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Current transformers live typically wont to measure currents of high magnitude. These transformers step down the present to be measured so it may be measured with a traditional vary meter. A Current electrical device has only 1 or only a few numbers of primary turns. the first winding could also be simply a conductor or a bus bar placed in an exceedingly hollow core (as shown within the figure). The secondary features a sizable amount turns accurately wound for a particular turns quantitative relation. so the present electrical device steps up (increases) the voltage whereas stepping down (lowering) the present.

Generally, current electrical devices and meters area unit used along as a matched combine during which the look of this transformer is like to produce a most secondary current appreciate a complete deflection on the ammeter. In most current transformers Associate in Nursing approximate inverse turns magnitude relation exists between the 2 currents within the primary and secondary windings. this can be why the standardization of the CT is mostly for a selected variety of meter.

Most current transformers have the quality secondary rating of five amps with the first and secondary currents being expressed as a magnitude relation like 100/5. this implies that the first current is twenty times bigger than the second current thus once a hundred amps area unit flowing within the primary conductor it’ll lead to five amps flowing within the secondary. A current electrical device of say 500/5, can manufacture five amps within the secondary for five hundred amps within the primary conductor, a hundred times bigger.

By increasing the number of secondary windings, Ns, the secondary current is created a lot of smaller than this within the primary circuit being measured as a result of as Ns will increase, Is goes down by a proportional quantity. In alternative words, the number of turns and therefore the current within the primary Associate in Nursing secondary windings area unit connected by an inverse proportion.

### CT  Types

Measuring current transformers. These current transformers are used beside the measurement devices for the mensuration of current, energy, and power.
Protective current transformers. These current transformers are used beside protecting instrumentality like trip coils, relays, etc.
Based on the perform construction, it can even be classified as follows:

Bar Type: this sort consists of a bar of appropriate size and therefore the material forming associate integral a part of the electrical device.

Wound Type: this sort incorporates a primary coil of quite one full flip wound over the core.

Window kind: this sort has no primary coil. The secondary of the CT is placed around the current flowing conductor. The magnetic field of force created by current flowing through the conductor induces this within the secondary, that is employed for mensuration.