Observe the technical data given in the rating plate and in the specification. I am je of nagbhir sub station of 225 kv newly electrified section and testing started of current transformer when test ct ratio by injecting current in primary bushing of old ct which was 20 years old ct installed in circuit,after testing values not found according to ratio,100 amps inject and found in secondary terminal 3. Learn how transformers work, how to create a magnetic field with electricity, why only an alternating current can be used in transformers, how a basic transformer works, step up and step down transformers and finally three phase transformers. Current transformer definition use of ct working principle. Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not. The working principle of the current transformer is slightly different from the power transformer. The ratio between the primary current and the secondary current, i1i2, is called the current ratio of current transformer. Centre tapped transformer working principle of a centre tapped transformer a centre tapped transformer works in more or less the same way as a usual transformer. The other, a protective current transformer, is used along with. Transformers are an electrical component that transmit electrical energy between at least two circuits. Determine the flow direction of the energy in the cable that you wish to measure. Current transformers, along with voltage or potential transformers, are instrument transformers. The current transformer is designed to connect in series with the line to transform the line current to the. Current and voltage relation in step down transformer.
This principle is explained in further detail below. Instrument transformers scale the large values of voltage or current to small. Current transformer ct construction and working principle. 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. Core balance current transformer or cbct is a ring type current transformer through center of which a three core cable or three single core cables of three phase system passes. In some, the bar carrying high current may act as a primary. What is the working principle of a current transformer. The first, a measuring current transformer, is used along with measuring devices for the magnitude of current, energy and power.
P1 indicates the side on which the current source is located, whilst p2 indicates the load side. The transformer is used to transfer electrical energy from high voltage windingto low voltage winding or vice versa through magnetic field. 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. The working principle of a transformer is very simple. A basic transformer consists of two coils that are electrically separate and inductive, but are magnetically linked through a path of reluctance. For example, many cell phones, laptops, video games, and power tools and small appliances have a transformer built into their plugin unit like that in figure 1 that changes 120 v or 240 v ac into whatever. It produces an alternating current ac in its secondary which is proportional to the ac current in its primary. However, it differs in the way in which the primary and the secondary are interrelated. As it is a step down transformer we have less voltage at secondary which is nearly 15 to 45 volts and has high current values which is nearly 200 a to 600 a it can also be higher than this value. The whole point of a current transformer is that it transforms current, not voltage. Instrument transformer basic technical information and. A current transformer ct basically has a primary coil of one or more turns of heavy crosssectional area. Working principle of autotransformer your electrical guide. Pdf instrument current transformers cts measure ac currents.
Electrical transformer is a static electrical machine which transforms electrical power from one circuit to another circuit, without changing the frequency. This is the first part of video series called as current transformer in this video i have discussed about definition of current transformer and working principle of it. Instrument transformers potential transformer, current transformers for high voltage and current measurement. It produces a current in its secondary which is proportional to the current in its primary. This type of current transformer is normally used for earth fault protection for low and medium voltage system. In a twowinding transformer, primary and secondary are only magnetically linked by a common core but are completely insulated from each other but in the case of an auto transformer. Working principle, construction and types of transformer. Transformers are used to transfer electric power from one end to another through the medium of magnetic field. Current transformers, along with voltage or potential transformers are instrument transformer. In a current transformer, the loads impedance or burden on the secondary has slightly differed from the power transformers.
A clear understanding of how transformers work is nectssary in order to wire them properly in an electrical system. Cts are basically stepup voltage transformers, on the other hand, these are stepdown transformers in view of current. Transformers do what their name impliesthey transform voltages from one value to another the term voltage is used rather than emf, because transformers have internal resistance. A current transformer ct is a type of transformer that is used to measure ac current. A transformer has no moving parts and is a completely. This is the reason why our instruction begins with the following guidelines. The basic working of ct is similar to that of pt, but the primary winding of the current transformer is connected in series with high power lines. A current transformer is a device that is used for the transformation of current from a higher value into a proportionate current to a lower value. Transformer basicsworking principle,construction,types. A distinction has to be made between a metering class and a protection class current transformer. Welding transformer working principle and applications. Current transformer circuits for power electronics. High voltage products pa 123pa 145 current transformer.
This is even applicable to a step down transformer. In this video you will learn about what is current transformer, important concepts of current transformer, how current transformer work, use of. A transformer is a static electrical device that transfers electrical ene rgy between two or more circuits through electromagnetic induction. Thus, the current transformer operates on secondary circuit conditions. Pdf dccompensated current transformer researchgate. Basics, maintenance, and diagnostics vii contents continued page 4. Current transformer basics and the current transformer. Electrical tutorial about current transformer basics and current transformer theory on how the current transformer works with just one secondary winding. Current transformers are usedin measuring high currents and connected with it in parallel to it. One is a continuous operation level and one is for emergency conditions. The difference lies in just the fact that its secondary winding is divided into two parts, so two individual voltages can be acquired across the two line ends. Working flux leakage flux which flows in the core represented by reactance x core auxiliary winding on outer leg of core connected in parallel a b c zi figure 4. In this video you will learn about what is current transformer, important concepts of current transformer, how current transformer work, use of current transformer. Ring core cts are available for measuring currents from 50 to 5000 amps, with windows power conductor opening size from 1 to 8.
Current transformers can be classified into two separate groups. Transformer working principle the main principle of operation of a transformer is mutual inductance between two circuits which is linked by a common magnetic flux. Working principle of a transformer the basic principle on which the transformer works is faradays law of electromagnetic induction or mutual induction between the two coils. Understanding input and output current and grounding are particularly troublesome. A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. Transformer only stepup or stepdown the level of ac voltage or ac current. The construction of transformers varies greatly, depending on their applications, winding voltage and current ratings and operating frequencies. It transforms the high voltage current into the low voltage current due to which the heavy current flows through the transmission lines is safely monitored by the ammeter. It is either used to provide isolation between two circuits or to step up or step down the voltage and current. Transformer can increase or decrease the voltage with corresponding decrease or increase in current.
Core balance current transformer electrical concepts. The basic principle of the current transformer is the same as that of the power transformer. Current transformer danger when secondary is left open. Current transformers cts provide a simple, inexpensive and yet accurate means of sensing current flow in power conductors. This is connected in series with the line carrying high current. The operation of current transformer is similar to the conventional power transformer. One important thing to note is that this trick works only if the electric current is fluctuating in some way. The ratio of the primary to the secondary, the ratio of the input to the output, and the turns ratio of any given transformer will be the same as its voltage ratio.
A current transformer ct is a type of transformer that is used to reduce or multiply an alternating current ac. A current transformer ct is a type of transformer that is used to reduce or multiply an. 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 an ac. The working principle of autotransformer and construction is similar to that of conventional two winding transformers. Mutual induction between two or more windings also known as coils allows for electrical energy to be transferred between circuits. Current transformer design guide an effective design of a ring type c. The actual number of turns of wire on any winding is generally not important. Transformers do not work with direct current dc, where a steady current constantly flows in the same direction.
The current transformer is used with its primary winding connected in series with line carrying the current to be measured and, therefore, the primary current is dependant upon the load connected to the system and is not determined by the load burden connected on the secondary winding of the current transformer. In other words, you have to use a type of constantly reversing electricity called alternating current ac with a transformer. Electrical transformer basic construction, working and. Installation of current transformers janitza electronics. The transformer consists of two separate windings placed over the. A dualvoltage transformer can be ruined when power is applied, if the connections are made improperly. It can be designed to step up or step down voltages and works on the magnetic induction principle. It is based on current transformer description its working and applications are present in it,it also includes videos of its windings and its inrush ability of transformer, and also about instrument transformer and its working with applications. But, since the voltage at the secondary of a step down transformer is lesser than that at the primary, the current at the secondary will be increased in order to balance the total power in the transformer.
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