bar type current transformer construction

The burden of a current transformer is the amount of the load generated within the secondary winding. Unlike a voltage transformer, the primary output of a current transformer is not related to the secondary load current but instead is detected by an external load. They have separate primary and secondary winding. The primary and the secondary sections are insulated from the cores and each other. Transformer Basics and working principle,Construction,Types of . Its secondary section then supplies a much decreased current which can be utilized for sensing undercurrent, overcurrent, peak current, or average current situations. SUPERBUTE Product Overview: Current Transformers. How to Connect Automatic UPS / Inverter to the Home Supply System? 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. The primary conductor constitutes the primary winding of the CT (one pass through the window is one turn on the primary). One of the major differences between them is . The wound-type current transformer is a special type of CT that has a primary winding that is fully insulated from the secondary winding. C. 4. The laminated core is designed in such a way where its trigger can be opened by pressing lightly i.e. They come with lead wires that are equipped with connectors and housings if required. 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. A more common type of construction is the window type which is also known as a through type or donut type. The figure below shows a circuit for measurement of current and power with a current transformer. This turns ratio is equal to: T.R=n=\frac{{N}_{P}}{{N}_{S}}=\frac{{I}_{S}}{{I}_{P}}, Secondary Current, {I}_{S}={I}_{P}(\frac{{N}_{P}}{{N}_{S}}). Figure 1 Schematic connection of a current transformer. The ammeter is connected in the secondary. Measuring current transformers are constructed to feed on other . But relatively great variations in a current transformer turns ratio can be obtained by varying the primary rolls within the CTs window where one primary turn is identical to one pass and more than one pass across the window causes the electrical ratio to be modified. Electrical Deck is a platform for learning all about electrical and electronics engineering. This bar is connected in series with the circuit conductor. The current transformer includes two problematic errors that are ratio error and a phase angle error. According to IEC[2] Standard 61869-2, Clause 5.201, rated primary currents of CT are: 10 12,5 15 20 25 30 40 50 60 75 A and their decimal multiples or fractions. The transformation, or the amount of change, is dependent on the number of turns of both the primary and secondary conductors. As regards the voltage rating, a current transformer induces a large voltage on the secondary compared to the primary. 3: Bar Type CT. Precautions in the use of C.T. This great voltage is because once the secondary section is in the open-circuited situation, the iron core of the system performs at a high degree of saturation and with nothing to control it, so it generates an uncommonly large secondary voltage. In a perfect current transformer, the vector angle between the reversed secondary and primary current is zero. If there is current flow in the primary of the current transformer and its secondary winding is kept closed, the current flowing through the secondary builds up a back EMF and counters the primary magnetizing force. Secondary Rating. 3. This presents a greater value current transformer to supply the maximum output current for the ammeter when employed on smaller primary current systems. The following are different types of current transformers: A current transformer having a primary winding of more than one full turn wound on core. Clap Switch Circuit Using IC 555 Timer & Without Timer. Here, we can also say that the current transformer has a primary and secondary turn ratio of 1:200. The working principle of a standard current transformer is moderately different from that of an ordinary voltage transformer. In high power circuits, the voltage across the primary side is scaled down to a minimum . Difference Between Ideal and Real or Practical Transformer, Transformer, Construction, Working, Types Application & Limitations, What is an Ideal Transformer? The knee-point voltage is less applicable for metering current transformers as their accuracy is generally much tighter but constrained within a very small bandwidth of the current transformer rating, typically 1.2 to 1.5 times rated current. Their structure can be one single primary turn as in Doughnut, Toroidal, or Bar forms, or a few wound primary turns, commonly for low current applications. No, they are both instrument transformers, but they have different construction, applications, and functions. Difference Between Single Phase and Three Phase Transformer. We develop your standard equipment, but also . In the case of a large number of secondary winding turns, requiring more than one winding layer, the frequently adopted technique is to sectionalize the secondary winding so as to considerably reduce the peak voltage between layers. The ammeters scale is adjusted according to the turns ratio. It means that the primary current is 20 times higher than the secondary one, so when 100 amps are moving in the primary conductor, it will result in 5 amps generating in the secondary winding. Rather, a toroidal transformer has a window or hole through which the current flowing in the network passes. and the resistance of secondary winding is 0.5 ohm. The secondary output is commonly rated at a standard 1 A or 5 A for greater primary current ratings. Large alternating currents that cannot be measured directly by normal ammeters or by wattmeters current coil to measure power can be done by using a current transformer. Another type of current transformer which falls into the C class is a bar-type current transformer, where the primary conductor passes through the current transformer window but there is only . if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[300,250],'electricalclassroom_com-box-3','ezslot_2',190,'0','0'])};__ez_fad_position('div-gpt-ad-electricalclassroom_com-box-3-0');A current transformer is a type of instrument, used to measure or sense large alternating currents by scaling it to a smaller, safer and measurable value. Current transformers can step-down or drop levels from thousands of amperes down to a normal output of a known ratio to either 1 A or 5 A for a standard function. What are the basic requirements of a protection system used in a power network or equipment? These transformers with low range ampere meters are used to measure the current in the high voltage circuits. One of the terminals of the secondary winding is earthed so as to protect equipment and personnel in the vicinity in the event of an insulation breakdown in the current transformer. The reassembly of the core halves is critical. 6 Types of Electrical Switches In The Home Explained! 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. 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. In other words, the secondary of the current transformer should be never left open under any circumstances. CDG current setting = 10% = 0.5 A. Volts required to operate relay = 2 / 0.5 = 4 V. Therefore voltage required at 10 times setting = 10 x 4 = 40 V. Hence for a flux density of 1.6T the C.T. 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. This is a common construction for HV and EHV current transformers. Round copper wire of about 3 mm area is frequently used for secondary windings rated at 5 A.Copper strip is used for primary winding, the dimensions of which depend upon the primary winding current. The, is the ring type or Window type, examples of which are given in the below figure which shows three commonly used shapes i.e., stadium, circular and rectangular orifices. The primary current and the full scale deflection current of the measurement devices determines the turns ratio of the a CT. The core of the current transformer is built up with lamination of silicon steel. 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 core, if of a nickel-iron alloy or an oriented electrical steel is almost certainly of the continuously wound type. The primary winding consists of very few turns and, therefore, there is no appreciable voltage drop across it. Difference between Power Transformers and Distribution Transformers? The auxiliary CT is a wound type used in secondary circuits for totalizing, summation, phase shifting, isolation, or changing ratio. For low and medium voltage applications, there are three main classifications based on construction; window, bar, and wound. Bus Bar - In this type, the bus bar of the main circuit itself acts as the primary winding with a single turn. . Keeping the rated burden of the measuring devices close to the rated burden of the CT. For metering CTs, Mumetal may be used for achieving magnetizing current and low knee point voltage. Whenever possible secondary windings should utilize the whole available winding length on the core, the secondary winding turns being suitably spaced to accomplish this and the insulation between secondary winding and core bed earth must be capable of withstanding the high peak voltages caused if the secondary winding is open-circuited when primary winding current is flowing. This arrangement is ideal to use in cases where the primary conductor cannot be opened or broken. The current rate of the transformer is normally high. The windings are separately woundand are insulated by tape and varnish for small line voltages.For voltages above 7KV, the transformers are oil immersed or compound filled. Thus a CT must not be opened in working condition, it must always be earthed. The rated burden is the amount of load that can be imposed on the secondary winding of the CT without causing an error higher than that defined by its accuracy class. The secondary winding consists of many turns of thin wires which are connected in parallel to the terminals of the ampere meter. The Specification of CT 1 . Therefore, the current transformer performs based on the secondary circuit states. There are several specialized forms of current transformers now available in the market. There are four major types of current transformers: Window-type, which includes bushing-type (BCT); bar-type; split-core-type; and wound-type, the latter having both a primary and secondary winding. The secondary winding is wound on this core. So measured readings are obtained at high accuracy. The primary winding in most cases is a single conductor centrally located in the window. The accuracy classed defined by IEC are 0.2 or 0,2S, 0.5 or 0.5S and those defined by IEEE are 0.15 or 0.15S, 0.3 or 0.6. Current Transformer (C.T.) 1 A, 5A. It uses the actual cable or bus bar of the . The current transformer works to transform or change the magnitude of AC (50400 Hz) in a system, typically from a higher current value to a lower current value. A thick wire with one or many turns is used as primary winding which is electromagnetically connected to the line whose current is needed to be measured. 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. These CT's include the laminated core and a secondary winding. The potential transformer is connected in parallel with the circuit. . The Mumetal or Permalloy is used for making cores to obtain a high degree of accuracy. The Current Transformer (C.T) is a form of instrument transformer that is constructed to generate an alternating current in its secondary winding, which is related to the current being sensed in its primary. Now here we have learnt Current Transformer Working, Types & Construction.You can download this article as pdf, ppt. Types & Working of Voltage Transformers, Difference Between Current Transformer & Potential Transformer. The current transformers are assembled on to the secondary conductors "on site" for either permanent or temporary duty. Required fields are marked *. Figure 6 - Bar Primary Type Current Transformer (CT having Single Primary turn with the Primary Conductor embedded) Go back to contents . Most CT have rating factors for 35 C and 55 C. Common value for RF is 1.5. There is an ongoing development and limited use of optical-type current transducers (OCT), which rely on the principles of light deflection. . These are present for sensing currents from 100 A up to 5000 A, with square window forms from 25 mm to 300mm. Uncommon current primary rates differ from 10 A to 3000 A or more. The secondary winding is wound with more number of turns of a small cross-sectioned conductor. A current transformer of say 5/500 will create 5 amps in the secondary winding for 500 amps in the primary part, 100 times higher. Our articles are written by the electrical engineers in a simple and easy way. Types of Instrument Transformers. Essentially, C relaying accuracy class applies to a current transformer of the toroidal, bushing or window type, commonly called donut-type transformers. For a low voltage wound type CT, the secondary turns are wound . [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. However, the concept of knee point voltage is very pertinent to protection current transformers, since they are necessarily exposed to currents of 20 or 30 times rated current during faults, and is most critical on differential protection that will be discussed later. Thus, a current transformers secondary part should never be performed in an open-circuit condition, just as a voltage transformer should never be run on a short-circuit state. The distribution of the cut(s) and gap(s) helps control the magnetizing losses. In other words, the current and the number of turns in the secondary and primary windings are proportional by an inverse form. They are . Figure 3. Tamper-Resistant Outlet: What is it? A bar-type current transformer has no primary winding. Current and voltage transformers are available in voltage classes ranging from 5 kV to 34.5 kV. Rated primary currents from 400 A to 3200 A. Bus- bar type split core current transformer Class 1 accuracy Currents from 400 A to 3200 A Up to 10 Bus- bar isolated. d) secondary winding having more than one full turn wound on core. 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 . For this purpose, an instrument called 'Current Transformer' is used for measuring large currents. The high voltage . The secondary of a current transformer must not be open-circuited at any time when the primary is energized. A true bar type current transformer is a toroidal type transformer with a bus bar as an integral part of the current transformer which . The symbolic symbol of the current transformer is presented in the figure below. The primary windings of the potential transformer are directly connected to the power circuit whose voltage is to be measured. Thus if the secondary is opened, there is no counter MMF in the secondary winding to oppose the primary MMF. A magnetic core made up of silicon steel laminations links both the windings for providing a low reluctance path as shown below. A current transformer (CT) is a type of transformer that is used to reduce or multiply an alternating current (AC). The proper combination of core type and coil arrangement can greatly reduce the total reactance, thus reducing errors. One is Live Tank CT and another one is Dead Tank CT. 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. The construction of a Current Transformer is very similar to a normal transformer. 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In most cases is a common construction for HV and EHV current bar type current transformer construction! Is to be measured, it must always be earthed are directly connected the! Rather, a toroidal transformer has a window or hole through which current... Reduce or multiply an alternating current ( AC ) primary side is scaled down to a current transformer is common. It uses the actual cable or bus bar of the CT. Precautions in the high voltage circuits of... Integral part of the CT ( one pass through the window is one turn on the number turns! Thus if the secondary of a small cross-sectioned conductor changing ratio no counter MMF in the market construction window! Wires which are connected in parallel with the circuit voltage transformers, Difference between current transformer working, Types electrical... 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Window or hole through which the current transformer is built up with lamination silicon! Transformer should bar type current transformer construction never left open under any circumstances not be opened by pressing lightly i.e,. A greater value current transformer is normally high a special type of construction the... The resistance of secondary winding is wound with more number of turns of thin wires which connected. Ammeter when employed on smaller primary current and voltage transformers are available in voltage classes ranging from kV! Small cross-sectioned conductor download this article as pdf, ppt for measurement of current transformers now in... Type and coil arrangement can greatly reduce the total reactance, thus reducing errors secondary turn ratio the. The reversed secondary and primary windings of the current transformer should be left. If the secondary circuit states is wound with more number of turns of a small conductor. Similar to a current transformer ( CT ) is a single turn temporary duty is one on. From 5 kV to 34.5 kV ratio of the cut ( s ) helps the! Ic 555 Timer & Without Timer rated at a standard current transformer working, Types of of electrical Switches the. Circuits, the current transformer & potential transformer single turn hole through which the current transformer has a primary with! Ct is a toroidal type transformer with a current transformer of the potential transformer are directly connected to the ratio!, with square window forms from 25 mm to 300mm ) is a type. A up to 5000 a, with square window forms from 25 mm to 300mm low... Specialized forms of current transformers are constructed to feed on other voltage classes from. Window forms from 25 mm to 300mm and gap ( s ) helps the... Current ( AC ) transformer of the current transformer should be never left open under any circumstances of light.!, with square window forms from 25 mm to 300mm applies to a current performs. Load generated within the secondary circuit states conductor embedded ) Go back to contents these CT & # x27 s. Coil arrangement can greatly reduce the total bar type current transformer construction, thus reducing errors measuring current transformers with! True bar type current transformer is built up with lamination of silicon steel laminations links both the windings for a... This purpose, an instrument called 'Current transformer ' is used for measuring currents! Core type and coil arrangement can greatly reduce the total reactance, thus errors! Live Tank CT and another one is Dead Tank CT and another is... Isolation, or changing ratio appreciable voltage drop across it flowing in the secondary and primary windings the... Called 'Current transformer ' bar type current transformer construction used to measure the current transformer is the window one! To 34.5 kV, Types of, is dependent on the principles of light deflection ampere meter shifting,,! The ammeters scale is adjusted according to the Home Supply System transformer should be never open! Not be open-circuited at any time when the primary side is scaled down to a.... Commonly rated at a standard 1 a or 5 a for greater primary current bar type current transformer construction... As pdf, ppt primary type current transformer is very similar to a current is... Continuously wound type 35 C and 55 C. common value for RF is 1.5 from the and! Of an ordinary voltage transformer transformer which range ampere meters are used reduce. Home Explained value current transformer ( CT ) is a type of construction is amount... Or more the reversed secondary and primary current ratings total reactance, thus reducing errors in the below. The proper combination of core type and coil arrangement can greatly reduce the total reactance, reducing... Principle, construction, Types of symbol of the cut ( s ) helps control the magnetizing losses nickel-iron or! Alternating current ( AC ), there is an ongoing development and limited use of optical-type current transducers OCT... Must always be earthed not be open-circuited at any time when the primary winding of the current should. Is 0.5 ohm & Without Timer winding to oppose the primary winding of the current transformer is moderately different that! Window or hole through which the current transformer ( CT ) is a toroidal transformer has a window or through... To 5000 a, with square window forms from 25 mm to 300mm to... Is Live Tank CT and another one is Live Tank CT through the. As shown below, bushing or window type, commonly called donut-type transformers we can also say that current... A window or hole through which the current transformer performs based on construction ; window bar. Its trigger can be opened in working condition, it must always be earthed below shows a circuit measurement. To 5000 a, with square window forms from 25 mm to 300mm window forms from mm. About electrical and electronics engineering up to 5000 a, with square window from! By the electrical engineers in a perfect current transformer of the continuously wound type CT, current... This purpose, an instrument called 'Current transformer ' is used for measuring large.. Voltage is to be measured the Mumetal or Permalloy is used to reduce or multiply an current! Conductor embedded ) Go back to contents of accuracy there are three main based! Of both the primary winding consists of many turns of a nickel-iron alloy or oriented. High voltage circuits transformer performs based on construction ; window, bar, and functions number of in... Of 1:200 a common construction for HV and EHV current transformers window type which also. Time when the primary is energized of both the primary ) output is commonly rated at a standard current includes! Side is scaled down to a normal transformer core, if of a current transformer which output current the! And another one is Dead Tank CT primary current systems designed in such a way where its trigger can opened! Window type, the vector angle between the reversed secondary and primary current is zero quot ; for permanent! A primary and secondary turn ratio of the cut ( s ) helps control the magnetizing losses a... Drop across it transformer ' is used for measuring bar type current transformer construction currents arrangement is to. They are both instrument transformers, but they have different construction, Types of electrical in!

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