Welding machines of direct and alternating current. Inverter: DC or AC? Electrodes and features of work

When choosing welding, buyers have a question: buy a DC or AC inverter welding machine? Both types of inverters have their advantages and disadvantages, but it is worth noting that today AC welding is a thing of the past, they are being replaced by more advanced rectifier or DC welding machines.

Which device to choose?

What to choose - a rectifier or a transformer?

AC welding machines have the following advantages:

simple design;
minimum breakdowns, large working resource;
the ability to regulate the strength of the weld current.

The disadvantages of such devices are quite significant:

low efficiency;
spattering of metal during welding;
large dimensions.

- modern welding inverters that convert current into direct current. Advantages of rectifiers:

high quality welds;
high efficiency;
the ability to regulate the current strength, a protective block;
welding of any metals, incl. low-alloyed, etc.

DC inverters have practically no drawbacks, and are affordable for every consumer group.

How to measure the current strength of a welding inverter?

The main characteristic of welding inverters is the current strength, the higher it is, the more productive the device will be. The cost of welding also directly depends on this indicator.

For domestic use, an inverter with parameters up to 160 A, connected to a 220 V power supply, is sufficient. If there are power surges in the mains, it is recommended to purchase a semi-professional device with current characteristics of 200 A. It is not difficult to measure the current of the device. Usually, this indicator of a serviceable inverter corresponds to that declared by the manufacturer, but if there is doubt about the health of the device, then the readings can be measured using a digital millivoltmeter or a pointer microammeter. However, please note that the readings of the instruments depend on the length of the welding arc, the diameter of the electrode, and the correctness of the measurement.

Also an important indicator is the power of the welding machine. As a rule, it is not indicated in the passport, but knowing the maximum current output by welding and other parameters, you can calculate the amount of kW consumed.

In the twentieth century, the AC welder was the most common metal welding device in construction and industry. This is due to the simple design of the device.

In short, it is a power step-down transformer, the secondary winding of which has several leads. Depending on what metal needs to be welded, what thickness, what electrode, the welder chooses one or another output of the secondary winding.

Welding machines operating due to the action of alternating current are divided into the following types:

equipment for manual arc welding using individual electrodes coated with flux;
equipment for manual argon electric welding using non-consumable tungsten electrodes;
semi-automatic equipment for welding in a protective and inert gas environment using an electrode wire;

In the international classification, electric arc welding received the designation MMA-AC or MMA-DC, in the case of manual electric welding with single electrodes, and argon welding with non-consumable electrodes - TIG.

Construction on transformers

A conventional welding machine in size and shape looked like a household washing machine on wheels, only even heavier. The closed magnetic circuit was located vertically. Below was the primary winding of the transformer.

The secondary winding was movable. It was attached to the nut of a vertical screw with a tape thread. An eyebolt with a handle was located on the housing cover.

When the handle was rotated, the nut with the secondary winding moved along the screw, changing the magnetic flux passing through the coils. Thus, the adjustment of the welding electric current was carried out.

To move the apparatus, there was a handle on the cover, and a clamp was located on the side wall to connect the wires of the welding chain. All walls had slotted holes for transformer cooling.

Speaking of such devices in the past tense, it means that now most of them use AC and DC welding inverters. Welding equipment based on a power transformer is practically not used.

The second option: adjustment is carried out by changing the gap between the primary and secondary coils. In this case, a change in the electric current in a wide range does not lead to a change in the arc voltage, which has a positive effect on the quality of the weld.

Contact welding equipment

In contact welding machines at the time of the welding process, for low-power devices, the welding current reaches 5000-10000 A, in powerful devices it reaches 500 kA. Therefore, high demands are placed on transformers.

They are step-down transformers with a number of design features:

to get the maximum electric current, the secondary winding is made from one turn;
the primary winding is carried out on a disk core in the form of separate sections. The breakdown of the coils into sections is necessary to regulate the electric current, and the disk for uniform cooling;
the secondary winding is made in the form of copper disks connected in parallel. To protect against moisture, they are filled with epoxy resin;
air or water cooling is provided.

The devices experience high mechanical loads, up to 400 starts per minute, so they are subject to additional requirements for structural strength.

Low-power contact welding machines have a welding current of up to 5000 A, weigh about 20 kg and weld metal up to 2.5 mm thick. Widely used at home and small workshops.

Inverter design

Inverters are sometimes referred to as DC welders because their first step is to convert the AC voltage to DC.

Inverters are actively replacing devices on transformers due to their low weight, compact size and high performance.

The welding inverter consists of a high-voltage rectifier diode bridge and a low-pass filter, a frequency generator in the range of 30-70 kHz, high-voltage power switches, an isolation capacitor and a step-down transformer. It performs the function of converting low-frequency alternating current into high-frequency.

At the output of the keys, thanks to the control unit based on a frequency generator, a signal with a frequency of 30-70 kHz is obtained. Passing through the isolation capacitor, the electric current gets rid of the constant component and enters the primary winding of the step-down transformer.

At the output of the secondary winding, a high-frequency alternating current is obtained, which is used for welding. In fact, AC welding inverters are performed as switching power supplies without a rectifier unit at the output.

Due to the fast zero crossing, AC inverter welding machines have a stable, uniform arc, which has a positive effect on the quality of the seam.

Using an inverter allows you to get a small-sized device of high power. The disadvantage of the inverter can be considered high sensitivity to power surges.

Advantages and disadvantages

AC manual arc welding works on the basis of a power transformer, which has a simple, reliable and inexpensive design. It can work in almost any conditions and for a long time without interruption.

The disadvantages include the low productivity of welding, the need for constant removal of slag. The weld is worse than direct current welding.

Argon welding using an alternating current apparatus with non-consumable electrodes gives a weld of the highest quality, allows you to weld large-section metal, there is no spatter.

The disadvantages include the need to use additional equipment in the form of gas cylinders and low productivity.

Electrodes and features of work

For welding with alternating electric current, electrodes have been developed for a long time and have a wide variety. When using inverters, it was necessary to create new electrodes due to the specifics of high-frequency alternating current.

The most widely used electrodes are brands ANO, OZS, MR. They are used for welding carbon and low alloy steels. They provide easy ignition of the electric arc and uniformity of its maintenance, easy removal of slag. Can be used for AC and DC welding machines.

This often leads to the porosity of the seam, reducing its quality. When using high-frequency alternating electric current, this disadvantage is practically overcome.

The use of constant allows you to get welds of higher quality due to the uniform release of heat in the weld pool. With direct current, the electric arc ignites at a lower voltage and is easier for the welder to maintain.

Numerous low quality fakes are forcing people to make their own AC and DC welding inverters, which are more reliable and easier to repair. How to make such a unit with your own hands and make it durable and efficient in conditions of unstable voltage in the country and in the countryside? We will answer this question in this publication and gradually assemble a reliable and practical welding inverter for connecting different parts. Our task is to ensure the small dimensions of the equipment and the light weight of the end device for the convenience of working with it.

For a reliable connection of metals in any construction, welding machines are used, the basis of which is a power transformer that serves as a voltage and current converter. According to the principle of operation, welding units are divided into the following types:

Until recently, the most popular was the DC welding machine, the main disadvantage of which was significant weight. At the same time, the simple design of such a product made it possible at home to make a homemade product that is not inferior to industrial designs. In addition to the power transformer, the design includes rectifier diodes and a large-capacity smoothing capacitor, as well as chokes and resistors. Thus, it is not so difficult to assemble a welding machine with your own hands.

An AC welding machine looks even simpler, which is a power transformer, in the secondary winding of which several conclusions are made with a different number of turns. This is done to adjust the welding current depending on the thickness of the material being joined. Such AC welding machines are easy to manufacture, but have poor operating comfort, although the seam is more uniform and stronger.

Three-phase units are made of three transformers connected in a star with six diodes connected in a three-phase bridge circuit. Such a connection allows you to consume a small current and distribute the load evenly over the phases.

Next, consider welding inverters with high frequency alternating current, which are distinguished by low weight and dimensions. The essence of their work is that the alternating mains voltage of 220 volts with a frequency of 50 Hz is rectified and then converted into a high-frequency alternating voltage of 20-50 kHz. This approach allows you to reduce current consumption and reduce the weight of the unit without compromising its technical characteristics.

It is important to remember that homemade DC welding machines are used only with the appropriate electrodes.

Advantages of a homemade inverter

For construction work using metal structures, it is desirable to have your own welding machine, but its price in retail chains is often too high. You can assemble a home-made welding machine that will reduce the cost of the final product, but you still cannot do without certain costs. In particular, the cost of high-frequency transistors, as well as a thyristor current regulator for the welding machine and rectifier diodes, will become necessary.

The inverter has the following advantages:

light weight, about 10 kg, depending on the power;
efficiency - more than 90%;
low power consumption;
wide operating limits of current regulator circuits, which allows you to work using different technologies for welding elements from different metals;
high voltage stability on the electrode allows you to make a smooth and high-quality seam;
different types of electrodes can be used;
modern circuits and elemental base make it possible to eliminate sticking of electrodes and provide accelerated ignition of the arc.

Necessary accessories and tools

We see that the inverter in welding work is an indispensable tool, easy and convenient to use. In order to ensure its high-quality assembly, you will need, in addition to radio components, the following tools:

powerful soldering iron with solder and flux;
a set of screwdrivers and pliers;
electric drill or screwdriver with a set of drills;
hacksaw, knife, scissors;
suitable housing for mounting the inverter.

Since the operation of the inverter is accompanied by heating of the elements, it is necessary to provide a forced ventilation system, and place diodes and transistors on radiators.

To understand the essence of the assembly of the device, it is necessary to understand the concept of the device and the interaction of its components with each other. The welding inverter consists of the following main components:

mains voltage 220 V, 50 Hz is supplied to the primary low-frequency diode rectifier, after which the DC voltage is filtered by capacitors;
DC voltage is applied to the inverter, which produces a high-frequency AC voltage at the output;
next is a step-down transformer;
then a secondary high-frequency rectifier;
direct current through the inductor goes to the electrode;
from the input and output of the high-frequency transformer, a connection is made to the feedback unit, which corrects the operation of the inverter depending on the parameters of the welding current;
welding inverter control unit.

Assembly sequence of the welding machine

Self-assembly of the inverter involves the use of as many ready-made elements as possible, since this unit is quite complex and one cannot do without knowledge of the basics of radio electronics. For the final check and debugging, you will need an oscilloscope and a tester designed to measure high currents.

You can independently rewind the transformer, adapting it to your needs, or create a choke. It is possible to place diodes and thyristors on radiators, to fix tires from aluminum or copper strips, but it is possible to assemble and debug feedback and control units only with the help of a specialist.

When assembling the welding machine, it is very important to follow the safety rules, since electrical equipment is associated with the risk of electric shock.

When carrying out work on the installation of inverter units, it is necessary to comply with a number of requirements, namely:

the case for the device must be chosen so that all the elements of the inverter are placed in it compactly, but not crowded;
when winding a transformer, it is necessary to monitor the dense laying of the winding turns, securely isolate them and fix them;
power diodes, thyristors and transistors are securely fixed on radiators using heat-conducting paste;
it is best to use copper wires and tires, since their conductive properties are higher than that of aluminum;
the quality of all components should be treated very carefully, because the durability of the device depends on them;
ensure the smooth operation of the cooling system with the help of powerful fans, and drill holes in the case for air circulation;
carefully solder all electrical connections.

The final debugging of the welding inverter should be carried out under the supervision of a specialist.

Results

When assembling a welding inverter with your own hands, you will provide yourself with an indispensable and convenient device for welding metals, and in addition, you can save a lot. It is important to take a responsible approach to the choice of parts and electronic components, and if necessary, seek help from professionals. In the final debugging, their help and equipment will ensure the perfect and long-term operation of the inverter.

DC welding (TIG DC)- this is one of the types of argon-arc welding, which is used for high-quality joining of most metals that do not form a refractory oxide film on the surface of the product during the melting process.

Principle of operation welding machines with direct current (TIG DC) is based on pulse-width modulation or PWM. The inverter circuit is represented by powerful transistors that rectify the mains voltage and convert it into an alternating high-frequency voltage up to 100 kHz. Further, the voltage is supplied to the primary winding of the transformer, and from the secondary winding the high-frequency alternating voltage is converted into a constant voltage.

TIG welders can weld with both "straight" and "reverse" polarity. "Direct" polarity is used for high-quality welding of titanium, high-alloy steel and other metals. With "straight" polarity, there is a minimum heating of the electrode and maximum penetration of the metal being processed. With “reverse” polarity, TIG machines allow using cathode sputtering to remove the oxide film (Al2O3), which is formed during the welding of aluminum and other refractory metals. However, in this case, due to the strong heating of the electrode, the tungsten electrode quickly burns out.

Arc excitation when working with TIG DC devices occurs between the metal and the tungsten electrode, to which the welding current is applied. At the same time, a protective gas (argon) is supplied to the welding zone through special nozzles in the TIG torch, which creates a shell and excludes the influence of the atmosphere on the formation of the seam.

Modern welding equipment of the TIG DC series is used for processing products made of high-alloy and stainless steels, carbon and medium-alloy steels, titanium and copper, zinc, alloys based on them and other metals.

Universal TIG DC devices are used for repair and production work, in the field of construction, in the manufacture of ventilation and heating systems, in the chemical and food industries, in machine tool building, in the production of pipelines, etc.

Advantages of DC welding (TIG DC):

high quality of welding connection;
no spattering of metal;
the ability to perform welding in any spatial position;
absence of slag formations;
practically no seam modification is required;
excellent visual control of the welding arc and seam formation.

Disadvantages of DC welding (TIG DC):

Welding experience required
the difficulty of welding outdoors in strong winds or drafts;
use of a gas cylinder with argon;
low performance.

In the Welcome section to the question of AC and DC welding machines, what is the difference? given by the author Evgeny Savchuk, the best answer is a different arc - different electrodes ... The device of welding transformers: under the body there is a core - a closed magnetic circuit, primary and secondary windings. Passing through the primary winding, the current magnetizes the core. The magnetic flux on the secondary winding induces an alternating current. The voltage of the resulting alternating current depends on the number of turns on the secondary winding. The larger the secondary winding, the higher the voltage. The result of the work is alternating welding current; a DC welding transformer includes a rectifier in its design. DC welding provides a higher quality welded joint than AC welding. Due to the absence of zero current values, the stability of the arc burning is increased, the penetration depth is increased, spatter is reduced, arc protection is improved, the strength characteristics of the weld metal are increased, the number of weld defects is reduced, and reduced spatter improves the use of filler material and simplifies the operations of stripping the welded joint from slag and frozen splashes of metal. All this has led to the fact that direct current welding is more used for welding high-quality seams of critical joints.

2oa.ru

What is the difference between a welding machine and an inverter?

If it is necessary to independently carry out welding work, the question arises: what type of welding machine to purchase. Welding is the creation of permanent connections between the parts to be welded at the atomic level. The welded joint is one of the most durable and therefore is used quite often.

In electric welding, heating and melting of the metal occurs due to the formation of an electric arc between the end part of the electrode and the surface to be welded. Sources of formation and maintenance of the arc are divided into several types:

Transformer.
Inverter.
Rectifiers.
Welding units based on an internal combustion engine.

Consider the two types that have found the most widespread use: a transformer-based welding machine and an inverter source of an electric arc.

This is the simplest of the welding machines, using the alternating current of the network. Works at the expense of the transformer which regulates tension of a network to welding. Transformer or induction welding machines are divided according to the following features:

Power (the greater the welding current, the thicker the metal can be processed).
The number of posts, that is, jobs (how many people can work at the same time).
Voltage (single-phase or three-phase network).

Its advantage is a simpler and more reliable design, low cost, high maintainability.

transformer welding machine

The disadvantages include the dependence of the arc on power surges, large weight and overall dimensions, strong heating during work.

What is an inverter?

An inverter welding machine or simply an inverter is one of the energy sources for electric arc welding, which is based on the use of high frequency current. Its work is carried out due to power electronics and a small transformer.

inverter welding machine

Its advantages are recognized as low power consumption, compactness, small weight and dimensions, and a sufficiently high quality of the seam.

The disadvantages of the inverter include relatively high cost, fear of moisture, dust and low temperatures (typical for budget models), sensitivity to power surges, expensive repairs.

What do inverter and transformer welding machine have in common

The similarity of these devices in their purpose is the formation and maintenance of an electric arc. But there are some other things that they have in common:

The considered devices are united by the presence of a transformer, but of different sizes. By pre-acquiring high frequency current, the inverters do not require large transformers. To obtain a current of 160 A, a transformer weighing 0.25 kg is needed. To obtain the same current in inductive devices, a transformer weighing 18-20 kg is required.
Possibility of smooth adjustment of current. Transformer devices have such an opportunity due to a change in the size of the air gap in the magnetic circuit.
The devices are powered by household (220V) or industrial (380V) mains.
Most welding machines have short circuit protection.

What is the difference between inverter and transformer source of electric arc

The dimensions and weight of the transformer type welding machine are larger than those of the inverter. Industrial designs can weigh more than one hundred kilograms.
Operating principle. In the inverter, the alternating current of the network is converted by the primary rectifier into direct current, then again into high-frequency alternating current, and then again there is a change to direct current at the secondary rectifier. For transformer-type welding machines, the current strength changes due to a change in the position of the magnetic circuit, that is, the core of a step-down transformer or the inclusion of a different number of winding turns in the circuit.
The inverter has a more stable arc due to the stability of the welding current, which affects the quality of the seam.
Design difference. The inverter is more complex and can be equipped with the following additional features: HOT START - increase the initial current to improve the ignition of the welding arc. ARC FORCE - an increase in welding current to accelerate the melting process and prevent sticking, that is, the arc is forced. ANTI-STICK - reduction of current when the electrode sticks to increase the time for its separation and protection against overload.
The process of learning to work on a transformer is more complex and time-consuming. However, having mastered these skills, you can easily work on an inverter.
The inverter produces a direct current, the transformer operates on an alternating current with a household power supply frequency of 50 Hz.
The power factor of the inverter is the largest of all welding equipment, and the efficiency exceeds transformer analogues by 20-30%.
Wide range of welding current.
The inverter has such an indicator as the coefficient of intermittent operation (KP). It determines the time of continuous operation at the maximum welding current. That is, if the CP is 50%, then after 10 minutes of operation it needs 5 minutes to cool down. There are no such requirements for a transformer welding machine.
Possibility of using electrodes designed for both direct and alternating current.

To date, the market has a fairly wide selection of welding equipment from various manufacturers. The choice of welding machine should be made on the basis of the tasks that are to be performed with its help.

vchemraznica.ru

Advantages and disadvantages of AC welding machines

In the twentieth century, the AC welder was the most common metal welding device in construction and industry. This is due to the simple design of the device. In short, it is a power step-down transformer, the secondary winding of which has several leads. Depending on what metal needs to be welded, what thickness, what electrode, the welder chooses one or another output of the secondary winding.

Device types

Welding machines operating due to the action of alternating current are divided into the following types:

equipment for manual arc welding using individual electrodes coated with flux;
equipment for manual argon electric welding using non-consumable tungsten electrodes;
semi-automatic equipment for welding in a protective and inert gas environment using an electrode wire;
contact welding equipment.

Construction on transformers

The secondary winding was movable. It was attached to the nut of a vertical screw with a tape thread. An eyebolt with a handle was located on the housing cover. When the handle was rotated, the nut with the secondary winding moved along the screw, changing the magnetic flux passing through the coils. Thus, the adjustment of the welding electric current was carried out. To move the apparatus, there was a handle on the cover, and a clamp was located on the side wall to connect the wires of the welding chain. All walls had slotted holes for transformer cooling.

Speaking of such devices in the past tense, it means that now most of them use AC and DC welding inverters. Welding equipment based on a power transformer is practically not used.

In order for the weld to be of high quality, a steeply falling current-voltage characteristic of the transformer is required. This is achieved in two ways. The first option: in a transformer with normal magnetic scattering and a separate reactive coil (choke), the welding process is adjusted by changing the gap in the choke core. The second option: adjustment is carried out by changing the gap between the primary and secondary coils. In this case, a change in the electric current in a wide range does not lead to a change in the arc voltage, which has a positive effect on the quality of the weld.

Contact welding equipment

They are step-down transformers with a number of design features:

to get the maximum electric current, the secondary winding is made from one turn;
the primary winding is carried out on a disk core in the form of separate sections. The breakdown of the coils into sections is necessary to regulate the electric current, and the disk for uniform cooling;
the secondary winding is made in the form of copper disks connected in parallel. To protect against moisture, they are filled with epoxy resin;
air or water cooling is provided.

Contact welding machines are mostly single-phase with armored cores. Since the quality of welding is highly dependent on the duration of the welding pulse, the switching equipment is quite complex - the price for accuracy. The devices experience high mechanical loads, up to 400 starts per minute, so they are subject to additional requirements for structural strength.

Low-power contact welding machines have a welding current of up to 5000 A, weigh about 20 kg and weld metal up to 2.5 mm thick. Widely used at home and small workshops.

Inverter design

Inverters are sometimes referred to as DC welders because their first step is to convert the AC voltage to DC.

Inverters are actively replacing devices on transformers due to their low weight, compact size and high performance.

The voltage of 220 V 50 Hz is supplied to the rectifier bridge, where it is rectified, the filter reduces ripples and is fed to electronic keys made on insulated gate bipolar transistors or field effect transistors. At the output of the keys, thanks to the control unit based on a frequency generator, a signal with a frequency of 30-70 kHz is obtained. Passing through the isolation capacitor, the electric current gets rid of the constant component and enters the primary winding of the step-down transformer. At the output of the secondary winding, a high-frequency alternating current is obtained, which is used for welding. In fact, AC welding inverters are performed as switching power supplies without a rectifier unit at the output.

Due to the fast zero crossing, AC inverter welding machines have a stable, uniform arc, which has a positive effect on the quality of the seam. Using an inverter allows you to get a small-sized device of high power. The disadvantage of the inverter can be considered high sensitivity to power surges.

Advantages and disadvantages

AC manual arc welding works on the basis of a power transformer, which has a simple, reliable and inexpensive design. It can work in almost any conditions and for a long time without interruption. The disadvantages include the low productivity of welding, the need for constant removal of slag. The weld is worse than direct current welding.

Argon welding using an alternating current apparatus with non-consumable electrodes gives a weld of the highest quality, allows you to weld large-section metal, there is no spatter. The disadvantages include the need to use additional equipment in the form of gas cylinders and low productivity.

Electrodes and features of work

The main feature of AC welding is to change the polarity of the current flowing through the electric arc. Due to the fact that at a frequency of 50 Hz the zero-crossing time is quite long, the arc almost goes out, it turns out to be uneven. This often leads to the porosity of the seam, reducing its quality. When using high-frequency alternating electric current, this disadvantage is practically overcome. The use of constant allows you to get welds of higher quality due to the uniform release of heat in the weld pool. With direct current, the electric arc ignites at a lower voltage and is easier for the welder to maintain.

svaring.com

What is the difference between AC and DC?

Only a few are able to really realize that AC and DC are somehow different. Not to mention naming specific differences. The purpose of this article is to explain the main characteristics of these physical quantities in terms understandable to people without technical knowledge, as well as to provide some basic concepts related to this issue.

Difficulties of visualization

Most people find it easy to understand concepts such as "pressure", "quantity" and "flow" because they constantly encounter them in their daily lives. For example, it is easy to understand that increasing the flow when watering flowers will increase the amount of water coming out of the garden hose, while increasing the water pressure will make it move faster and with more force.

Electrical terms such as "voltage" and "current" are usually difficult to understand because you cannot see or feel the electricity moving through cables and electrical circuits. Even for a novice electrician, it is extremely difficult to visualize what is happening at the molecular level or even clearly understand what an electron is, for example. This particle is beyond the human sensory capabilities, it cannot be seen and cannot be touched, except when a certain amount of them does not pass through the human body. Only then will the victim definitely feel them and experience what is usually called an electric shock.

However, exposed cables and wires seem completely harmless to most people only because they can't see the electrons just waiting to take the path of least resistance, which is usually ground.

Analogy

It's understandable why most people can't visualize what's going on inside ordinary conductors and cables. Trying to explain that something is moving through metal goes against common sense. At its most basic level, electricity is not so different from water, so its basic concepts are fairly easy to grasp if you compare an electrical circuit to a plumbing system. The main difference between water and electricity is that the former fills something if it manages to escape from the pipe, while the latter needs a conductor to move the electrons. Visualizing the piping system makes it easier for most to understand the technical terminology.

tension as pressure

Voltage is very similar to the pressure of electrons and indicates how fast and with what force they move through a conductor. These physical quantities are equivalent in many respects, including their relation to the strength of the conduit-cable. Just as too much pressure ruptures a pipe, too much voltage destroys or pierces the shielding of a conductor.

current as flow

Current is the flow of electrons, indicating how many of them move along the cable. The higher it is, the more electrons pass through the conductor. Just as large amounts of water require thicker pipes, high currents require thicker cables.

The use of the water loop model makes it possible to explain many other terms. For example, power generators can be thought of as water pumps, and an electrical load can be thought of as a water mill that requires water flow and pressure to turn. Even electronic diodes can be thought of as water valves that only allow water to flow in one direction.

D.C

What is the difference between direct and alternating current, it becomes clear already from the name. The first is the movement of electrons in one direction. It is very easy to visualize it using the water loop model. It is enough to imagine that water flows through the pipe in one direction. Common devices that produce direct current are solar cells, batteries, and dynamos. Almost any device can be designed to be powered by such a source. This is the almost exclusive prerogative of low voltage and portable electronics.

Direct current is quite simple, and obeys Ohm's law: U \u003d I × R. Load power is measured in watts and is equal to: P \u003d U × I.

Because of the simple equations and behavior, direct current is relatively easy to comprehend. The first power transmission systems developed by Thomas Edison back in the 19th century used only it. However, the difference in AC and DC soon became apparent. The transmission of the latter over considerable distances was accompanied by large losses, so after a few decades it was replaced by a more profitable (then) system developed by Nikola Tesla.

While commercial power grids across the planet now use AC, the irony is that advances in technology have made the transmission of high voltage DC over very long distances and under extreme loads more efficient. Which, for example, is used when connecting separate systems, such as entire countries or even continents. This is another difference between AC and DC. However, the former is still used in low voltage commercial networks.

Direct and alternating current: the difference in production and use

Whereas alternating current is much easier to produce with a generator using kinetic energy, batteries can only create direct current. Therefore, the latter dominates in power circuits for low-voltage devices and electronics. Batteries can only be charged with DC, so mains AC is rectified when the battery is the main part of the system.

A common example is any vehicle - motorcycle, car and truck. The generator installed on them creates alternating current, which is instantly converted to direct current using a rectifier, since there is a battery in the power supply system, and most electronics require constant voltage to work. Solar cells and fuel cells also only produce direct current, which can then be converted to alternating current if needed using a device called an inverter.

Direction of travel

This is another example of the difference between DC and AC. As the name suggests, the latter is a stream of electrons that constantly changes its direction. Since the end of the 19th century, almost all household and industrial electrical systems throughout the world have used sinusoidal alternating current, because it is easier to obtain and much cheaper to distribute, except in very few cases of transmission over long distances, when power losses force the use of the latest high-voltage direct current systems.

AC has another great advantage: it allows energy to be returned from the point of consumption back to the grid. This is very advantageous in buildings and structures that produce more energy than they consume, which is quite possible when using alternative sources such as solar panels and wind turbines. The fact that alternating current allows for bi-directional power flow is the main reason for the popularity and availability of alternative power sources.

Frequency

When it comes to the technical level, unfortunately, it becomes difficult to explain how AC works, because the water circuit model does not quite fit it. However, it is possible to visualize a system in which water rapidly changes direction of flow, although it is not clear how it would do anything useful in doing so. Alternating current and voltage constantly change their direction. The rate of change depends on the frequency (measured in hertz) and is typically 50 Hz for domestic electrical networks. This means that voltage and current change direction 50 times per second. Calculating the active component in sinusoidal systems is quite simple. It is enough to divide their peak value by √2.

When alternating current changes direction 50 times per second, this means that incandescent bulbs turn on and off 50 times per second. The human eye cannot see this, and the brain simply believes that the lighting is on all the time. This is another difference between AC and DC.

Vector mathematics

Current and voltage are not only constantly changing - their phases do not match (they are not synchronized). The vast majority of AC power loads cause phase differences. This means that even for the simplest calculations, vector mathematics must be applied. When working with vectors, it is impossible to simply add, subtract, or perform any other operations of scalar mathematics. With direct current, if one cable receives 5A at some point, and 2A along the other, then the result is 7A. In the case of a variable, this is not the case, because the result will depend on the direction of the vectors.

Power factor

The active power of an AC powered load can be calculated using the simple formula P = U × I × cos (φ), where φ is the angle between voltage and current, cos (φ) is also called the power factor. This is how direct and alternating current differ: the first cos (φ) is always equal to 1. Active power is needed (and paid for) by residential and industrial consumers, but it is not equal to the complex passing through the conductors (cables) to the load, which can be is calculated using the formula S = U × I and is measured in volt-amperes (VA).

The difference between direct and alternating current in calculations is obvious - they become more complex. Even the simplest calculations require at least a mediocre knowledge of vector mathematics.

Welders

The difference between direct and alternating current also manifests itself in welding. The polarity of the arc has a great influence on its quality. Electrode-positive welding penetrates deeper than electrode-negative, but the latter accelerates the deposition of metal. With direct current, the polarity is always constant. With alternating, it changes 100 times per second (at 50 Hz). Welding at a constant is preferable, as it is more even. The difference between AC and DC welding is that in the first case, the movement of electrons is interrupted for a fraction of a second, which leads to pulsation, instability and arc failure. This type of welding is rarely used, for example, to eliminate arc wandering in the case of large diameter electrodes.