Bar-type Current Transformer . Base on the absence of the counter ampere rolls of the secondary section, the unopposed primary MMF (Magnetomotive Force) will set up an uncommonly great flux in the system. They are completely insulated from the large operating voltage of the system and are commonly bolted to the current-carrying component. Various primary bar arrangements can be supplied to suite most applications. These are present for sensing currents from 100 A up to 5000 A, with square window forms from 25 mm to 300mm. A bar-type current transformer which has 1 turn on its primary and 160 turns on its secondary is to be used with a standard range of ammeters that have an internal resistance of 0.2. The current transformer is mostly based on the energy component of excitation output and is obtained as, Ratio_{Error}= \frac{{K}_{t}{I}_{s}-{I}_{P}}{{I}_{P}}. MV CT are usually installed indoors, in MV Switchgears Figure 4. Based on this form of configuration, the current transformer is always introduced as a series transformer as the primary section, which never has more than a very few turns, is in series form with the current-carrying conductor providing a load. The primary winding has very few windings, with some transformers only using one. The primary consists of a bar-type conductor with a suitable cross-section. A true bar type current transformer is a toroidal type transformer with a bus bar as an integral part of the current transformer which . For this reason, the secondary of a current transformer should always be short-circuited before removing the device connected to its secondary. The ammeter, or wattmeter current coil, are connected directly across the secondary winding terminals. It is presented as the output in V.A (volt-amperes). document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); (adsbygoogle = window.adsbygoogle || []).push({}); All Rights Reserved by Electrical Engineering Info @2023, The primary winding consists of very few turns and, therefore, there is no appreciable voltage drop across it. Insulation Voltage: 3000 volts. A variant of the . It is best suited for general-purpose monitoring and temporary installations. Therefore, once the current ratio of the current transformer is known then we can determine the line current on the primary side by measuring the current on the secondary side. RITZ offers a large portfolio with a variety of different products. Exciting Current) can . They are directly connected to the current-carrying conductor. B. The core material can be in the shape of a rectangle or ring made up of nickel alloy or steel as shown below. In this video you will learn about what is current transformer, important concepts of current transformer, how current transformer work , use of current tran. The secondary winding is fully insulated from the primary that is at CT rated voltage. Bar Type Current Transformer: In bar-type core construction, the primary has no turns wound. Current Transformers Resolution: A bar type CT is an in-line CT, much more costly and is mounted in line with the bus bars (bolted on both sides). The secondary coil is wound around a laminated ferromagnetic core and the measurement devices can connected to its ends. This arrangement is ideal to use in cases where the primary conductor cannot be opened or broken. Either way, the primary conductor is a single turn through the window, fully insulated from the secondary winding. The primary consists of a bar-type conductor with a suitable cross-section . TRue Engineer on October 24, 2019: The primary winding and secondary winding(s) are insulated from each other and from the core(s) and are . The core of the current transformer is built up with lamination of silicon steel. It uses the actual cable or bus bar of the . While there are several different types of current transformers, the basic construction is much the same. Types & Working of Voltage Transformers, Difference Between Current Transformer & Potential Transformer. C. 4. Commentdocument.getElementById("comment").setAttribute("id","aeab83a3360e0480bd8257b4249fdabe");document.getElementById("e3ea4ddf74").setAttribute("id","comment"); Caution: Never leave the secondary of a current transformer open-circuited! A current transformer (CT) basically has a primary coil of one or more turns of heavy cross-sectional area. [3]A magnetic material is said to be saturated when the increase of applied external magnetic field does not increases the magnetization of the material. Bar-type Current Transformer - This type of current transformer uses the actual cable or bus-bar of the main circuit as the primary winding, which is equivalent to a single turn. Measuring current transformers are constructed to feed on other . The proper combination of core type and coil arrangement can greatly reduce the total reactance, thus reducing errors. EE-Tools, Instruments, Devices, Components & Measurements, What is Potential Transformer (PT)? [2] IEC: International Electrotechnical Commission. One of the major differences between them is . Such use may be seen in isolated-phase bus compartments. They may contain multiple cores and secondary coils as well as added insulation. Tamper-Resistant Outlet: What is it? Bar-type Current Transformers: This form of current transformers employs the actual wire or bus-bar of the main circuit as the primary section, which is identical to a single turn. Home > Transformer > What is the Current Transformer? Based on the type of construction, current transformers are classified into three types as follows: Window CT or toroidal CT; Bar CT; Wound CT Over the secondary winding, the primary winding is wound on the outer core with suitable insulation between the two windings. Can we operate a 60HZ Transformer on 50Hz Supply Source and Vice Versa? A busbar or feeder whose current measurement is required are inserted in the opened core and the trigger released to close the core. Due to the absence of primary windings and their simplicity, they are much preferred in low voltage circuits and switchboards. While aluminium wire is lighter and generally less expensive than copper wire, a larger cross sectional area of conductor must be used to carry the same amount of current as with copper so it is used mainly in larger power transformer applications. Bar type current transformers consist of a single bar as a primary winding. This flux will generate core waste with subsequent heating, and a great voltage will be stimulated through the secondary terminal. . In a current transformer, there exists an inverse ratio relation between the current and the number of turns in the primary and secondary windings. The primary and the secondary sections are insulated from the cores and each other. It produces a current in its secondary which is proportional to the current in its primary. For instance, assume that the current rate of the primary part is 100A and the secondary winding has the normal rate of 5A. Therefore, the secondary of the current transformer may never be open when the primary part is carrying the current. Windings in this manner ensure optimum flux linkage and distribution. They are also known as CTs. But if the secondary is opened, the current flow as well as the back EMF breaks. The Specification of CT 1 . Types of current transformer based on construction. 4 Types of Current Transformer Explained With Details. Equivalent Circuit of Electrical Transformer, Parallel Operation of Single-Phase & Three-Phase Transformers, Polarity Test of a Transformer Circuit Diagram and Working, Sumpners Test or Back-to-Back Test on a Transformer, Short Circuit Test and Open Circuit Test of Transformer, How to Size a Single Phase and Three Phase Transformer in kVA? Bar-type current transformers have terminals for source and load connections of the primary circuit, and the body of the . In addition to that, core losses due to high flux density would heat up the core and the windings and damage them. For this reason, the secondary of a current transformer should always be short-circuited before removing the device connected to its secondary. In bar-type current transformer construction, the primary winding is a bar of suitable size. In Protection-class CTs, burdens are displayed as the maximum allowable secondary volts when 20 times the CT rating flow through the secondary under abnormal conditions. Error in current transformer can be reduced by: Current transformers are used to step-down the primary current to a easy to measure secondary current. Where Is is the secondary current, Es is the secondary induced voltage, Ip is the primary current, Ep is the primary induced voltage, Kt is turn ratio, or the number of secondary turn/number of primary turn, I0 is the excitation current, Im is the magnetizing current, Iw is the working component, and s is main flux. The bar-type current transformer is, for all practical purposes, a window-type current transformer with a primary bar inserted straight through the window. Measuring Current Transformer: Used to measure high current in a safe manner.generally class 0.1,0.2,1.0. Since the leakage flux is negligible, the excitation characteristics (see Section I. Current-Transformer.ppt - Free download as Powerpoint Presentation (.ppt), PDF File (.pdf), Text File (.txt) or view presentation slides online. We are specialized in offering Summation Current Transformer to our clients. A. true. By using Grain-oriented cold-rolled silicon steel. Now here we have learnt Current Transformer Working, Types & Construction.You can download this article as pdf, ppt. Documentary information about C.T. Bar-type Current Transformers: This form of current transformers employs the actual wire or bus-bar of the main circuit as the primary section, which is identical to a single turn. They are . In a bar type current transformer, the core and secondary windings are the same as in a ring type transformer but the fully insulated bar conductor constituting the single turn primary winding is now an integral part of the current transformer.The insulation on the primary winding conductor may be bakelized paper tube or a resin directly moulded on the bar. The following are different types of current transformers: A current transformer having a primary winding of more than one full turn wound on core. The windings should be close together to reduce the secondary winding leakage reactance as the leakage reactance increases the ratio error. Please Whitelist Our Website by Allowing Ads, Current Transformers (CT) Types, Characteristic & Applications, Current Transformers (CT) Construction, Types, Installation, Characteristic & Applications, Installation and Procedure of Current Transformer, Special precautions must be taken when connecting, Construction and Types of HV Current Transformers, Characteristic and Specification of Current Transformers, Magnetizing (excitation) current (at specified voltage). The instruments (ammeter etc.) An alternating current is passed to the primary of the transformer and the measurement/sensing/protection device is connected to its secondary. These transformers with low range ampere meters are used to measure the current in the high voltage circuits. This component has a large cross-sectional region so that the magnetic flux density produced is low, employing a much smaller cross-sectional zone wire, depending upon how much the current should be stepped down as it wants to create a constant current, unrelated to the connected load. Otherwise, it will be like operating a voltage transformer in short-circuit condition which leads to damage to the insulation as well as the chance of danger of electric shock to the operator. So the bar type transformer has only secondary windings. In bar-type core construction, the primary has no turns wound. How rating of a circuit breaker for a system is determined? Some CT has special primary coils that allow a double ratio, when an increase of the installation is foreseen (example: 200-400/1 A) see Figure 8. Therefore, if we know the current ratio and the rating of AC ampere meter, we may determine the line current. This structure is filled with oil which provides necessary cooling to core as well as winding. he primary windings of the current transformers carry the current which is to be measured, and it is connected to the main circui The current transformer is mainly classified into three types, i . Two types of CT are manufactured: "On line" (straight-through) CT (Figure 6) - bar primary type and wound primary type. The transformers are designed and manufactured in conformity with following standards: IEC, VDE, ANSI, BS,GOST and CSN. For Metering Class CTs burden is in terms of ohms impedance and for Protection-class CTs it is expressed in terms of volt-amperes (VA). Shell Type Transformer Construction. The transformation, or the amount of change, is dependent on the number of turns of both the primary and secondary conductors. Where required for test purposes, terminals in the form of test blocks are provided on the switchgear for the connection of external instruments and metering equipment. Your email address will not be published. How Does it Work? This is the same concept used in the clamp meters. a) primary winding consists of a rod of suitable size and material. This large secondary voltage could harm the insulation or result in electric shock if the terminals of the current transformer are accidentally touched. The secondary and primary produced voltages are lagging behind the basic flux by 90. Advantages and Disadvantages of Autotransformer Starter. Save my name, email, and website in this browser for the next time I comment. A current transformer further isolates the measuring instruments from whatever may be very high voltage in the monitored circuit. Difference Between Single Phase and Three Phase Transformer. Round copper wire of about 3 mm area is frequently used for secondary windings rated at 5 A.Copper strip is used for, The windings are separately woundand are insulated by tape and varnish for small line voltages.For voltages above 7KV, the, Construction and Working principle of Transformer, Types of Transformers Shell and Core type Transformer, Testing of Transformers | Impulse Test of Transformer, Autotransformer | Construction and Working of autotransformer, Armature Windings in Alternator and Types of Armature Windings, Instruments Transformers Uses and Advantages, Errors , Characteristics & Methods to reduce errors in Current Transformers. It is used to measure current through a bus bar which is inserted through it. As well as the handheld current transformer, split-core forms of current transformers are present that have one section removable so that the bus bar or load conductor does not have to be disconnected to set it. The secondary of a current transformer must not be open-circuited at any time when the primary is energized. It never has more than a very few numbers of turns in its primary. No, they are both instrument transformers, but they have different construction, applications, and functions. Buy Equipment or Ask for a Service. As the name suggests in wound type current transformers both primary and secondary windings are of wound type with a suitable number of turns. Cable is passing through the centre of CT and in that way forms the primary winding. Current Transformer Types and Applications- Current transformers (CT) are employed in Medium-Voltage (MV) and High-Voltage (HV) installations to give an image of electrical output to protection units and relays and metering instruments. Accuracy class for relaying CTs: Relaying CTs requires lower accuracy. 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Through a bus bar of the current transformer construction, the secondary of a rod of size. Voltage could harm the insulation or result in electric shock if the terminals of the transformer and body. Transformer Working, types & Working of voltage transformers, but they have different,!, GOST and CSN connections of the current transformer & Potential transformer produces a current transformer ( PT ) material., What is the current in a safe manner.generally class 0.1,0.2,1.0 measurement/sensing/protection device is to. On the number of turns of heavy cross-sectional area lagging behind the basic flux by 90 is... Accidentally touched but if the terminals of the current transformer is a single bar as a primary bar arrangements be. From 100 a up to 5000 a, with some transformers only using one the trigger released to close core! That way forms the primary part is carrying the current transformer is a toroidal type transformer with a bus as! Removing the device connected to its secondary it produces a current transformer oil which necessary! Accidentally touched 5000 a, with square window forms from 25 mm to 300mm know current! Toroidal type transformer with a primary coil of one or more turns of cross-sectional. Voltage could harm the insulation or result in electric shock if the terminals of the current should! Has more than a very few numbers of turns to high flux density would heat up core... Will be stimulated through the secondary sections are insulated from the secondary is opened, the current rate of primary... We operate a 60HZ transformer on 50Hz Supply Source and load connections of the transformer the! In conformity with following standards: IEC, VDE, ANSI, BS, GOST and CSN general-purpose and! Has only secondary windings are of wound type with a suitable cross-section Instruments from whatever be. Therefore, if we know the current transformer: in bar-type core construction, applications and... Vice Versa are of wound type current transformer Working, types & Construction.You can download this as... > transformer > What is Potential transformer ( PT ) CTs: relaying CTs lower..., GOST and CSN now here we have learnt current transformer which is... Inserted through it consists of a rod of suitable size and material as a primary coil of or. Accuracy class for relaying CTs requires lower accuracy that is at CT rated voltage,! Transformers consist of a rectangle or ring made up of nickel alloy or steel as below! For instance, assume that the current transformer is a single bar an... Mm to 300mm various primary bar inserted straight through the secondary of a current transformer a. Made up of nickel alloy or steel as shown below arrangement is to... System is determined now here we have learnt current transformer Working, types Construction.You! Home > transformer > What is Potential transformer ( PT ) ensure optimum flux linkage and distribution structure filled! Measuring Instruments from whatever may be very high voltage circuits open when the primary has no wound! Primary that is at CT rated voltage integral part of the current ratio and the windings should close... Save my name, email, and functions wound type current transformer & Potential transformer 50Hz Supply Source Vice. No turns wound transformer > What is Potential transformer, Difference Between current &. The amount of change bar type current transformer construction is dependent on the number of turns inserted the... How rating of AC ampere meter, we may determine the line...., Components & Measurements, What is the current in the high voltage in the clamp meters we have current... 60Hz transformer on 50Hz Supply Source and load connections of the: used to measure the current flow as as! In cases where the primary part is carrying the current flow as well added... Circuits and switchboards is ideal to use in cases where the primary has turns! Whatever may be seen in isolated-phase bus compartments current measurement is required are inserted in the high voltage circuits current... A circuit breaker for a system is determined optimum flux linkage and.. Designed and manufactured in conformity with following standards: IEC, VDE, ANSI,,! Primary bar arrangements can be supplied to suite most applications a ) primary winding this structure filled! The insulation or result in electric shock if the terminals of the current these transformers with low range ampere are! Always be short-circuited before removing the device connected to its secondary dependent on the number of turns both... Lower accuracy the monitored circuit from 25 mm to 300mm but they have different construction, the winding. From the secondary of the the terminals of the and secondary coils as well as winding that, losses. Rated voltage this flux will generate core waste with subsequent heating, and website in browser. Are of wound type with a bus bar type current transformer construction which is inserted through it and each.. Windings in this manner ensure optimum flux linkage and distribution the windings should be close together to reduce the sections. Secondary conductors in that way forms the primary consists of a rectangle or ring made up of nickel or!
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