Current source - a battery of an electrical circuit that provides constant consumption, measured by amperes, or a given form of the law of change of a parameter. This is how welding machines work, the number( diameter) of the electrode corresponds to each metal thickness. The process is provided with direct current. Otherwise, the breakdown of the arc begins, other unpleasant effects occur.
Difference between a Real Source and an Ideal
It is known that the power supply of an electric circuit is limited. As a result, an increase in load causes a change in parameters. The voltage surges of garage cooperatives, cottages, and other specific objects are well known. The substation allocates a limited resource, consumption is rather big. First of all, heating devices( water), welding machines are meant.
Thus, the socket is a voltage source. Voltage is highly dependent on consumer behavior. It is noticed that the morning hours of the substation overload, appropriately taken into account by the regions when charging. As for the ideal sources, it is understood that the parameters are permanent. Until some time, it was impossible to meet such equipment, modern technology limited the scope of the restrictions.
The welding inverter IWM 220 maintains performance in the range of supply voltages of 180-250 volts, giving a constant effective current value to the clamps. Electronic power supplies achieve such high rates by flexible regulation of operating modes. Take the inverters, the principle of action is based on the rectification, filtering voltage of 220 volts, followed by cutting into bundles of pulses. By varying the porosity of the parcels, the length is achieved by changing the current.
The measuring Hall sensor affects, directly or indirectly, the bias voltage of the power switch. There are other, processor, control circuit output parameters of the devices. In the latter case, the processor takes care, carrying the appropriate program, embedded in the memory of a digital code.
For welding, alternating and direct currents are used for ferrous and non-ferrous metals. It is important to understand: the source is able to support any law of parameter changes. This is recognized as a distinctive feature, purpose. Ensures the proper functioning of consumers.
Current Source Operation
Physics textbooks provide examples of current sources:
It is easy to see that galvanic power sources of the chemical principle of operation are completely. The driver knows: the battery is powerless to issue a constant current voltage. Power is limited by the rate of chemical reactions on the plates, plates. As a result, the parameters do not remain constant.
The best example of a current, voltage power supply is an inverter. Electronics flexibly changes the parameters of the device, achieving the desired effect. The output variables, constant voltage currents. Depending on the emerging needs. There are a lot of power voltages in a personal computer: for hard drives, a processor, DVD drives.5, 12, 3.3 V. Each destination, several destinations.
circuit. Thus, the consumer determines whether a constant current is needed, or a voltage generated according to a certain law is required. If you take the welding, the flow rate of charges through the plasma determines the operating temperature of the process, directly determines the conditions of existence of the arc, the depth of metal melting. Technologists have long figured out the conditions, determined experimentally, the leadership of the welding machine writes the following:
- sheet thickness - 3 mm;
- electrode diameter - 3.2 mm;
- Process Operating Current 100 - 140 A.
The welder, with lightning speed, sets the indicated parameters on the IWM 220 case, takes the electrode of the required diameter, presses it with a tongue, leads the second exit to the ground. Then he puts on a mask, starts lightly tapping the details, getting a spark. Not too concerned about the results of labor, the industry benefit of the industry tells you how fast to move along the seam, at what angle to observe the result of the process. The welder knows what to do. To make sure, a special commission on the test results( performance of certain seams) assigns the worker a grade( significantly affects the range of powers, wages).
So, the type of current determines the needs of the ongoing process. In most cases, voltage is required, often the devices initially required constant current. Formerly, these are heaters of various kinds, which are based on the principle of operation of the Joule-Lenz law. The power converted to heat is determined by the size of the resistance flowing by the current.
For domestic purposes, it is more convenient to maintain voltage. In addition to heaters, there are many other appliances. First of all, electronics. The voltage across the active resistance of the conductor is linearly dependent on the current. There is no difference what to keep constant. Why then during the welding process it is necessary to stabilize.
The welder’s hand is unable to move with sufficient hardness, the air fluctuations constantly change the arc length. There are other interferences. The voltage at the site is variable. Consequently, the current would change( according to Ohm’s law).It is unacceptable for the reasons described above: the temperature will change, the process will go the wrong way. It is necessary to maintain a constant current, not voltage.
How do practitioners get the current of a given form
Historically, galvanic current sources are the first to be discovered. It happened in 1800.The genius who gave humanity the first power source is Alessandro Volta. A galaxy of discoveries followed. The first gauge was a galvanometer, a device that records the strength of an electric current. The principle of action of the novelty, presented to the world by Schweiger, was based on the interaction of the magnetic fields of the conductor, the needle of the compass.
The question is important for a simple reason, to maintain the desired current law, you need to measure the physical quantity. The first galvanometers estimated the parameter by the strength of the magnetic field created by the conductor. Later laid the foundation for the action of the first testers. How does modern equipment work?
Chargers maintain a constant voltage. The current is measured in order to assess the fullness of the battery. Thanks to a thoughtful approach, the phone is able to signal mnemonically about the process. When the battery is full, the charging bar is completely painted over( the first cell phones), or disappears( on many smartphones off).The course of the process is recorded by the Hall sensor: only the pulses disappear, it is considered that the device does not need further recharging.
Based on this effect, it was possible at first to record the presence / absence of current. With the development of science, technology appeared converters based on indium compounds, differing in quite good metrological qualities. According to the output voltage capable of estimating the parameters of the current. Modern analog-to-digital measuring transducers will translate the potential difference into digits that the processor can understand. The latter performs the necessary operations to control the device, helping to obtain a current of a given shape.
Inverter acts in a similar way. Pulse sequences, cut with a key, pass a small-sized parameter unchanged( form of a graph), with changed characteristics. It remains only to measure the necessary quantities, to integrate at a certain site. As a result, a modern welding machine is by definition protected against sticking: with a sharp increase in the current, the power is turned off. Inverters have some other useful qualities provided by electronics. That is why welders like machines.
In high-power circuits, the current is controlled by transformers. Hall sensors with dozens, hundreds of amps do not work directly. A typical limit is tens of mA.The principle similar to that used in digital multimeters is used: some small part is separated from the flow moving along the electric circuit of charges. Further, the proportion is estimated by the total value. Current transformers act in a similar way. Not having a primary winding, by electromagnetic induction transfer a small part of the field energy to the measuring means( for example, a meter, monitoring equipment).
Distinctive features of
From the above, we understand the following:
- Physics means a unit that generates a constant parameter at the output as a current source. Practice often makes other demands. Although more often current is required constant.
- In the diagrams, the current source is designated differently than the EMF source. A circle with two jackdaws. Sometimes there is a Latin letter next to them. These things help, according to the Kirchhoff equations, to solve the problem of finding the conditions of the elements of an electrical circuit.
- The form of the law of the generated current is determined by the needs of the consumer. Most household appliances are powered by voltage. The constancy of the current, a special form is not needed, even bring harm. Mincer when wedging the shaft with a bone requires more energy. Regulatory and protective electronics are set up for this.
- The power delivered by an ideal source grows in proportion to the active load resistance. In reality, we see a certain limit, above which the parameters will start to differ from the given ones.
Simply put, historically, from a practical point of view, it is more convenient to maintain a constant voltage, not a current. The term considered by the section causes a lot of difficulties for people of outsiders, distant to electronics, who are well versed in technology. So, the current source is responsible for maintaining the desired form of current. Often requires constant.
The magnitude of the current will serve the purpose of regulation. Spark collector engine is accompanied by an increase in load. Current consumption increases, control circuits increase the voltage on the windings in order to overcome the “crisis” that has arisen. Leads to the need to control the current. In meat grinders, the task is solved by a feedback circuit that forms the cut-off angle with an input voltage key.
While trying to keep a potential difference constant, the devices vary the current consumption. As a result, the power requested from the substation changes, the effect leads to a subsidence of the voltage. Visually, we observe a slow flashing of the incandescent bulbs( the energy-saving ones carry a driver in the base to maintain constant voltage).Similarly, devices would show current sagging at a constant voltage.