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