For current transformers, the value of the reactance x is determined in a special way so that it represents the leakage flux. Using a reactance to represent the magnetizing leg of a ct, as shown in figure 1, is a useful visual concept. If a term has more than one abbreviation left column, below, our preferred abbreviation is listed first. Transformer an electrical device, without continuously moving parts, which, by electromagnetic induction, transforms energy from one or more circuits to other circuits at the same frequency, usually with changed values of voltage and current. Determine that the primary range of the current transformer encompasses the application requirement. The list below shows how we abbreviate in our books. In a typical utility application, transformers are connected. 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. Scribd is the worlds largest social reading and publishing site. Transformer rated services run in parallel with the service. High voltage products pa 123pa 145 current transformer.
Current transformer a current transformer ct is a type of transformer that is used to reduce or multiply an alternating current ac. It produces a current in its secondary which is proportional to the current in its primary. Current transformer circuits for power electronics applications. Ring core cts are available for measuring currents from 50 to 5000 amps, with windows power conductor opening size from 1 to 8 diameter. Constant current transformer how is constant current. The classification of protection current transformers follows the following. Emergency power off button or switch electric water cooler. The current transformer will operate into either a short circuit or a resistive load until the voltage induced is enough to. 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. Abb instrument transformers buyers guide edition 5, 200803 b2 explanations technical specifications current transformers currents the rated currents are the values of primary and secondary currents on which performance is based. Current transformers current transformers cts provide a simple, inexpensive and yet accurate means of sensing current flow in power conductors. There are two issues with core design that affect differential relaying.
Abbreviations commonly used in electrical documents. The current transformer function is different than that of a voltage transformer. Work from home or in the office access cad drawings anywhere with electra cloud electra cloud learn more sign me up work from home or in the office learn more sign me up electra cloud is the next generation, cloud based electrical schematic software that lets you access your drawings from anywhere, with just a browser electra cloud. Schneider electric instrument transformers steven engineering. Current transformer basics and the current transformer. Some people refer to the meters that use a ct pt combination or just cts as a current transformer meter. Mutual induction is the process by which a coil of wire magnetically. Using leadingedge wireless sensor networking technology ecowizard offers various energy measurement modes such as watthour by rs485, current transformer, and pulse inputs, while significantly reducing the installation costs associated with current solutions. Current transformers reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the. Capacitor, condenser, compensator, carrier current, case, or compressor. 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.
The ip5 a ratio current transformer delivers at the secondary a current is of 0 to 5 a that is proportional to the current measured at the primary ip. Eddy current and current induced by the external magnetic field figure 2. The amount of electricity, in kva or voltamperes, supplied by the transformer. Chapter 16 current transformer design university of north. Current transformers, along with voltage or potential transformers, are instrument transformers. Circulating current in thick, medium and thin laminations figure 2. Pa 123pa 145 current transformer installation and operation manual your safety first. Current transformer cos power factor referring to sinusoidal procedures cos. Types of transformer different types of transformer.
Showbiz for each circuit breaker, one current transformer of 3 coils has to be included, the size of which depends upon the rating of the circuit breaker. Current transformer how is current transformer abbreviated. In other applications, a reactor is used, and in some applications, the ground fault current is limited to less than 10a. Figure 405 error diagram of a current transformer class 0,2 at 5 % of rated current. List of abbreviations ct current transformer ed eskom distribution cigre conference internationale des grandes reseaux electriques hv high voltage iec international. While the latter configuration would not be used today, one may be required to make this calculation on an existing system. The ct ratio is the ratio of primary current input to secondary current output at full load. Instrument transformers scale the large values of voltage or current to small. Transformer short circuit current calculation and solutions. Nov 15, 2019 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 which is approximately zero. The specific performance characteristics of instrument transformers are easily determined from the equivalent circuit. Current transformers are essential components designed to be used with schneider electrics extensive power monitoring product portfolio.
This type of transformer is categorized on the basis of a number of turns in the primary and secondary windings and the induced emf. 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. Lower or specialized ratios may be obtained by adding primary and secondary turns as shown on page 52. Agme american gear manufacturers association ah amperehour capacity of batteries. This allows them to be used in combination with measurement equipment. The transformer is used to transfer electrical energy from high voltage windingto low voltage winding or vice versa through magnetic field. A current transformer ct is a type of transformer that is used to reduce or multiply an alternating current ac.
When an ac voltage is applied to one coil, current flowing in that coil magnetizes the core first in one direction, then in the opposite direction. For consultation, design and interpretation of components, devices and electrical circuit diagrams and electronic keywords. This is the reason why our instruction begins with the following guidelines. The electric power industry uses a lot of abbreviations, and not always in the same formats. Basics, maintenance, and diagnostics vii contents continued page 4.
Apr 16, 2011 current transformers principle of operation of ct. A transformer with the core and coils immersed in liquid as opposed to a drytype transformer. A current transformer can be modeled as a constant current source where ratio current is injected into a magnetizing impedance in parallel with the burdens shown in figure 1. Power factor referring to fundamental frequency cos. Megan fox, star of the current transformers film, also has a horror film coming out called jennifers body. The construction of transformers varies greatly, depending on their applications, winding voltage and current ratings and operating frequencies.
A variety of specialized symbols originally used for aircraft applications have been added to make. If the abbreviation has more than one meaning the right column, t. The current transformer can be designed with either primary or secondary reconnection or a com bination of both. A current transformer operates with a set primary current and will try to output a constant current to the load, independent of the load. Equivalent current transformer circuit x 1 primary leakage reactance r 1 primary winding resistance x 2 secondary leakage reactance z 0 magnetizing impedance r 2 secondary winding resistance z b secondary load note. The basics of current transformers nk technologies. Loads are expressed as a function of the current flowing in the transformer, and not according to the watts consumed by the equipment the transformer feeds. Typical electrical drawing symbols and conventions. The various types of transformer shown in the figure above are explained in detail below. The current transformer is designed to connect in series with the line to transform the line current to the standard 5 amperes suitable for the. Figure 4 works well for most instrument transformers.
Its secondary winding then provides a much reduced current which can be used for detecting overcurrent, undercurrent, peak current, or average current conditions. And pdf full form of all elecrical circuit breakers. This means that unlike selfcontained services the customers. When cts and pts are used in a metering installation, the installation is known as being transformer rated. 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. Find out what is the most common shorthand of transformer on abbreviations. Singlephase transformers connected into a 3phase bank retain all basic singlephase properties individual voltage and current transformations are based on the singlephase turns ratio phase shift between primary and secondary is zero 3phase transformer banks can introduce a. The paper will show the balanced transformer output current in terms of the flux in the core that is due to load current, which invites discussion on how load flux distributes in a core. Select the proper window size or slightly larger to fit your primary conductor. Observe the technical data given in the rating plate and in the specification. If a ct test switch is used, the switch must have a makebeforebreak contact pattern to.
Abbreviations commonly used in electrical documents a a amperes, amps. Current transformers technical datasheet schneider electric is the global specialist in energy management with the most complete power monitoring product line. The page contains a list of abbreviations and its full forms, which are commonly used in electrical and electronics engineering. A current transformer, abbreviated ct, is a type of transformer used to measure the current of a given circuit.
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