What is an inverter: principle of operation, types and applications

A DC-DC converter or voltage inverter is a device that converts direct current of lower voltage into alternating current of higher voltage or vice versa. Such devices are variable voltage generators. It can be pulsed, pure or modified sinusoidal. Inverter converters are capable of acting as independent power sources and intermediate elements in the converter system.

Inverters contained in uninterruptible power supplies (UPS) provide a stable supply of electricity to computer equipment and other equipment. In the event of an unexpected power outage, they instantly supply computers with electricity from the backup battery. This makes it possible to save data and shut down the PC correctly.

Large UPS systems use powerful inverters with larger battery capacity. They can provide autonomous power to equipment for a long time, and when normal network power supply is restored, they switch the equipment to it.

History of the appearance of the converter

In the late 1800s, American pioneer electrician Thomas Edison (1847−1931) left his laboratory to demonstrate that direct current (DC) was a better way of delivering electricity than alternating current (AC), which was the new system supported his Serbian rival Nikola Tesla (1856−1943). Edison tried all sorts of clever ways to convince people that AC was too dangerous, from electrocleaning an elephant to advocating the use of AC in the electric chair to control capital punishment. Regardless, Tesla's system won the day, and the world has been running pretty much on the grid ever since.

The only problem is that while many of our appliances are designed to operate with alternating current, low-power generators often produce direct current. This means that if you want to run something like an AC powered gadget from a DC battery in a mobile home, you will need a device that converts the DC to an AC inverter, as it is called.

Price

The most significant impact on the cost of the converter is its power.

There are three main price segments:

Initial . This includes low-power devices (up to 200 W) for powering small appliances. Plugs into the cigarette lighter. They produce a modified sine wave. Cost – up to 1400 rubles.
Average . Inverters with a power of up to 800 W with a modified sine wave. Connects directly to the battery. Cost – 1400 – 5000 rubles.
Supreme . Powerful devices (up to 5 kW) with modified or pure sine wave. Cost – from 5000 rub.

Electricity DC and AC

When science teachers explain the basic idea of electricity as the flow of electrons, they usually talk about direct current (DC). We learn that electrons are a bit like a line of ants, walking along with packets of electrical energy in the same way that ants carry leaves. This is a pretty good analogy for something like a basic flashlight, where we have a circuit (a solid electrical loop) connecting a battery, a lamp, and a switch, and electrical energy is systematically transported from the battery to the lamp until all the battery's energy is depleted.

In larger appliances, electricity works differently. The power source, which comes from a wall outlet, is based on alternating current (AC), where the electricity switches between 50 and 60 times per second (in other words, at a frequency of 50 and 60 Hz). It's hard to understand how AC delivers energy when it's constantly changing its mind about where it's going. If the electrons coming out of the wall socket travel, say, a few millimeters down the cable, then they need to reverse the direction and go back, just like how do they ever get to the lamp on the table to make it light up?

The answer is actually quite simple. Imagine that the space between the lamp and the wall is filled with electrons. When you flip the switch , all the electrons filling the cable vibrate back and forth in the lamp filaments - and this rapid shuffling converts electrical energy into heat and lights the lamp. Electrons do not necessarily have to rotate in a circle to transfer energy: in AS they simply “run in place.”

REPAIR

Anyone with a little knowledge of electronics and working with a soldering iron and a multimeter can repair the inverter with their own hands, since there is nothing extraordinary about it.

In terms of breakdowns, I can probably say that there are no major ones, everything breaks. Lamps, switches, transformers, controllers burn out.

Most often, the backlight inverter fails due to breakdowns of the electrolytic capacitors in the power supply and the power filters of the inverter itself. Losing capacity, swelling and closing the power circuit, they lower the voltage. The keys begin to work with greater overload and burn out.

In LCD TVs, the diodes themselves burn out more often. When repairing a TV, you can replace the entire LED strip or check each one and replace it individually. For example, your TV has 3 strips of LED strips with 7 diodes on each. It is known that their supply voltage is 70 volts. We divide and get 3.3 volts, look for one with a power of 1 watt to ensure normal brightness and make a replacement.

The models of modern inverters are very diverse, but the principles of their construction and operation are almost the same, and this simplifies their repair.

What is an inverter

One of the legacies of Tesla (and his business partner George Westinghouse, boss of the Westinghouse Electrical Company) is that most of the appliances we have in our homes are specifically designed to run on AC power. Appliances that require DC current but draw power from an AC outlet require an additional piece of equipment called a rectifier, typically made of electronic components called diodes, to convert AC to DC.

An inverter does the opposite job, and it's pretty easy to understand. Let's say you have a battery in a flashlight and the switch is closed, so the DC flows through the circuit always in the same direction as the race car around the track. Now, if you take the battery out and turn it around, assuming it's the other way, it will almost certainly still produce light and you won't notice any difference in the light you get - but the electrical current will flow in the opposite way.

Let's say you had lightning-fast hands and they were dexterous enough to turn the battery over 50-60 times per second. Then you would become a kind of mechanical inverter , turning the battery's DC power into AC power at a frequency of 50-60 Hz.

Of course, that's not how the inverters you buy at electrical stores work, although some are truly mechanical: they use electromagnetic switches that quickly switch to the current direction. Inverters like this often produce what's called a square-wave output: current either flows one way or the other way around, or it switches instantly between the two states.

Such sudden changes in direction are dangerous for some types of electrical equipment. At normal AC power, it gradually changes from one side to the other in the form of a sine wave.

Electronic inverters can be used to create this kind of smoothly varying AC output from a DC input. They use electronic components called inductors and capacitors to increase and decrease the output current than the sharp, square wave on/off output you get with a basic inverter.

Inverters can also be used with transformers to change a certain DC input voltage to a completely different AC output voltage (higher or lower), but the output power must always be less than the input power. The law of conservation of energy implies that an inverter and transformer cannot supply more energy than they consume, and some energy must be lost as heat as electricity flows through various electrical and electronic components. In practice, inverter efficiency often exceeds 90 percent, although basic physics tells us that some energy - whatever it is - is always lost somewhere.

How to choose a 220 V welding machine for home and garden

When selecting welding equipment, the consumer must decide what tasks it will be needed for.

If it is used for repairing body parts, then it should have some parameters, and if it is used for the production of metal structures, then it should have different parameters. But in any case, the devices must meet a number of requirements, in particular, functions such as hot start, anti-sticking and some others must be implemented in a home device. This is how inverters differ from traditional devices.

A fan must be installed in the design of this type of device. In addition, the circuit must be protected from power surges. In principle, a device with such parameters can work both in a home workshop and in industrial production conditions.

How the device works

Imagine being a DC battery and someone taps you on the shoulder and asks you to produce an AC battery instead. How would you do it? If all the current you produce flows in one direction, how about adding a simple switch to your output? Turning your current on and off can very quickly provide DC pulses that could do at least half the work. To make a proper AC , you will need a switch that allows you to completely cancel the current and do this about 50-60 times per second. Visualize yourself as a human battery, changing contacts back and forth more than 3,000 times per minute.

Essentially, an old-fashioned mechanical inverter boils down to a switching box connected to a transformer. And since electromagnetic devices that change low-voltage alternating current to high-voltage current or vice versa, using two coils of wire (called primary and secondary) wound around a common iron core.

In a mechanical inverter , either an electric motor or some other automatic switching mechanism reverses the incoming current back and forth basically simply by changing the contacts and generates an AC in secondary mode. The switching device works in the same way as in an electric doorbell. When power is connected, it magnetizes the switch, pulls it out, and turns it off very quickly. The spring will push the switch back, turning it on, and then repeat the process over and over again.

The switching frequency is set by control signals generated by the control circuit (controller). The controller can also solve additional tasks:

Voltage regulation.
Synchronization of key switching frequency.
Protecting them from overloads.

Useful additional features

The most inexpensive inverters can only change the current strength and show an indication of the network and overheating. Most often, the automation turns off the power when the temperature rises. But to make work more comfortable or easier, there are several additional functions.

Anti Stick function

To get an even seam, it is necessary to maintain a clear distance between the end of the electrode and the parts to be welded within 3-5 mm (depending on the current strength). Beginners have difficulty doing this (the hand is not yet used to it), so the electrode often sticks to the surface. The function instantly turns off the voltage and resumes it as soon as contact with the product is broken.

Otherwise, the user must use physical force to tear off the end of the filler material, which results in crumbling of the coating.

Hot Start function

Practical for welding rusty metals or critical joints. The function operates by supplying increased voltage (V) at the start of welding, which ensures easy ignition and eliminates the need to repeatedly knock the end of the electrode on the surface. If this is the front side of the part, then the arc will leave fewer marks, which will then have to be processed mechanically.

Arc Force function

Optimal for beginners whose electrode often sticks. A device with this function “feels” the distance between the contacts and when the arc is about to go out, it briefly adds current (A) to prevent this. This action is also useful when welding thin metals (1.0-1.2 mm), since small values are initially set there (20-40 A), which provokes sticking.

It is better to choose an inverter with a digital display, since this way you can always see the current voltage and current. The drawn scale is usually small and already difficult to distinguish from 3-4 meters.

Inverter with electronic display.

If the machine is equipped with a connector for TIG welding, then the arc decay function is useful, providing a smooth decrease in amperes when the welder releases the button. This will prevent the formation of fistulas at the end of the seam and allow the weld pool to crystallize systematically.

When an inverter machine with argon is used for welding large stainless steel containers or repairing motor housings and gearboxes, the function of remotely adjusting the current strength is practical. It is made in the form of a second button on the burner and allows you to adjust the amperes without approaching the inverter each time.

Technical capabilities of inverter devices

Any inverter, being a welding machine, serves to ignite the welding arc and maintain its combustion in a stable state. Due to the features of its design, the inverter device copes with this task perfectly. In addition to the main function, modern inverter models are equipped with a number of additional options that make their use as convenient and comfortable as possible. These include:

“Hot start” (this option allows you to ignite the welding arc faster, which is achieved by applying an additional electrical pulse to the electrode);
“Arc force” (this function assumes that when the electrode suddenly approaches the surface of the parts being welded, the welding current automatically increases, which prevents the electrode from sticking in such a situation);
“Anti-sticking” (this option works as follows: when the electrode sticks, the electric current stops flowing to it; it starts flowing only when the electrode is torn off from the surface of the parts being connected).

Front panel of the welding inverter "BIMark-170"

Some models of inverter devices are also equipped with overheating indicators and an automatic shutdown option if overheating does occur. This useful function protects such an expensive device as an inverter from burning out and, as a result, from costly repairs.

The additional options described above are especially useful for novice welders, as they help minimize the impact of a specialist’s skill level on the quality of welding.

Inverter UPS

The vast majority of electrical appliances in Russia that modern people use every day are designed for a voltage of 220V-230V.

Chemical voltage sources, batteries capable of storing a charge of electricity for a long time, provide a constant voltage that is too low to power household appliances: 2 volts, 6 volts, 12V, etc. Inverters convert direct voltage from batteries into alternating voltage 220V or 230V, depending on the design and settings. The work of all UPSs is based on this!

Video what is an inverter uninterruptible power supply and how it works

The battery life of the uninterruptible power supply will be proportional to the number and capacity of the batteries connected to the inverter input. But there are other factors that affect the operating time - you can read more here.

Batteries can store a supply of electrical energy for a long time, which allows you to keep a large amount of accumulated electricity in reserve for emergency situations, accumulated in the battery.

If there is a loss of electricity at the input to the distribution board, the inverter automation will instantly transfer the power of the electrical appliances connected to the inverter output to the battery (through an electronic circuit that converts a direct voltage of 12 Volts into an alternating voltage of 220 V with a given frequency (Hz)).

There is no switching in online systems - You can read more here.

The main advantages of electric inverters:

This is environmental safety (no harmful environmental pollution)
Low noise during operation, have a low noise level of the cooling fan several times compared to power plants...
They do not require refueling or constant maintenance.
They have high efficiency and low operating costs, tied to the cost of electricity.
Continuous power supply, no pause (as in power plants) when switching to batteries.
Possibility to increase battery life by increasing the number of batteries.