What is an Inverter?

The concept of inverters in the field of Electricity

An inverter is a device that converts constant time current (DC) into time variable current (AC). Specifically, the inverter usually converts a constant voltage over time (in the battery) into a variable voltage in the form of a sine. In addition, today's inverter also integrates a number of functions to convert from one form of AC to another. For example, you can convert square pulse voltage, sawtooth pulse into sinusoidal voltage.

Theory of Inverters

The theory of inverters is associated with the question: how to convert DC current to AC current?

Note that high quality AC current will have a sine waveform. The oscillator circuit consisting of a capacitor (C) and a coil (L) also has a sine waveform, this is an L-C oscillator circuit. So the simple way is to charge the capacitor so that the circuit oscillates in pure sine waveform.

Basic and simple circuit to convert DC to AC:

Simple circuit to convert DC to AC

Part	Total Qty.	Description	Substitutions
C1, C2	2	68 uf, 25 V Tantalum Capacitor
R1, R2	2	10 Ohm, 5 Watt Resistor
R3, R4	2	180 Ohm, 1 Watt Resistor
D1, D2	2	HEP 154 Silicon Diode
Q1, Q2	2	2N3055 NPN Transistor (see "Notes")
T1	1	24V, Center Tapped Transformer (see "Notes")
MISC	1	Wire, Case, Receptical (For Output)

Notes:

1. Q1 and Q2, as well as T1, determine how much wattage the inverter can supply. With Q1,Q2=2N3055 and T1= 15 A, the inverter can supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power.
2. The easiest and least expensive way to get a large T1 is to re-wind an old microwave transformer. These transformers are rated at about 1KW and are perfect. Go to a local TV repair shop and dig through the dumpster until you get the largest microwave you can find. The bigger the microwave the bigger transformer. Remove the transformer, being careful not to touch the large high voltage capacitor that might still be charged. If you want, you can test the transformer, but they are usually still good. Now, remove the old 2000 V secondary, being careful not to damage the primary. Leave the primary in tact. Now, wind on 12 turns of wire, twist a loop (center tap), and wind on 12 more turns. The guage of the wire will depend on how much current you plan to have the transformer supply. Enamel covered magnet wire works great for this. Now secure the windings with tape. Thats all there is to it. Remember to use high current transistors for Q1 and Q2. The 2N3055's in the parts list can only handle 15 amps each.
3. Remember, when operating at high wattages, this circuit draws huge amounts of current. Don't let your battery go dead :-).
4. Since this project produces 120 VAC, you must include a fuse and build the project in a case.
5. You must use tantalum capacitors for C1 and C2. Regular electrolytics will overheat and explode. And yes, 68uF is the correct value. There are no substitutions.
6. This circuit can be tricky to get going. Differences in transformers, transistors, parts substitutions or anything else not on this page may cause it to not function.
7. If you want to make 220/240 VAC instead of 120 VAC, you need a transformer with a 220/240 primary (used as the secondary in this circuit as the transformer is backwards) instead of the 120V unit specified here. The rest of the circuit stays the same. But it takes twice the current at 12V to produce 240V as it does 120V.

In fact, the electrical signals in electronic circuits are very complex, with many different shapes. So the circuit diagram to convert to current with a "nice" graph is a rather complicated type of electronic circuit.

Today, they also use mathematics in inverter technology. In particular, the Fourier family can be used to calculate total harmonic distortion (THD).

The switch in the simple inverter described above, when not coupled to an output transformer, produces a square voltage waveform due to its simple off and on nature as opposed to the sinusoidal waveform that is the usual waveform of an AC power supply. Using Fourier analysis, periodic waveforms are represented as the sum of an infinite series of sine waves frequencies that are integral multiples of the fundamental frequency. The source: https://en.wikipedia.org/wiki/Power_inverter

Inverters are available in the market

Currently, in the world, there are 2 electrical markets to choose from, that is Amazon's market in the US and Aliexpress's market in China.

American inverter selection on Amazon: Inverter

China's inverter selection: 

• Inverter
• Pure Sine Wave Inverter DC 12v/24v To AC 110V/220V 1000W 1600W 2000W 3000W

Comment: Actually, China's technology has the support of the elite in the background. It is not natural that China has emerged as a country that produces so many electronic products. This is the problem of the elite, while they are selling expensive goods in the US and Europe, on the other hand, they themselves create cheap goods.

Pure Sine Wave Inverter 8000W 7000W 5000W 4000W 3000W Power Inverter 2000W DC12V/24V TO 120V 220V 230V 240V&Remote Controller

More details: Pure Sine Wave Inverter 8000W

Benefits of using an inverter

Any type of device when using them has one or several certain uses, and inverters are one of them. And in my opinion, when using inverters, we will get the following benefits:

• Easily change the motor speed, reverse the motor rotation direction.
• The inrush current is reduced compared to direct starting, star-delta starting, so there is no voltage drop or difficulty in starting.
• The process of starting through the low-speed magnetic inverter helps to prevent the motor carrying a large load from having to start suddenly, avoiding damage to the mechanical part, the bearing, and increasing the life of the motor.
• Significant energy savings compared to direct motor driving.
• Inverters usually have electronic systems for overcurrent, overvoltage and undervoltage protection, creating a safe system for operation.
• Thanks to the working principle of inverting through diodes and capacitors, the reactive power from the motor is very low, thus reducing the current significantly during operation, reducing costs in installing capacitors, and minimizing waste. power loss on the line.
• The inverter is integrated with communication modules that make control and monitoring from the center very easy.
• Important: Homemade generators also require an inverter. This is an important device for anyone who uses kinetic energy to generate electricity for the house.

When you successfully build your own generator, then the benefit is in reducing your electricity bills, or living off the grid. However, using an inverter will make the power quality better.

Notes when using the inverter

In the process of using the inverter, we need to pay attention to a number of issues to be able to ensure that the equipment is compatible and best. Specifically, we need to pay attention to a number of related issues such as:

• We need to base on the parts, stages, production stages then determine the required power for the engine. This will serve as a premise for choosing the right inverter, helping to avoid waste as well as ensure sufficient capacity for that production process.
• The components inside the inverter are very sensitive to environmental conditions, so care should be taken to ensure the longevity as well as the accuracy and stability of the device.
• It is necessary to calculate between ways to change the engine speed accordingly. In addition to the inverter, we can completely adjust the speed and reverse by starting star, delta or soft start.
• The first time you interact and work with inverters, you need to spend a lot of time learning about the technical characteristics as well as the correct usage methods. Note about the process, how to use, install to ensure safety - good operation - high efficiency.