Basic electrical theory overview of ac motors, transformers and measuring instruments. The navy electricity and electronics training series. Ring core cts are available for measuring currents from 50 to 5000 amps, with windows power conductor opening size from 1 to 8 diameter. Kirchoffs current and voltage laws kcl and kvl kirchoffs current law. Unique to a current transformer the current transformer function is different than that of a voltage transformer. Written by, and with the advice of, senior technicians in these ratings, this series provides beginners with fundamental electrical and electronic concepts through selfstudy. Schneider electrics extensive power monitoring product portfolio. Like the power transformer, the current transformer also contains a primary and a secondary winding. Apr 25, 2017 the current transformer the current transformer c. Kcl states that the total current entering a junction is equal to the total current leaving the junction. This portable document format pdf file contains bookmarks, thumbnails, and hyperlinks to help you navigate through the document. Instrument transformer basic technical information and. Schneider electric is the global specialist in energy management with the most complete power. Schiff the laplace transform is a wonderful tool for solving ordinary and partial differential equations and has enjoyed much success in this realm.
Current transformers cts provide a simple, inexpensive and yet accurate means of sensing current flow in power conductors. Its secondary winding then provides a much reduced current which can be used for detecting overcurrent, undercurrent, peak current, or average current conditions. Ring core cts are available for measuring currents from 50 to 5000 amps, with windows power conductor opening size from 1 to 8. Commonly used core materials are air, soft iron, and steel. What weve done here is pass an electric current through empty space from one coil of wire to another. The navy electricity and electronics training series module. Cts current transformers pts potential transformers. With its success, however, a certain casualness has been bred concerning its application, without much regard for hypotheses. Oct 08, 2016 applications of current transformers current transformers are used extensively for measuring current and monitoring the operation of the power grid. Current transformers current transformers cts provide a simple, inexpensive and yet accurate means of sensing current flow in power conductors. Transformers the current in the first coil is usually called the primary current and the current in the second wire is the secondary current. For current transformers, the value of the reactance x is determined in a special way so that it represents the leakage flux. The ct ratio is the ratio of primary current input to secondary current output at full.
Additional protection current transformers at tata steel. 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. It can be designed to step up or step down voltages and works on the magnetic induction principle. Tests have shown values ranging from 500 to 11,000 volts. 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, or protection relay. Within electrical systems, current transformers are essential to ensure the correct functioning and control of equipment and for providing operational data and. Module transformers this module introduces transformer theory and includes the types of transformers, voltagecurrent relationships, and application. Current transformers for a shortcircuited transformer the following is valid. In high frequency transformers eddy current losses are reduced by using a core made of a ceramic. Jun 24, 2018 electrical transformer theory and concepts 1 how transformer works. Phase voltage, line voltage, and current in a wye system the relationship between the line voltage, and line current, and the winding, or phase voltage and phase current, in a threephase wye circuit can be seen in figure 128. Current transformer principle of operation of ct some.
The composition of a transformer core depends on voltage, current, and frequency. Within electrical systems, current transformers are essential to ensure the correct functioning. Current transformer basics and current transformer theory. Note the fused cutout and lighting arrestor combination external to the transformer. This module introduces transformer theory and includes the types of transformers, voltagecurrent relationships, and application. Depending on the application, these transformers can be classified as distribution transformers and power transformers. Current transformers cts basic theory basic formula. Assuming an ideal transformer and the phase angles. One winding consists of fewer turns of heavier wire on the steel core.
A current transformer is an instrument transformer, used along with measuring or protective devices, in which the secondary current is proportional to the primary current under normal conditions of operation and differs from it by an angle that is approximately zero. In this case there are no movement to get the relative motion between the. Voltage and current relationship of a threephase delta circuit. Figure 4 works well for most instrument transformers. The basics of current transformers ratio the ct ratio is the ratio of primary current input to secondary current output at full load. Module transformers this module introduces transformer theory and includes the types of transformers, voltage current relationships, and application. Nov 15, 2019 the basic principle of the current transformer is the same as that of the power transformer. This is called electromagnetic induction because the current in the first coil causes or induces. Transformer windings are no exception and these give rise to the load loss or copper loss of the transformer. With its success, however, a certain casualness has been bred concerning its application, without much regard for hypotheses and when they are valid. Complete basics and theory of electrical transformer.
What is the working principle of a current transformer. 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. Current transformers are essential components designed to be used with. A transformer has no moving parts and is a completely. Current transformers reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the actual electrical current flowing in. 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. 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. In this case there are no movement to get the relative motion between the constant flux and the conductor. Transformers are used to increase or decrease the alternating volta ges in electric power applications. According to the design, transformers can be classified into two. This module introduces transformer theory and includes the types of transformers, voltagecurrent relationships, and.
Then to summarise, the current transformer, ct is a type of instrument transformer used to convert a primary current into a secondary current through a magnetic medium. 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. High voltage sf6 current transformers image source. Voltage regulation in transformers is the difference between the no load voltage and the full load voltage. The navy electricity and electronics training series neets was developed for use by personnel in many electrical and electronicrelated navy ratings. S note that the order of the numbers when expressing a transformers turns ratio value is very important as the turns ratio 3. Introduction to alternating current and transformers. Equivalent current transformer circuit x 1 primary leakage reactance r 1 primary winding resistance x 2 secondary leakage reactance z 0 magnetizing impedance r. Figure 30 simplified schematic of current circuit for m2001d paralleling two transformers using the circulating current method 52 figure 31 paralleling scheme. The types of transformers differ in the manner in which the primary and secondary coils are provided around the laminated steel core. Zb burden impedance ip primary current ns number of secondary turns ratio to 1 v 3. Whenever an alternating current flows through the primary winding, alternating magnetic flux is produced, which then induces alternating current in the. In coretype transformer, the windings are given to a considerable part of the core.
Current transformers perform the following functions. Instrument transformers are special types of transformers intended to measure currents and voltages. 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. A current transformer operates with a set primary current and will try to output a constant current to the load, independent of the load. Generally, aircore transformers are used when the voltage source has a high frequency above 20 khz. Each of these materials is suitable for certain applications. The specific performance characteristics of instrument transformers are easily determined from the equivalent circuit. Transformer as a static device uses the electromagnetic induction principle of faradays law of electromagnetic induction. Potential transformers consist of two separate windings on a common magnetic steel core.
Abstractpower transformers can fail from dielectric stresses caused by. A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. Transformer basicsworking principle,construction,types. Electrical transformer theory and concepts 1 how transformer works. Applications of current transformers current transformers are used extensively for measuring current and monitoring the operation of the power grid. Current transformers can be mounted on the low voltage or high voltage leads of a power transformer.
The basics of current transformers nk technologies. In the previous eleven editions the publishers endeavoured to revise the work, extend it and to bring it up to date. Current transformers are usually either measuring or protective types. Module 14 test instruments and measuring devices this module describes electrical measuring and test equipment and includes the. On subtractive polarity transformers the h1 primary lead and the x1 secondary lead will be on the same.
Since the invention of th e first constantpotential transformer in 1885, transformers have. A transformer delivers 100 volts at no load and the voltage drops to 95 volts at full load, the regulation would be 5%. The two major types of construction of transforme rs used in transmission and distribution of electrical energy are core type and shell type. Current transformers reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the. 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. Kod ktf remanence only considered in extra high voltage systems ehv k tfvalues acc. Current transformer basics and the current transformer. A distinction has to be made between a metering class and a protection class current transformer.