A transformer consists of two highly inductive coils windings wound on a steel or iron core. A current transformer can also be used as an input to a current relay or transmitter, or to reduce the current so that a current switch or transducer can be utilized. Potential transformer pt definition the potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to the lower value. For example, a farmer has a large, 480v, 3phase motor powering a well. This technology is commerically available, and offers amazing accuracy. Transformer works on the principle of mutual induction of two coils. The transformer transforms the energy from one circuit to another through electromagnetic induction. Its secondary winding then provides a much reduced current which can be used for detecting overcurrent, undercurrent, peak current, or average current conditions. The next level of detail is the representation of the points where the components merge, shown in figure 9. Feb 12, 2017 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. Simply short the secondary of the ct through the sensing window of the sensor. So, assume you are feeding 16 watts in 4v and 4 amps. When current in the primary coil is changed the flux linked to the secondary coil also changes.
What is transformer,principle of working electrical engineering. Current transformer consists of either one or few primary winding turns due to which it has also been called as series transformer. The working principle of transformer depends upon ohms law. Generator transformer an overview sciencedirect topics. A transformer has no moving parts and is a completely static solid state device, which. Nov 15, 2019 the basic principle of the current transformer is the same as that of the power transformer. 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.
It can be designed to step up or step down voltages and works on the magnetic induction principle. The ideal transformer model neglects the following basic linear aspects of real. What is the basic principle of a 3 phase transformer. The terminal of the transformer should be designed so that the variation of the voltage ratio with load is minimum and the phase shift between the input and output voltage is also minimum. The basic principle of the current transformer is the same as that of the power transformer.
Instrument transformer theory and testing steve hudson, pe. The principle of operation of this type ocr is simple, the ct may use the current in the. The operation of current transformer is similar to the conventional power transformer. F in the other coil which is inductively coupled to the first coil. A transformer is used to lower the voltage from 480 v to 120 v for the lighting circuit. In its basic form, a transformer consists of two coils with high mutual inductance that are. Nov 17, 2019 a transformer is a static device which transfers electrical energy from one circuit to another through the process of electromagnetic induction. It is most commonly used to increase step up or decrease step down voltage levels between circuits. The voltage transformer can be thought of as an electrical component rather than an electronic component.
A current transformer ct is a type of transformer that is used to measure ac current. 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. Instrument transformers application guide abb group. There are countless transistors in the electronic products we use such as mobile phones and computers.
The working principle of the transformer can be understood from the figure below. Sep 16, 2017 a step up transformer is a device which converts the low primary voltage to a high secondary voltage i. The formula of the transformer depends on the voltage and number of turns in the primary and secondary circuit. Transformers can be segmented on the basis of type as distribution transformer, power transformer and others, which includes instrument transformer. 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. When current in the primary coil is changed the flux linked to. The second method is to parallel ct inputs at the transducer.
Section d ry tp ei sbu ona f m 1 transformer questions. 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. Mutual induction between two or more windings also known as coils allows for electrical energy to be transferred between circuits. Chapter 16 current transformer design university of north. What is transformer,principle of working electrical. Pressure coil resistance and current coil resistance. Threephase transformer needs to have 3 coils or windings connected in the proper array to match the incoming power supply. For each depletion layer, the barrier potential is about 0. They are the big brain of the computer the basic components. Current transformers reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the.
Megger working principle types history uses of megger. Jun 02, 2015 working principle of current transformers. The following images shows a simple demonstration of the use of transformers. A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. The motor is in a building, and the farmer wants one 120v circuit for a few lights and a receptacle outlet. Mit5202 5 kv diagnostic insulation resistance tester. A transformer is a passive electrical device that transfers electrical energy from one electrical circuit to another, or multiple circuits. The dc current transformer dcct is a type of dccapable current transformer, which produces an output current proportional to the input current all the way down to dc. Coupled with an ammeter, cts are used to protect the main lines of the power grid, by measuring highvoltage electrical current and preventing damage to sensitive equipment. Current transmission systems facts can alter the total line. As shown above the transformer has primary and secondary windings. Aug 28, 2014 an ideal potential transformer should give secondary voltage exactly in phase with the primary voltage and exactly in phase opposition.
The potential transformer is made with highquality core operating at low flux density so that the magnetising current is small. A dry type transformer is a type of transformer which never uses any insulating liquid where its winding or core are immerged in liquid. Multiple winding transformer and multicoil transformers. A transformer is a device which is use to convert high alternatic voltage to a low alternatic voltage and vice versa. The primary winding of the transformer is directly connected to the high voltage power circuits between two phases or between a phase and ground depending on the transformer rating and its application. Analysis, size, share, business development and regional overview by 2023 transformers cover a very diverse subject area that encompasses both, small and very large components. But practically due to some primary and secondary voltage drops the exact proportional voltage cannot be obtained at the secondary. A current transformer, abbreviated ct, is a type of transformer used to measure the current of a given circuit. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by. 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.
Application of optical current transformers in digital. Current transformer design guide an effective design of a ring type c. The transformer consists of two separate windings placed over the laminated silicon steel core. A transformer is a device used to change the voltage levels of electricity to facilitate the transfer of electricity from generating stations to. Working of potential transformer the electrical portal. This is because the current transformer ct would need to be located at either end of the. The more current that flows, the stronger is the magnetic field. However, the working principle of step down transformer and all these transformers are the same and that is electromagnetic induction. A basic transformer consists of two coils that are electrically separate and inductive, but are magnetically linked through a path of reluctance. An electrical transformer works on the principle of mutual induction, which states that a uniform change in current in a coil will induce an e. The current transformer will operate into either a short circuit or a resistive load until the.
On subtractive polarity transformers the h1 primary lead and the x1 secondary lead will be on the same. The operating staff in such cases will be able to take measures to switch the load over to other feeders and switch. A current transformer operates with a set primary current and will try to output a constant current to the load, independent of the load. Voltage transformer is necessary for directional, voltage, distance protection. This principle is explained in further detail below. One can find variety of current transformers which is an instrument used for measuring and protecting devices. Whenever an alternating current flows through the primary winding, alternating magnetic flux is produced, which then induces alternating current in the. Solved examples using transformer formula included. Core balance current transformers cbcts are employed for providing earth leakage protection in a power system. Whenever an alternating current flows through the primary winding, alternating magnetic flux is produced, which then induces alternating current in the secondary winding. Voltage for testing produced by hand operated megger by rotation of crank in case of hand operated type, a battery is used for electronic tester. Protect instrument from any damage because of low external electrical resistance under test. In insulated or compensated neutral networks, earth leakage currents are small and are. Here is highlighted few important types of current transformer.
Transformer basicsworking principle,construction,types. Potential transformer voltage transformer is used for protection and measurement. 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. The working principle of a transformer is very simple. Actually they are protective type voltage transformer.
To verify that the ct is working at the site we have to test the entire circuit. A variety of types of electrical transformer are made for different purposes. Transformers works on the principle of mutual induction. It produces an alternating current ac in its secondary which is proportional to the ac current in its primary. A varying current in any one coil of the transformer produces a varying. A step down transformer on the other hand, steps down the input voltage i. A current transformer is defined as as an instrument transformer in which the secondary current is substantially proportional to the primary current under normal conditions of operation and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections. Faradays laws of electromagnetic induction, states that the rate of. This provides a transformer with an inherent current limitation due to the loose coupling. A transformer has no moving parts and is a completely. This means your output voltage is 8 volts and your output current is 2 amps and this, in turn, implies a. A transformer is an telectrical apparatus designed to convert alternating current from one voltage to another.
An important property of electricity is that a magnetic field is produced around a wire in which electrical current is flowing. Operating principle of electrical transformer in its simplest form a transformer consists of two windings, the voltage is applied to one set of windings, called the primary, which builds up a magnetic flux through the coupling medium. The main principle of operation of a transformer is mutual inductance between two circuits which is linked by a common magnetic flux. Consequently an emf is induced in the secondary coil. This leads to the transformation of voltage supplied by the power company to the level of voltage that is required to maintain the proper phasing or polarity. If the constant voltage transformer is subjected to a line voltage frequency change the output voltage will vary, as shown in figure 115. Current transformer basics and the current transformer. Working principle of transistors when no voltage is applied across the transistor, diffusion of free electrons across the junctions produces two depletion layers.
The regulation of a constantvoltage transformer can be designed to be better than a few percent. Unique to a current transformer the current transformer function is different than that of a voltage transformer. Cts are basically stepup voltage transformers, on the other hand, these are stepdown transformers in view of current. The transformers are designed for either singlephase supply or threephase supply.
Transformer definitionoperating principle ece tutorials. Working principle of step down transformer your electrical. The principal of operation of a multiple winding transformer is no different. Chapter 16 current transformer design wordpress for the. Current transformer ct construction and working principle. This means your output voltage is 8 volts and your output current is 2 amps and this, in turn, implies a secondary load resistance of 4 ohms. This transformer step down the voltage to a safe limit value which can be easily measured by the ordinary low voltage instrument like a voltmeter, wattmeter and watthour meters, etc. The secondary of the potential transformer is connected various measuring devices and relays. Rather, the windings and core are kept within a sealed tank that is pressurized with air. Ppt instrument transformer powerpoint presentation. What is the working principle of a current transformer.
Octs, were current and voltages are measured with other principles than traditional. Aug 01, 2017 there are countless transistors in the electronic products we use such as mobile phones and computers. Explain principle, working theory of transformer physics. Working principle of a transformer transformer is a static device and doesnt contain on rotating parts, hence no friction losses, which convert electrical power from one circuit to another without changing its frequency. Transformation action depends upon the rate of change of flux linkage between primary and secondary winding of transformers. The current transformer consists of only one or very few turns as its primary winding. Pdf in the paper a method for the compensation of current transformer is proposed. Say you have one winding also known as a coil which is supplied by an. It is possible to combine the use of abb cvts as voltage transformers with. Generally, it is sufficient to incorporate insulation monitoring only to indicate appearance of earth leakage, and not for disconnection. Dc offset and gain accuracies of 10 ppm or better thats 0. The basics of current transformers nk technologies.