as possible.

4. It should be placed in a ventilated and dry place, beware of rain, and be more than 20cm away from surrounding objects, away from flammable and explosive materials, and do not place or cover other objects on machine over 40°C.

5. Charging and inverter cannot be done at same time. That is, charging plug cannot be inserted into inverter output circuit when inverted.

6. The interval between two starts must be at least 5 seconds (turn off power input).

7. Use a dry cloth or anti-static cloth. Wipe to keep machine clean.

8. Before connecting input and output of machine, properly ground machine frame.

9. In order to avoid accidents, users are strictly prohibited from opening case for operation and use.

10.If you suspect that machine is defective, please do not continue to operate and use it. The input and output must be turned off in time, and qualified service personnel or a maintenance team must check and repair it.

11. When connecting battery, make sure that there are no other metal objects on your hands, so as not to short-circuit battery and burn human body.

12. Use environment, for safety and performance reasons, installation environment should meet following conditions:①Dry: do not soak in water or rain;②Cool: temperature from 0°C. and 40°C;③Ventilation: Keep foreign objects within 5 cm away from body, and other ends are well ventilated.

06 How to install and use inverter

1. Set converter switch to OFF, then insert cigar head into cigarette lighter socket in car, make sure it is in place and contact is good;

2. Make sure that power of all electrical appliances can be lower than rated power of G-ICE. Insert 220V plug of electrical appliance directly into 220V socket at one end of converter and make sure that sum of power of all connected electrical appliances in two sockets is within rated power of G-ICE;

3. Turn on converter switch, and green indicator light will turn on, indicating that it is working normally.

4. The red LED is on to indicate that inverter has tripped due to overvoltage/undervoltage/overload/overtemperature.

5. In many cases, due to limited power of car cigarette lighterthe inverter gives an alarm or shuts down during normal use. At this time, it can be restored to normal as long as car starts or power consumption is reduced.

07 Common inverter problems and solutions

1. Low insulation resistanceUse elimination method. Disconnect all strings on input side of inverter, and then connect them one by one. Use inverter function to determine insulation resistance when starting inverter to detect problem circuits. After finding problem circuits, focus on checking whether DC jack has a short circuit bracket submerged in water. Or burn short circuit bracket. In addition, you can also check if there are black dots on edge of component itself, which causes component to leak electricity to ground grid through frame.

2. Low bus voltageIf it occurs in morning/night, it is a normal problem because inverter is trying to limit power generation conditions. If it occurs during normal daytime, detection method is still exception method and detection method is same as 1 element.

3. Leakage current failureThe leakage current is too large, remove input end of PV array, and then check AC peripheral network, disconnect DC end and AC end, and power up inverter. turn off for 30 minutes Continue to use it if it is restored to use. If it cannot be restored, contact a professional engineer.

4.DC overvoltage protectionIn pursuit of a highly efficient component improvement process, power level is constantly updated and increased, and open-circuit voltage and operating voltage of components are also increased. The temperature coefficient should be considered at design stage to avoid conditions low temperatures Serious damage to device due to overvoltage.

5. The inverter does not respond when startingPlease make sure that DC input line is not reversed. Generally, DC connector has effect of preventing misoperation, but crimp terminal does not have good protection Read inverter manual carefully to ensure that positive and negative poles are important to compress then. The inverter has built-in reverse polarity short circuit protection and it will start up after normal wiring is restored.

6. Mains failureThis reflects a preliminary study of high load operation (high power working hours) / light load operation (low power rest time), and examines voltage health state of point connected to grid. in advance, inform inverter manufacturers about situationwith power grid and combine technologies to ensure that design of project is within reasonable limits, especially for rural power grids. Inverters have strict requirements for voltage connected to grid, waveform and grid. -connected distance. Most overvoltage problems are caused by light load voltage of source power grid exceeding or approaching safety protection value. If connected line is too long or compression is poor, line impedance / inductive reactance is too large, and power plant cannot work normally and stably .