The Importance of Power Transformers

June 12, 2018 | Author: jinmenchie | Category: Transformer, Inductor, Alternating Current, Electric Current, Electric Power Distribution



The Importance Of Power TransformersElectricity and Energy has become an important part of everyday life, and without electricity we can not imagine life today. Most of the appliances work. We are facing various problems due to voltage fluctuations. Sometimes, our equipment malfunctions due to voltage problems. The solution to all these problems can be corrected only by a processor. Power transformers and transformer is an electronic device that is used to change alternating current from one circuit to another by electromagnetic induction. These adapters will work in different mechanisms to reduce the input voltage or increase the voltage of electrical equipment. These transformers have two or more windings wounded on laminated iron core and the number of windings is based on the requirement for voltage, the transformer is used to provide. There are several types of transformers as a separate transformer, transformers, electric transformer, audio transformer, power transformer, high voltage transformers and low voltage, to intensify and step- down transformers, etc. Each of these forms have their own properties and uses of the transfer voltage based unit is attached with. Electrical transformer is a device that is used to increase or decrease the voltage of alternating current or voltage. Transformers are two groups of coils are called primary and secondary coils associated with some magnetic fields, which act as conductors. This issue of the number of windings of the transformer operation. There are various forms, such as electrical transformers to step up transformers increase the voltage or step down transformers to lower voltage levels, which can be used for power lines and household appliances to adjust the power supply and reduce the cost of the bill. Current transformers are used for secondary or complementary to the current produces a power transformer, and this will help our customers get a lot of power for their various applications, such as metering and protective relaying in the electrical security measure for large currents up to high voltages. Audio transformers are designed for epoxy resin, which facilitates improvements in audio quality by removing the distracting sound signals from other devices. Flyback transformers for converting the input voltage and current output voltage and current transformers provided, and these are available in different models and sizes. The electrical contacts are electrical components that are used to stop the flow of electricity by interrupting the current or away from one leader to another. These electrical contacts are available for medium current, high voltage and low current devices. The circuit breaker is an electrical switch that operates automatically to turn off or interrupt a circuit damage due to high voltage. This is used to detect critical defects in the mechanism of the circuit and power outage to prevent the repair of equipment. These switches are of different types, such as vacuum circuit breakers, SF6 circuit breakers, switches installed patches, etc. Transformer, a device that transfers electric energy from one circuit to another, usually with a change in voltage. Transformers work only with a varying electric current, such as alternating current (AC). Transformers are important in the distribution of electric power. They raise the voltage of the electricity generated at a power plant to the high levels needed to transmit the electricity efficiently. Other transformers reduce the voltage at the locations where the electricity is used. Many household devices contain transformers to raise or lower house-current voltage as needed. Television sets and stereo equipment, for example, require high voltages; doorbells and thermostats, low voltages. How A Transformer Works A simple transformer consists essentially of two coils of insulated wire. In most transformers, the wires are wound around an iron-containing structure called the core. One coil, called the primary, is connected to a source of alternating current that produces a constantly varying magnetic field around the coil. The varying magnetic field, in turn, produces an alternating current in the other coil. This coil, called the secondary, is connected to a separate electric circuit. The ratio of the number of turns in the primary coil to the number of turns in the secondary coil—the turns ratio— determines the ratio of the voltages in the two coils. For example, if there is one turn in the primary and ten turns in the secondary coil, the voltage in the secondary coil will be 10 times that in the primary. Such a transformer is called a step-up transformer. If there are ten turns in the primary coil and one turn in the secondary the voltage in the secondary will be one-tenth that in the primary. This kind of transformer is called a step-down transformer. The ratio of the electric current strength, or amperage, in the two coils is in inverse proportion to the ratio of the voltages; thus the electrical power (voltage multiplied by amperage) is the same in both coils. The impedance (resistance to the flow of an alternating current) of the primary coil depends on the impedance of the secondary circuit and the turns ratio. With the proper turns ratio, the transformer can, in effect, match the impedances of the two circuits. Matched impedances are important in stereo systems and other electronic systems because they permit the maximum amount of electric power to be delivered from one component to another. In an autotransformer, there is only one coil and both circuits are connected to it. They are connected at different points, so that one circuit contains a larger portion of the coil (that is, has more turns) than the other. Electrical Transformers Explained  Electrical Transformers On-line Directory  Electrical Transformers "Request For Quotation" Service  Electrical Transformers Repair & Services "Request For Quotation" Electrical transformers are used to "transform" voltage from one level to another, usually from a higher voltage to a lower voltage. They do this by applying the principle of magnetic induction between coils to convert voltage and/or current levels. In this way, electrical transformers are a passive device which transforms alternating current (otherwise known as "AC") electric energy from one circuit into another through electromagnetic induction. An electrical transformer normally consists of a ferromagnetic core and two or more coils called "windings". A changing current in the primary winding creates an alternating magnetic field in the core. In turn, the core multiplies this field and couples the most of the flux through the secondary tranformer windings. This in turn induces alternating voltage (or emf) in each of the secondary coils. Electrical transformers can be configured as either a single-phase or a three-phase configuration. There are several important specifications to specify when searching for electrical transformers. These include: maximum secondary voltage rating, maximum secondary current rating, maximum power rating, and output type. An electrical transformer may provide more than one secondary voltage value. The Rated Power is the sum of the VA (Volts x Amps) for all of the secondary windings. Output choices include AC or DC. For Alternating Current waveform output, voltage the values are typically given in RMS values. Consult manufacturer for waveform options. For direct current secondary voltage output, consult manufacturer for type of rectification. Cores can be constructed as either a toroidal or laminated. Toroidal units typically have copper wire wrapped around a cylindrical core so the magnetic flux, which occurs within the coil, doesn't leak out, the coil efficiency is good, and the magnetic flux has little influence on other components. Laminated refers to the laminated-steel cores. These steel laminations are insulated with a nonconducting material, such as varnish, and then formed into a core that reduce electrical losses. There are many types. These include autotransformer, control, current, distribution, general-purpose, instrument, isolation, potential (voltage), power, step-up, and step-down. Mountings include chassis mount, dish or disk mount, enclosure or free standing, h frame, and PCB mount. broadgage Senior Member Join Date May 2008 Location London, England Posts 740 For most single phase transformers, polarity is unimportant, all that matters is that the turns ratio must be correct for the intended application (plus of course suitable power rating and design) For a 3 phase transformer intended to work on its own, polarity is umimportant. For a 3 phase transformer to work in parralell with one or more other transformers, then polarity is important. Transformers of differing polarity wont work in parralell, no matter what alterations may be made to the external connections. A 3 phase transformer intended to supply utilisation voltages normally has only 4 output terminals, one for each phase, and a fourth terminal for the neutral, intended to supply 3 phase, 4 wire. There will be 3 windings inside the transformer, with one end of each winding connected together internaly to give the neutral. If two otherwise identical transformers are manufactured, one with the bottom ends of each winding connected together, and the other one with the top ends connected together, then these transformers are said to have opposite polarity. Each of them will work just fine on its own and provide a standard 3 phase, 4 wire service, but they will never work together. It would be possible to build a 3 phase transformer with each end of each low voltage winding connected to a terminal, 6 terminals in total. Such a transformer could be connected with either polarity, by altering the external connections. This is not usual in practice as it adds to costs. All British Standard transformers are built with the same polarity, and I would presume that similar standards exist in other countries. Why are transformers important? Answered Most RecentlySakshi Chaudhary Transformers can convert power at one voltage into power at another voltage. Electrical power needs to be at a high voltage for transmission over distances, but must be transformed to a lower voltage for use in the home. Transformer is an electrical device that makes the transfer of energy by forming inductive coupling between the winding of its circuits. Transformers are basically of two type's i.e; Step up transformer and step down transformer. Sue the varying current flowing through the primary winding creates a magnetic flux inside the core of the transformer and in secondary winding. A varying emf is produced in the secondary winding as a result of magnetic flux. The major usage of transformer is to either to vary relative voltage of the circuit or isolate it. Explaining Different Types of Transformers Transformers A transformer is an electrical device which, by the principles of electromagnetic induction, transfers electrical energy from one electric circuit to another, without changing the frequency. The energy transfer usually takes place with a change of voltage and current. Transformers either increases or decreases AC voltage. Transformers are used to meet a wide variety of needs. Some transformers can be several stories high, like the type found at a generating station or small enough to hold in your hand, which might be used with the charging cradle for a video camera. No matter what the shape or size, a transformers purpose remains the same: transforming electrical power from one type to another. There are many different types of transformers in use today. This resource will take a closer look at Power Transformers, Auto Transformers, Distribution Transformers, Instrument Transformers, Isolation Transformers, Potential Transformers and Current Transformers. How Transformers Work Transformer Configurations Power Transformer Distribution Transformer Autotransformer Isolation Transformer Instrument Transformer Current Transformer Potential Transformer Transformer Video Overview How Transformers Work. It is important to remember that transformers do not generate electrical power; they transfer electrical power from one AC circuit to another using magnetic coupling. The core of the transformer is used to provide a controlled path for the magnetic flux generated in the transformer by the current flowing through the windings, which are also known as coils. There are four primary parts to the basic transformer. The parts include the Input Connection, the Output Connection, the Windings or Coils and the Core.  Input Connections - The input side of a transformer is called the primary side because the main electrical power to be changed is connected at this point.  Output Connections - The output side or secondary side of the transformer is where the electrical power is sent to the load. Depending on the requirement of the load, the incoming electric power is either increased or decreased.  Winding - Transformers have two windings, being the primary winding and the secondary winding. The primary winding is the coil that draws power from the source. The secondary winding is the coil that delivers the energy at the transformed or changed voltage to the load. Usually, these two coils are subdivided into several coils in order to reduce the creation of flux.  Core - The transformer core is used to provide a controlled path for the magnetic flux generated in the transformer. The core is generally not a solid bar of steel, rather a construction of many thin laminated steel sheets or layers. This construction is used to help eliminate and reduce heating. Transformers generally have one of two types of cores: Core Type and Shell Type. These two types are distinguished from each other by the manner in which the primary and secondary coils are place around the steel core. o Core type - With this type, the windings surround the laminated core. o Shell type - With this type, the windings are surrounded by the laminated core. When an input voltage is applied to the primary winding, alternating current starts to flow in the primary winding. As the current flows, a changing magnetic field is set up in the transformer core. As this magnetic field cuts across the secondary winding, alternating voltage is produced in the secondary winding. The ratio between the number of actual turns of wire in each coil is the key in determining the type of transformer and what the output voltage will be. The ratio between output voltage and input voltage is the same as the ratio of the number of turns between the two windings. A transformers output voltage is greater than the input voltage if the secondary winding has more turns of wire than the primary winding. The output voltage is stepped up, and considered to be a "step-up transformer". If the secondary winding has fewer turns than the primary winding, the output voltage is lower. This is a "step-down transformer". Transformer Configurations. There are different configurations for both single-phase and three-phase systems.  Single-phase Power - Single-phase transformers are often used to supply power for residential lighting, receptacle, air-conditioning, and heating needs. Single phase transformers can be made even more versatile by having both the primary winding and secondary winding made in two equal parts. The two parts of either winding can then be reconnected in series or parallel configurations.  Three-phase Power - Power may be supplied through a three-phase circuit containing transformers in which a set of three single-phase transformers is used, or on three-phase transformer is used. When a considerable amount of power is involved in the transformation of three-phase power, it is more economical to use a three-phase transformer. The unique arrangement of the windings and core saves a lot of iron.  Delta and Wye Defined - There are two connection configurations for three-phase power: Delta and Wye. Delta and Wye are Greek letters that represent the way the conductors on the transformers are configured. In a delta connection, the three conductors are connected end to end in a triangle or delta shape. For a wye, all the conductors radiate from the center, meaning they are connected at one common point.  Three-phase Transformers - Three-phase transformers have six windings; three primary and three secondary. The six windings are connected by the manufacturer as either delta or wye. As previously stated, the primary windings and secondary windings may each be connected in a delta or wye configuration. They do not have to be connected in the same configuration in the same transformer. The actual connection configurations used depend upon the application. Power Transformer. A power transformer is used primarily to couple electrical energy from a power supply line to a circuit system, or to one or more components of the system. A power transformer used with solid state circuits is called a rectifier transformer. A power transformer's rating is given in terms of the secondary's maximum voltage and current-delivering capacity. Distribution Transformer. A pole-type distribution transformer is used to supply relatively small amounts of power to residences. It is used at the end of the electrical utility's delivery system. Autotransformer. The autotransformer is a special type of power transformer. It consists of a single, continuous winding that is tapped on one side to provide either a step-up or a step-down function. This is different from a conventional two-winding transformer, which has the primary and secondary completely isolated from each other, but magnetically linked by a common core. The autotransformer's windings are both electrically and magnetically interconnected. An autotransformer is initially cheaper than a similarly-rated two-winding transformer. It also has better regulation (smaller voltage drops), and greater efficiency. Furthermore, it can be used to obtain the neutral wire of a three-wire 240/120-volt service, just like the secondary of a two0winding transformer. The autotransformer is considered unsafe for use on ordinary distribution circuits. This is because the high-voltage primary circuits are connected directly to the low-voltage secondary circuit. Isolation Transformer. An isolation transformer is a very unique transformer. It has a 1:1 turn's ratio. Therefore, it does not step voltage up or down. Instead, it serves as a safety device. It is used to isolate the grounded conductor of a power line from the chassis or any portion of a circuit load. Using an isolation transformer does not reduce the danger or shock if contact is made across the transformer's secondary winding. Technically, any true transformer, whether used to transfer signals or power, is isolating, as the primary and secondary are not connected by conductors but only by induction. However, only transformers whose primary purpose is to isolate circuits (opposed to the more common transformer function of voltage conversion), are routinely described as isolation transformers. Instrument Transformer. For measuring high values of current or voltage, it is desirable to use standard low-range measuring instruments together with specially-constructed instrument transformers, also called accurate ratio transformers. An accurate ratio transformer does just as the name suggests. It transforms at an accurate ratio to allow an attached instrument to gauge the current or voltage without actually running full power through the instrument. It is required to transform relatively small amounts of power because it's only load, called a burden, is the delicate moving elements of an ammeter, voltmeter or wattmeter. There are two types of instrument transformers: 1. Current - Used with an ammeter to measure current in AC voltages 2. Potential - Used with a voltmeter to measure voltage (potential difference) in AC. Current Transformer. Current Transformers are a type of instrument transformers. They are used for the measurement of electric currents. A current transformer has a primary coil of one or more turns of heavy wire. It is always connected in series in the circuit in which current is to be measured. The secondary coil is made up of many turns of fine wire, which must always be connected across the ammeter terminals. The secondary of a current transformer must never be open-circuited. This is because the primary is not connected to a constant source. There is a wide range of possible primary voltages, because the device can be connected to many types of conductors. The secondary must always be available (closed-circuited) to react with the primary, to prevent the core from becoming completely magnetized. If this happens, the instruments will no longer read accurately. A clamp-on ammeter works in a similar way. By opening the clamp and placing it around a current carrying conductor, the conductor itself acts as a single turn primary. The secondary and the ammeter are conveniently mounted in the handle of the device. The dial allows a number of current ranges to be gauged accurately. Potential Transformer. A potential transformer is a carefully designed, extremely accurate step-down transformer. It is normally used with a standard 120-volt voltmeter. By multiplying the reading on the voltmeter (called the deflections) by the ratio of transformation, the user can determine the voltage on the high side. Common transformation ratios are 10:1, 20:1, 40:1, 80:1, 100:1, 120:1, and even higher. In general, a potential transformer is very similar to a standard two-winding transformer, except that it handles a very small amount of power. Transformers for this service are always the shell type, because this construction has been proven to provide better accuracy. Potential Transformers (like the one pictured above) are designed for monitoring single-phase and three-phase power line voltages in power metering applications. Single Phase Transformers Information Single phase transformers are designed to supply electric power to single-phase systems. These electrical devices transfer energy from one circuit to another via electromagnetic induction. Single phase power usually includes one hot lead and a grounded return line or neutral. Single phase electrical distribution is used mainly in residential and commercial applications, typically for lighting and heating. Single phase transformers carry many product specifications, including transformer type, winding turns, cooling method, core type, output voltage, and mounting or form factor. Performance specifications, approvals, and features are also important parameters to consider. Types of Single Phase Transformers There are many types of single phase transformers. Products include audio, balun, buck-boost, constant voltage (CVT), constant current, distribution, flyback (FBT), generator step-up (GSU), harmonic mitigating, high frequency, high voltage, impedance matching, and industrial control transformers. Categories of single phase transformers also include interface, inverter, isolation, leakage, lighting, medical, multi-ratio, neutral grounding, power, rectifier, resonant, solar power, and substation transformers. Autotransformers and variac or variable autotransformers are also available from single phase transformer suppliers. Like other types of transformers, single phase transformers may be used to increase or decrease the voltage from one side of the transformer to the other. The turn ratio or number of windings on the primary and secondary sides of the device determines the change in voltage. Step-up transformers produce a secondary voltage that is larger than the primary voltage. Step-down transformers have a secondary voltage that is smaller than the primary voltage. Variable single phase transformers are devices with a setting for changing the turn ratio as needed. One-to-one transformers are single phase transformers with a turn ratio of 1:1 or near 1:1. Product Specifications Cooling method, core type, output voltage, and mounting or form factor are additional product specifications to consider when selecting single phase transformers. There are four choices for cooling method: dry-type or air cooled, oil filled, water cooled, and other. Core types are listed as laminated, split, toroidal, and other. The output voltage is either alternating current (AC) or direct current (DC). There are many mounting or form factor styles for single phase transformers. Choices include chassis mount, chip transformer, dish or disk, H-frame, modular jack, pad mounted, printed circuit board (PCB), and pole mounted. Selecting Single Phase Transformers Selecting single phase transformers requires an analysis of performance specifications (including the single-phase primary configuration) as well as compliance with regulatory standards. Performance specifications include operating frequency range, maximum primary voltage rating, maximum secondary voltage rating, maximum secondary current rating, power rating and operating temperature. The single-phase primary configuration is listed as single, dual, quad (2+2) 5-lead, ladder, or other. In terms of regulatory standards, single phase transformers that are sold in Europe must be RoHS and WEEE compliant. ransformers Transformers are the basic and most widely used elements of electrical systems, and they play a particularly important role in the electrical power system. Transformer production in Croatia has a long tradition, and today there are three big and successful transformer factories in Končar Group: Končar – Power Transformers Ltd., Končar – Distribution and Special Transformers Inc., and Končar – Instrument transformers Inc. The successfulness of these factories is proven on the world market, and to keep and improve their market position they need specialists who will constantly follow the latest findings, and apply them to transformer research, development, design and manufacture. Electric-power industry owns and manages a large number of various types of transformers, and therefore it needs specialists who will follow new trends in transformer production and management. Apart from that, the fact that in Europe there is no postgraduate specialist study in transformers reinforces additionally the reasons for starting a study of this kind, and opens good prospects for its internationalisation. Therefore, the first essential for introduction of this study in the education of specialists for transformer production and usage is the necessity to improve research, development, design, production and usage of transformers through inclusion of latest findings from different transformer-related areas. Faculty of Electrical Engineering and Computing has rich experience in postgraduate education. Postgraduate studies for master’s degree were kept on the Faculty of Electrical Engineering and Computing from 1961 to 2005, and in 1998 a three-year doctoral study has been introduced. Postgraduate specialist study ensure a high level of applied, scientific and instructional work in the transformer field through collaboration of the Zagreb University and Končar Group. Our goal is to train specialists for transformers needed in industry, higher education and research.
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