Transformer components the principle parts of a transformer and their functions are. Current transformers can be mounted on the low voltage or high voltage leads of a power transformer. Current transformers current transformers cts provide a simple, inexpensive and yet accurate means of sensing current flow in power conductors. The basics of current transformers nk technologies. Module transformers this module introduces transformer theory and includes the types of transformers, voltagecurrent relationships, and application. Module 14 test instruments and measuring devices this module describes electrical measuring and test equipment and includes the. The nominal secondary current is rated at 1a or 5a for ease of measurement. Abb instrument transformers current transformer theory technical level training course 201203.
A study of the current transformer with particular. High voltage sf6 current transformers image source. Pdf saturation analysis of current transformer researchgate. Such measuring transformers are required to produce a scaled down replica of the input quantity to the accuracy expected for the particular measurement. Generally, aircore transformers are used when the voltage source has a high frequency above 20 khz.
Generally current transformers are designed such a way that, its. Current transformers cts are used throughout the world as current transducers for protective relays in industrial, commercial, and utlity applications. The current density is an important parameter in amperes circuital law one of maxwells equations, which relates current density to magnetic field. A protection core is designed to transform a distortionfree signal even well into. Current transformers reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the. Instrument transformers are special types of transformers intended to measure currents and voltages. Download fulltext pdf calculation of current transformer transient errors article pdf available in ieee transactions on power apparatus and systems 976. Figure 4 works well for most instrument transformers. Commonly used core materials are air, soft iron, and steel. Ring core cts are available for measuring currents from 50 to 5000 amps, with windows power conductor opening size from 1 to 8.
The latest version of the software can be downloaded for pcs running windows xpvista. A current transformer ct is a type of transformer that is used to reduce or multiply an alternating current ac. Real transformers on the other hand are not 100% efficient and at full load, the efficiency of a transformer is between 94% to 96% which is quiet good. It produces a current in its secondary which is proportional to the current in its primary. Instrument transformers include potential, or voltage, transformers and current transformers. The navy electricity and electronics training series module. All books are in clear copy here, and all files are secure so dont worry about it. Instrument transformers scale the large values of voltage or current to small.
Standard ratings and application guides deal with the steadystate sine wave behavior of current transformers. In special relativity theory, charge and current are combined into a 4vector. The specific performance characteristics of instrument transformers are easily determined from the equivalent circuit. Our antivirus analysis shows that this download is malware free. Zb burden impedance ip primary current ns number of secondary turns ratio to 1 v 3.
Load loss is present only when the transformer is loaded, since the magnitude of the noload current is so small as to produce negligible resistive loss in the windings. There are, however, some phenomena that occur in large transformers, and. S note that the order of the numbers when expressing a transformers turns ratio value is very important as the turns ratio 3. Transformer windings are no exception and these give rise to the load loss or copper loss of the transformer. Pdf current transformers ct are the key device in power system protection. Voltage is produced in any conductor in a changing magnetic field current flowing in the coil on one side of the transformer induces a. Transformers the current in the first coil is usually called the primary current and the current in the second wire is the secondary current.
Tests have shown values ranging from 500 to 11,000 volts. Magnetizing currents in power transformers measurements. Electronic transformers top results of your surfing electronic transformers start download portable document format pdf and ebooks electronic books free online rating news 20162017 is books that can provide inspiration, insight, knowledge to the reader. Voltage is produced in any conductor in a changing magnetic field current flowing in the coil on one side of the transformer induces a voltage in the coil on the other side. Applications of current transformers current transformers are used extensively for measuring current and monitoring the operation of the power grid. Current transformers cts provide a simple, inexpensive and yet accurate means of. Basic transformer operation can be described by two formulae relating the transformation ratio to.
Instrument transformers convert signal levels from dangerous high voltage or inconvenient high current, or current at high voltage to levels appropriate for metering. Current transformer white paper the basics of current transformers ratio the ct ratio is the ratio of primary current input to secondary current output at full load. However, a comprehensive theoretical basis together with application of modern computational techniques is necessary to. If the voltmeter is showing voltage that is sum of both primary and secondary voltage, what will be marking at b choose x1 and x2. Chapter 16 current transformer design university of north. Unique to a current transformer the current transformer function is different than that of a voltage transformer. Polarity refers to the instantaneous direction of the primary current with respect to the secondary current and is determined by the way the transformer leads are brought out of the case. The basics of current transformers ratio the ct ratio is the ratio of primary current input to secondary current output at full load. If the voltage or current in a power circuit are too high to connect measuring instruments or relays directly, coupling is made through transformers. The current density vector is defined as a vector whose magnitude is the electric current per crosssectional area at a given point in space, its direction being that of the motion of the positive charges at this point. In high frequency transformers eddy current losses are reduced by using a core made of a ceramic. Current transformer basics and the current transformer.
Some of these books are still relevant and widely referred for understanding the theory and operation of transformers. Pdf calculation of current transformer transient errors. Within electrical systems, current transformers are essential to ensure the correct functioning and control of equipment and for providing operational data and. Many of the standard books on transformers are now more than 10 years old. Apr 25, 2017 the current transformer the current transformer c. Courtesy siemens current transformers cts are used to convert highlevel currents to a smaller more reasonable level for use as inputs to protection relays and metering equipment. Ieee standard requirements for instrument transformers sponsored by the. The navy electricity and electronics training series neets was developed for use by personnel in many electrical and electronicrelated navy ratings. Ring core cts are available for measuring currents from 50 to 5000 amps, with windows power conductor opening size from 1 to 8 diameter. Construction can be one single primary turn as in toroidal, doughnut, or bar types.
Electrical tutorial about current transformer basics and current transformer theory on how the current transformer works with just one secondary winding. In the previous eleven editions the publishers endeavoured to revise the work, extend it and to bring it up to date. Current transformers, along with voltage or potential transformers, are instrument transformers. The ct ratio is the ratio of primary current input to secondary current output at full load. Electric theory, quantities and circuit elements current typical current levels. A current transformer has a primary winding, a core and a secondary winding, although some transformers, including current transformers, use an air core. The basic theory regarding accuracy classes, ratio and phase errors etc is the same.
Since the load current passes through primary windings in the. Womens classicsunit 14 transformers objectives after studying this unit, the student will be able to state the purpose of a transformer. The navy electricity and electronics training series. Written by, and with the advice of, senior technicians in these ratings, this series provides beginners with fundamental electrical and electronic concepts through selfstudy. A current transformer operates with a set primary current and will try to output a constant current to the load, independent of the load. In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. Current transformers for a shortcircuited transformer the following is valid. Permit the use of standard current ratings for secondary equipment. This is called electromagnetic induction because the current in the first coil causes or induces. On subtractive polarity transformers the h1 primary lead and the x1 secondary lead will be on the same. Assuming an ideal transformer and the phase angles. Current transformers cts are used to convert high level currents to a smaller more reasonable level for use as inputs to protection relays and metering equipment.
Current transformers s 3 current transformer function reduce power system current to lower value for measurement. A protection core is designed to transform a distortion free signal even well into the overcurrent range. Within electrical systems, current transformers are essential to ensure the correct functioning. Ieee standard requirements for instrument transformers. For a transformer operating with a constant voltage and frequency with a very high capacity, the efficiency may be as high as 98%. For current transformers, the value of the reactance x is determined in a special way so that it represents the leakage flux. What weve done here is pass an electric current through empty space from one coil of wire to another.
You have reached 0 of 0 points, 0 not categorized 0% question 1 of 15. Instrument transformers are commonly used with ac instruments when high voltages or large currents are to be measured. The essentials of current transformers in power circuits. Current transformers cts provide a simple, inexpensive and yet accurate means of sensing current flow in power conductors. What is the working principle of a current transformer. Ebook electronic transformers as pdf download portable.
While the physical principles are the same, the details of a current transformer compared with a voltage transformer will differ owing to different requirements of the application. Calculation of current densities in matter free currents. Scribd is the worlds largest social reading and publishing site. Current transformers cts basic theory basic formula. The composition of a transformer core depends on voltage, current, and frequency. A current transformers primary coil is always connected in series with the main conductor giving rise to it also being referred to as a series transformer. Pdf abb instrument transformers current transformer. Basics, maintenance, and diagnostics vii contents continued page 4. The most popular versions among the software users are 3. The current installer available for download occupies 288.
Current transformers play an important role in the monitoring and protection of electrical power systems. Relays are required to perform in fault current type situations moderate accuracy over a wider range. There are, however, some phenomena that occur in large transformers, and in transformers with high rated voltages. Both singlephase and threephase transformers can be diagnosed using this method, and the measurements can beeasily performed at any facility capable of measuring the noload loss. Similarly, current transformers take a high current and reduce it to typically 5 amps on the secondary winding so that it can be used with a watthour meter, ammeter. This enables the protective relays to measure the fault current value accurately, even in very high current conditions. Relays are required to perform in fault current type situations moderate accuracy over a. The alternate current transformer in theory and practice. Each of these materials is suitable for certain applications. Basics, maintenance, and diagnostics book pdf free download link book now. Instrument transformers application guide abb group.
Basics, maintenance, and diagnostics book pdf free download link or read online here in pdf. Cts current transformers pts potential transformers. However, a comprehensive theoretical basis together with application of. Electrical transformer quiz questions electrician exams. Cts are instrument transformers used for converting primary current into a reduced secondary current for use with meters, relays, control equipment and other instruments. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext.
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