A measuring current transformer is a device designed to control and measure voltage, current, phase of an electrical signal in a controlled circuit. It is used only in cases where it is not possible to use standard instruments to determine the magnitude of various indicators. This useful device can be bought at a relatively low price or made by hand.
General information
Before determining what a current transformer is for, it is necessary to study in detail its device, purpose, varieties and main advantages. All this information will help you choose the most efficient model for each specific installation.
Purpose and device
The instrument transformer is not used as often as other types of this device. This is due to its narrow focus, which allows you to perform the function assigned to it with the highest quality.
The purpose of the current transformer can be varied. Most often use devices of this type for the following purposes:
The current transformer device is distinguished by its simplicity and affordability. It can be easily understood not only by a highly qualified electrician, but also by a beginner. The device includes the following components:
- Closed core. It is a combined set of plates made of sheet electrical steel.
- Primary winding having a standard number of turns.
- One or two secondary windings.
Main settings
The technical characteristics of all measuring current transformers are described by several basic parameters. They must be indicated in the device passport or other attached documentation. According to these indicators, experts recommend choosing a model of the device that the master can install on a particular design. Main parameters:
- Rated voltage. The value of this indicator for each specific transformer model is indicated in the technical data sheet. Depending on the type of device, it can range from 0.66 to 1150 kV.
- Rated current of the primary winding. This important parameter can be found in technical documentation and literature. Some manufacturers indicate it in the passport. The current value depends on the version of the device and varies from 1 to 40 thousand amperes.
- Rated current in the secondary winding. Unlike the previous indicator, this one has standard values \u200b\u200b(1 or 5 amperes). Transformers that are made to order may have a parameter that will be equal to 2 or 2.5 A.
- Transformation ratio. It is a value showing the ratio of the current indicators in the primary and secondary windings. Professionals distinguish between 2 varieties of this coefficient (real and nominal) and use them in various calculations.
Advantages and disadvantages
In order to better understand the principle of operation and purpose of current transformers, it is necessary to consider all the advantages and disadvantages of this device. There are many more positive sides, so the devices are popular with consumers.
Despite a large number of advantages, instrument transformers have several disadvantages. They must be taken into account before buying a device and starting to use it. Otherwise, you may encounter various difficulties that will complicate the operation of the device and increase the likelihood of breakdowns.
Among the most significant shortcomings are the following:
- low sensitivity at low current;
- dependence of reading accuracy on external magnetic fields;
- high sensitivity to current fluctuations;
- high power consumption of the device itself.
Varieties of designs
Measuring current transformers are available in various types. All of them have the same purpose, but differ in their constituent elements and principle of operation. Each variety is used to achieve certain goals, which allows you to choose the best option for each case.
coil type
This type of instrument transformers is considered the simplest in design. He gained his popularity back in Soviet times, when there were no better and more efficient devices. The coil device consists of the following elements:
Such transformers are small in size and have an acceptable price, which is due to the possibility of mechanization of winding work. Despite this, the devices have several significant drawbacks that reduce their popularity among consumers.
These include:
- low discharge voltage, which is the result of weak coil insulation;
- the possibility of using only at low rated voltages (no more than 3 kV);
- the ability to work only with reduced requirements for electrical strength.
These devices are considered the most commonly used. They are widely used in various switchgears, designed for voltages from 6 to 35 kV. Their device is not particularly complex.
The design consists of the following parts:
- cast epoxy body;
- magnetic circuit;
- primary winding;
- secondary winding.
Transformers of this type are valued for making it possible to save a bushing in closed switchgear. Other advantages of the device include:
- small dimensions;
- high electrodynamic resistance.
Rod device
Rod transformers are often referred to as single-turn transformers. Their main feature is an increase in accuracy with an increase in current strength and a decrease - with a decrease. It is due to the fact that the primary winding passes through the core hole only once, which leads to the numerical equality of the number of ampere-turns and the rated current.
The device consists of the following parts:
- iron magnetic circuit (core);
- bushing rod;
- secondary and primary winding.
In rod current transformers, the cores can be round or rectangular. The length of the magnetic path will depend on this, which should have a certain value for each specific case. In most situations, experts recommend using round cores, which will reduce magnetic losses and increase the efficiency of the device.
Bus device
Tire transformers are products that include cores with a secondary winding, and there is no primary winding. A special hole is provided in the main insulation of the device, through which the switchgear bus is passed, which acts as the primary winding.
This kind of transformer is very similar to the rod one. Only at low voltage readings, several turns of the conductor are laid through the hole in the core, which makes it possible to obtain a multi-turn design of the device.
The main advantages of a busbar transformer are:
- simplicity of design;
- ease of installation, repair and maintenance work;
- the ability to use the device not only at low rated currents, but also at high (more than 2 thousand amperes);
- high electrodynamic resistance due to the stability of the busbar structure.
Wiring diagrams
In order for the device to work efficiently and perform its functions with high quality, you need to connect it correctly. To do this, you should be guided by one of the standard schemes that can satisfy the requirements of equipment owners. Only in this case it is possible to achieve the desired result and complete the work in the shortest possible time.
The main connection diagrams of transformers and relay windings:
Service Rules
In most cases, the service life of an instrument current transformer is about 20 years. To extend this period by 10 years or more, it is necessary to properly maintain the device and take preventive measures at the right time.
Primary requirements which must be observed to increase the service life of the transformer:
The measuring current transformer is a useful device that allows you to measure and regulate various system parameters. With the right choice of device, its installation and compliance with all the recommendations of professionals, you can extend the life of the device, as well as reduce the likelihood of any problems.
The transformer is an indispensable device in electrical engineering.
Without it, the energy system in its current form could not exist.
These elements are present in many electrical appliances.
Those who wish to get to know them better are invited to this article, the topic of which is a transformer: the principle of operation and types of devices, as well as their purpose.
This is the name of a device that changes the magnitude of an alternating electrical voltage. There are varieties that can change its frequency.
Many devices are equipped with such devices, they are also used independently.
For example, installations that increase the voltage to transmit current through electric mains.
They raise the voltage generated by the power plant to 35 - 750 kV, which gives a double benefit:
- losses in wires are reduced;
- smaller wires are required.
In urban power networks, the voltage is again reduced to a value of 6.1 kV, again using. In distribution networks that distribute electricity to consumers, the voltage is reduced to 0.4 kV (these are the usual 380 /).
Principle of operation
The operation of the transformer device is based on the phenomenon of electromagnetic induction, which consists in the following: when the parameters of the magnetic field crossing the conductor change, an EMF (electromotive force) arises in the latter. The conductor in the transformer is present in the form of a coil or winding, and the total EMF is equal to the sum of the EMF of each turn.
For normal operation, it is required to exclude electrical contact between the turns, therefore, a wire in an insulating sheath is used. This coil is called the secondary coil.
The magnetic field necessary to generate an EMF in the secondary coil is created by another coil. It is connected to a current source and is called primary. The operation of the primary coil is based on the fact that when a current flows through a conductor, an electromagnetic field is formed around it, and if it is wound into a coil, it is amplified.
How a transformer works
When flowing through the coil, the parameters of the electromagnetic field do not change and it is unable to induce an EMF in the secondary coil. Therefore, transformers work only with alternating voltage.
The nature of the voltage conversion is affected by the ratio of the number of turns in the windings - primary and secondary. It is denoted by "Kt" - the transformation ratio. The law applies:
Kt = W1 / W2 = U1 / U2,
- W1 and W2 - the number of turns in the primary and secondary windings;
- U1 and U2 are the voltage at their terminals.
Therefore, if there are more turns in the primary coil, then the voltage at the terminals of the secondary is lower. Such an apparatus is called a step-down, Kt it has more than one. If there are more turns in the secondary coil, the transformer raises the voltage and is called step-up. Its Kt is less than one.
Large power transformer
If losses are neglected (an ideal transformer), then from the law of conservation of energy it follows:
P1 = P2,
where P1 and P2 are the current power in the windings.
Because the P=U*I, we get:
- U1 * I1 = U2 * I2;
- I1 = I2 * (U2 / U1) = I2 / Kt.
It means:
- in the primary coil of the step-down device (Kt\u003e 1), a current of lesser strength flows than in the secondary circuit;
- with step-up transformers (Kt< 1) все наоборот: сила тока в первичной катушке выше, чем в цепи вторичной.
This circumstance is taken into account when selecting the cross-section of wires for the windings of the apparatus.
Design
Transformer windings are put on a magnetic circuit - a part made of ferromagnetic, transformer or other soft magnetic steel. It serves as a conductor of the electromagnetic field from the primary coil to the secondary.
Under the influence of an alternating magnetic field, currents are also generated in the magnetic circuit - they are called eddy currents. These currents lead to energy losses and heating of the magnetic circuit. The latter, in order to minimize this phenomenon, is recruited from a plurality of plates isolated from each other.
Coils are placed on the magnetic circuit in two ways:
- near;
- wrap one over the other.
Windings for microtransformers are made of foil with a thickness of 20 - 30 microns. Its surface, as a result of oxidation, becomes a dielectric and plays the role of insulation.
Transformer design
In practice, it is impossible to achieve the ratio P1 = P2 due to three types of losses:
- dispersion of the magnetic field;
- heating of wires and magnetic circuit;
- hysteresis.
Hysteresis losses are the energy costs for remagnetization of the magnetic circuit. The direction of the electromagnetic field lines is constantly changing. Each time it is necessary to overcome the resistance of the dipoles in the structure of the magnetic circuit, which lined up in a certain way in the previous phase.
Hysteresis losses tend to be reduced by using different designs of magnetic circuits.
So, in reality, the values of P1 and P2 are different and the ratio P2 / P1 is called the efficiency of the device. To measure it, the following transformer operating modes are used:
- idle move;
- short-circuited;
- with load.
In some types of transformers operating with high frequency voltage, there is no magnetic circuit.
Idle mode
The primary winding is connected to a current source, and the secondary circuit is open. With this connection, no-load current flows in the coil, mainly representing the reactive magnetizing current.
This mode allows you to define:
- device efficiency;
- transformation ratio;
- losses in the magnetic circuit (in the language of professionals - losses in steel).
Transformer diagram in idle mode
Short circuit mode
The outputs of the secondary winding are closed without load (short-circuit), so that the current in the circuit is limited only by its resistance. A voltage is applied to the contacts of the primary so that the current in the secondary winding circuit does not exceed the rated current.
This connection allows you to determine the heating losses of the windings (losses in copper). This is necessary when implementing circuits using an active resistance instead of a real transformer.
Loaded mode
In this state, a consumer is connected to the terminals of the secondary winding.
Cooling
The transformer heats up during operation.
There are three cooling methods:
- natural: for low-power models;
- forced air (fan blowing): medium power models;
- powerful transformers are cooled with a liquid (mainly oil is used).
Oil cooled instrument
Types of transformers
Devices are classified by purpose, type of magnetic circuit and power.
Power transformers
The largest group. It includes all transformers operating in the power grid.
Autotransformer
This type has an electrical contact between the primary and secondary windings. When winding the wires, several conclusions are made - when switching between them, a different number of turns is used, which changes the transformation ratio.- Increased efficiency. This is explained by the fact that only a part of the power is converted. This is especially important when there is little difference between input and output voltage.
- Low cost. This is due to the lower consumption of steel and copper (the autotransformer has a compact size).
It is advantageous to use these devices in networks with a voltage of 110 kV or more with effective grounding at Kt not higher than 3-4.
Current transformer
Used to reduce the current strength in the primary winding connected to the power source. The device is used in protective, measuring, signaling and control systems. The advantage in comparison with shunt measurement circuits is the presence of galvanic isolation (no electrical contact between the windings).
The primary coil is connected to an alternating current circuit - investigated or controlled - with a load in series. An executive indicator device, for example, a relay, or a measuring device is connected to the terminals of the secondary winding.
Current transformer
The permissible resistance in the secondary coil circuit is limited to meager values - almost a short circuit. For most current coils, the rated current in this coil is 1 or 5 A. When the circuit is opened, a high voltage is generated in it that can break through the insulation and damage the connected devices.
pulse transformer
It works with short pulses, the duration of which is measured in tens of microseconds. The shape of the pulse is practically not distorted. Mainly used in video systems.
welding transformer
This device:
- lowers the voltage;
- designed for rated current in the secondary circuit up to thousands of amperes.
You can regulate the welding current by changing the number of turns of the windings involved in the process (they have several leads). In this case, the value of the inductive reactance or the secondary open circuit voltage changes. By means of additional conclusions, the windings are divided into sections, therefore the adjustment of the welding current is carried out in steps.
The dimensions of the transformer largely depend on the frequency of the alternating current. The higher it is, the more compact the device will turn out.
Welding transformer TDM 70-460
The device of modern inverter welding machines is based on this principle. In them, alternating current is processed before being fed to the transformer:
- rectified by a diode bridge;
- in the inverter - a microprocessor-controlled electronic unit with fast switching key transistors - becomes variable again, but at a frequency of 60 - 80 kHz.
Because these welding machines are so light and small.
There are also pulse-type power supplies, for example, in a PC.
Isolating transformer
In this device, galvanic isolation is necessarily present (there is no electrical contact between the primary and secondary windings), and Kt is equal to one. That is, the isolation transformer leaves the voltage unchanged. It is necessary to improve the security of the connection.
Touching live parts of equipment connected to the network through such a transformer will not result in a strong electric shock.
In everyday life, this method of connecting electrical appliances is appropriate in wet rooms - in bathrooms, etc.
In addition to power transformers, there are signal separators. They are installed in electrical circuits for galvanic isolation.
Magnetic circuits
There are three types:
- Rod. Made in the form of a stepped rod. Characteristics leave much to be desired, but are simple in execution.
- Armored. Better rod conduct a magnetic field and in addition protect the windings from mechanical stress. Disadvantage: high cost (requires a lot of steel).
- Toroidal. The most effective variety: they create a homogeneous concentrated magnetic field, which helps to reduce losses. Transformers with a toroidal magnetic circuit have the highest efficiency, but they are expensive due to the complexity of manufacturing.
Power
Power is usually expressed in volt-amperes (VA). On this basis, devices are classified as follows:- low power: less than 100 VA;
- medium power: several hundred VA;
There are installations of high power, measured in thousands of VA.
Transformers differ in purpose and characteristics, but their principle of operation is the same: an alternating magnetic field generated by one winding excites an EMF in the second, the value of which depends on the number of turns.
The need for voltage conversion arises very often, because transformers are most widely used. This device can be made independently.
Current transformer (CT) - a static electromagnetic device, where the primary winding is connected to a power source, and the second - to measuring or protective devices with low resistance. Converters are widely used to measure the magnitude of the current and in units of relay protection of power systems. They provide complete safety for measurements in high-voltage lines.
During the operation of the current transformer, the secondary winding is always under load, the resistance of which is regulated by the requirements for the accuracy of the transformation ratio. A slight deviation of the resistance from the device indicated in the passport is allowed.
If there is an increase in load, then the voltage in the second winding will increase sharply, which can lead to breakdown of the insulation and damage to the device. This situation creates a safety hazard for employees who service the electrical appliance. The current transformer device includes:
- base;
- magnetic circuit (core);
- primary winding;
- secondary winding;
- terminal block for connecting the cable from the power source;
- ground contact.
The primary winding is made in the form of a coil mounted on a magnetic circuit, or as a busbar. According to the design, some devices do not have a built-in primary coil, but it is supplemented by service personnel by connecting a separate wire through a special window.
The case of the device performs the role of insulation and protection of the windings from external damage. In the latest models of devices, the cores are made of nanocrystalline alloys, which significantly increase the accuracy class of the device.
Due to the large losses in the core, the device begins to heat up strongly, which leads to wear or failure of its insulation. The second winding in the open state also creates a negative phenomenon, as overheating and burnout of the magnetic wire occurs.
The main characteristic of the device is the transformation ratio, which indicates the ratio of the rated current in the primary winding to the same value in the secondary. The real value of this coefficient is somewhat different from the nominal, which is explained by the degree of instrument error.
This is due to the fact that in magnetic structures there are losses associated with magnetization and heating of the magnetic circuit. To somewhat smooth out these errors, manufacturers use a turn correction.
Purpose of the device
According to their purpose, current transformers are special auxiliary devices used in combination with various measuring equipment and protective mechanisms in AC networks.
The principle of operation of the current transformer is the transformation of any values that acquire more perceptible values in order to obtain information and provide power to protective relays. Thanks to the isolation of the devices, the employees of the service organization are reliably protected from electric shock. All types of transformers can serve two functions:
- Measuring current in a circuit- with their help, data is transmitted to measuring devices that are connected to the secondary winding. In this case, the transformer can convert the high current into more acceptable parameters.
- Safety actions- devices primarily transmit data to protective devices and control devices. With the help of transformers, electrical indicators are converted to power relay equipment.
According to their purpose and principle of operation, current transformers contribute to the connection of measuring instruments to high voltage power lines when it is not possible to connect them directly. They are needed to transfer the readings taken to the measurement equipment, which is connected to the secondary winding.
In addition, the converters monitor the state of the electric current in the circuit to which they are connected. When connected to power automatic protection, the device monitors networks, the presence and condition of grounding. If the current reaches the maximum value, then protection automatically turns on and the operation of all equipment stops.
Operating principle
The current transformer works on the basis of the law of electromagnetic induction. From an external power source, voltage is supplied to the terminals of the device, which are directly connected to the primary winding, which has a specific number of turns. As a result, a magnetic flux is formed around the coil, which traps the core.
Due to this, the loss of readings during the conversion will be negligible. When the current crosses the secondary winding, the magnetic flux activates an electromotive force, under the influence of which the resistance of the coil and the load at the output are overcome.
In parallel with this process, there is a decrease in voltage from the secondary winding. If a short circuit occurs in the secondary winding or a load is connected to it, then under the influence of an electromotive force, it is possible to determine the secondary current in it.
Instrument classification
All types of units are classified depending on the design and what technical indicators they have. In addition to measuring and protective transformers, there are intermediate types of these converters. In this case, the device is connected for measurement to the relay protection circuit.
Laboratory types of transducers are distinguished, which have increased measurement accuracy and a variety of transformation ratios. Current transformers are divided into:
From how the converter is arranged, it can have one or two stages. The operating voltage of the devices is in the range up to 1 thousand V and above. All necessary technical data have alphabetic, numeric designations and are present on the corresponding tags.
Popular Models
Any manufactured brand of the device has separate parameters and technical characteristics. Domestic manufacturers produce a large number of these devices. These include:
Three-phase devices are connected to the network in a "triangle" or "star". In the first case, it is possible to obtain a large current value in the secondary winding, and in the second case, it is possible to track the current value in each phase.
In today's material, I decided to start considering issues related to the basics of the theory of current transformers. These devices themselves are ubiquitous in electrical installations, and I think it will be interesting and useful for everyone to renew in memory the principle of their operation.
Purpose of current transformers: current conversion and circuit separation
Let's start by answering the question - what is a current transformer for? There are several main issues that the installation of current transformers solves.
- Firstly, this is the measurement of large currents, when it is not possible to directly measure the real value of the primary current. The value converted down after the current transformer is measured. Usually it is 1, 5 or 10 amps.
- Secondly, this is the separation of primary and secondary circuits. Thus, the insulation of relay equipment, electricity meters, and measuring instruments is protected.
What does TT consist of, the principle of its operation
The current transformer has a closed core (magnetic circuit), which is assembled from sheets of electrical steel. There are two windings on the core: primary and secondary.
The primary winding is connected in series (in a cut) of the circuit through which the measured (primary) current flows. Series-connected relays and devices are connected to the secondary winding, which form the secondary load of the current transformer. Such a description of the composition of the current transformer is sufficient to describe the principle of its operation, a more detailed description of the actual composition of the current transformer is given in another article.
To consider the principle of operation of a current transformer, consider the circuit located in the figure.
Current I 1 flows in the primary winding, creating a magnetic flux Ф 1. Variable magnetic flux Ф 1 crosses both windings W 1 and W 2 . When crossing the secondary winding, the flux F 1 induces an electromotive force E 2, which creates a secondary current I 2 . Current I 2 , according to Lenz's law, has a direction opposite to the direction of I 1 . The secondary current creates a magnetic flux Ф 2 , which is directed oppositely Ф 1 . As a result of the addition of magnetic fluxes F 1 and F 2, the resulting magnetic flux is formed (in the figure it is designated F us). This flow is a few percent of the F 1 flow. It is the flow F to us that is the link that produces the transfer and transformation of the current. It is called the flux of magnetization.
Ideal CT transformation ratio
In the primary winding w 1, a magnetomotive force F 1 \u003d w 1 * I 1 is created, and in the secondary - F 2 \u003d w 2 * I 2. If we assume that there are no losses in the current transformer, then the magnetomotive forces are equal in magnitude, but opposite in sign. F 1 \u003d -F 2. As a result, we get that I 1 /I 2 =w 2 /w 1 =n. This ratio is called the transformation ratio of the current transformer.
Real CT transformation ratio
In a real current transformer, there are energy losses. These losses go to:
- creation of a magnetic flux in a magnetic circuit
- heating and magnetization reversal of the magnetic circuit
- heating of secondary winding wires and circuit
To the magnetomotive forces from the previous paragraph, the magnetization mfs Fus = Ius * w1 will be added. In the expression below, currents and mfs are vectors. F 1 \u003d F 2 + F to us or I 1 * w 1 \u003d I 2 * w 2 + I to us * w 1 or I 1 \u003d I 2 * (w 2 / w 1) + I to us
In normal mode, when the primary current does not exceed the rated current of the current transformer, the current value Ius does not exceed 1-3 percent of the primary current, and this value can be neglected. Under abnormal conditions, the so-called magnetizing current surge occurs, you can read more about this here. It follows from the formula that the primary current is divided into two circuits - the magnetization circuit and the load circuit. Learn more about the CT equivalent circuit and the CT vector diagram.
Operating modes of current transformers
TT has two main modes of operation - steady state and transient.
In the steady state of operation, the currents in the primary and secondary windings do not contain free aperiodic and periodic components. In the transient mode, free damped current components pass through the primary and secondary windings.
If the CT is chosen correctly, then in both operating modes the errors should not exceed the allowable in these modes, and the currents in the windings should not exceed the allowable thermal and dynamic resistance.
CTs for measurements are provided for operation in steady state, provided that the permissible errors are not exceeded. The operation of the CT for protection begins from the moment the overload current or short-circuit current occurs, in these modes the requirements of certain types of protection must be met.
What is the difference between a current transformer and a voltage transformer and a power transformer
There are significant differences in the operation of TT and TN.
Firstly, the primary current of the CT is independent of the secondary load, which is typical of a VT. This is determined by the fact that the resistance of the CT secondary winding is an order of magnitude less than the resistance of the primary circuit. In voltage transformers and power transformers, the primary current depends on the magnitude of the secondary load current.
Secondly, the CT always works with a closed secondary winding and the value of its secondary load resistance does not change during operation.
Thirdly, the operation of a CT with an open secondary winding is not allowed; for VTs and power transformers, when the secondary winding is opened, a transition to the idle operation mode occurs.
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Maybe someone thinks that a transformer is something between a transformer and a terminator. This article is intended to destroy such ideas.
A transformer is a static electromagnetic device designed to convert an alternating electric current of one voltage and a certain frequency into an electric current of another voltage and the same frequency.
The work of any transformer is based on the phenomenon of electromagnetic inductiondiscovered by Faraday.
Purpose of transformers
Different types of transformers are used in almost all power supply circuits for electrical appliances and in the transmission of electricity over long distances.
Power plants generate a current of relatively low voltage - 220 , 380 , 660 B. Transformers, increasing the voltage to values of the order thousand kilovolts, can significantly reduce losses in the transmission of electricity over long distances, and at the same time reduce the cross-sectional area of power transmission lines.
Just before getting to the consumer (for example, to a regular home outlet), the current passes through a step-down transformer. This is how we get our usual 220 Volt.
The most common type of transformer is power transformers . They are designed to convert voltage in electrical circuits. In addition to power transformers, various electronic devices use:
- pulse transformers;
- power transformers;
- current transformers.
The principle of operation of the transformer
Transformers are single-phase and multi-phase, with one, two or more windings. Consider the scheme and principle of operation of the transformer using the example of the simplest single-phase transformer.
What is a transformer made of? In the simplest case, from one metal core and two windings . The windings are not electrically connected to each other and are insulated wires.
One winding (it is called primary ) is connected to an AC power source. The second winding is called secondary , is connected to the final consumer of current.
When a transformer is connected to an AC source, an alternating current flows in the turns of its primary winding. I1 . This creates a magnetic flux F , which permeates both windings and induces an emf in them.
It happens that the secondary winding is not under load. This mode of operation of the transformer is called idle mode. Accordingly, if the secondary winding is connected to any consumer, a current flows through it I2 , arising under the influence of EMF.
The magnitude of the EMF that occurs in the windings directly depends on the number of turns of each winding. The ratio of the EMF induced in the primary and secondary windings is called the transformation ratio and is equal to the ratio of the number of turns of the respective windings.
By selecting the number of turns on the windings, it is possible to increase or decrease the voltage on the current consumer from the secondary winding.
Ideal Transformer
An ideal transformer is a transformer in which there is no energy loss. In such a transformer, the current energy in the primary winding is completely converted first into the energy of the magnetic field, and then into the energy of the secondary winding.
Of course, such a transformer does not exist in nature. Nevertheless, in the case when heat losses can be neglected, it is convenient to use the formula for an ideal transformer in calculations, according to which the current powers in the primary and secondary windings are equal.
By the way! For our readers there is now a 10% discount on any kind of work
Energy losses in the transformer
The efficiency of transformers is quite high. However, energy losses occur in the winding and core, causing the temperature to rise during transformer operation. For transformers of small power, this is not a problem, and all the heat goes into the environment - natural air cooling is used. Such transformers are called dry.
In more powerful transformers, air cooling is not enough, and oil cooling is used. In this case, the transformer is placed in a mineral oil tank through which heat is transferred to the tank walls and dissipated into the environment. In high-power transformers, exhaust pipes are additionally used - if the oil boils, the resulting gases need an outlet.
Of course, transformers are not as simple as it might seem at first glance - after all, we briefly reviewed the principle of the transformer. An electrical engineering test with transformer calculation tasks can suddenly become a real problem. A special student service is always ready to help in solving any problems with your studies! Contact Zaochnik and learn easily!
