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Current Transformers

Current transformers for measurement are sensors that allow taking measurements of high currents and converting them to lower currents, which can be read by measuring equipment. They are often used when a current is too high to be measured directly. Thus, they are used to safely monitor the current. At SACI we have a wide variety of transformers, discover them!

Our catalog of transformers

At SACI you will find a wide variety of transformers such as TA_P mini split open core, TU_PS narrow profile or TU_ resin, among others. Considering their construction, you can find, wound primary or bus-bar current transformers. Wound primary transformers are usually less expensive than bus-bar transformers, but are less accurate. On the other hand, bus-bar transformers are usually found in installations where the voltage is 25kV or less and give more accurate results by reducing flux leakage.

Advantages of current transformers

These instruments have many advantages such as:

    • They allow large currents to be measured safely, as they reduce the high voltage current to lower, safer levels.
    • They provide electrical isolation between the high voltage circuit and the measuring devices, protecting personnel from possible electric shock.
    • They act as control devices to actuate protective devices, such as relays and pilot lights.
    • They have a very accurate measurement of electric currents without the need to interrupt the main circuit.

Current transformer VS. voltage transformer

These are safe instruments for measuring high value currents and voltages very accurately. However, there are a number of differences between them. For example, the current transformer transforms a high input current into a low output current and the voltage transformer transforms the high input voltage into a low output voltage. Moreover, the former is connected in series with the instrument and the latter is connected in parallel. As for the number of primary and secondary turns, the current one has a small number of primary turns compared to that of the secondary winding. On the other hand, the voltage one has a very large number of turns in the primary compared to the secondary. There are many other differences, but the most important are the first two differences mentioned above.

Solutions for all types of industrial applications

The flexibility of current transformers allows them to be used in many different situations and in all types of industries. For example, they can be used to measure current in commercial revenue metering applications, protect against power lines and power substations, measure current with hand tools…

FAQS about transformers

Industrial currents are usually too high to pass directly to measuring devices. That is why current transformers are used, to reduce to acceptable values in the vast majority of instruments, usually less than 5 amperes. Thus, a current transformer (CT) is used to obtain a lower but proportional current to that passing through a power line.

It is used to measure the high current flowing through a line, as well as an isolation device between power circuits and digital measuring instruments.

It’s operation is quite similar to that of a conventional two-voltage transformer. As mentioned above, a current transformer is used to measure high currents. When high current flows through the primary core of the transformer, it induces a minimum current through the secondary taking into account the number of turns of both voltages. A low range ammeter connected through the secondary is capable of measuring the current through the secondary. Thus, if the number of turns in the primary and secondary is known, in addition to the value of the secondary current measured with the ammeter, it can be used to determine the high value current flowing through the primary.

To answer this question, several factors must be considered. First of all, it is important to take into account the current range that the transformer can withstand. It is also interesting to consider the accuracy, since depending on the use (measurement, protection or control) the level of accuracy required may vary. However, there are many other criteria depending on the needs of each individual. If you need advice, do not hesitate to contact us!

A transformer consists of a sheet metal core that facilitates magnetic flux and two windings: the primary, which receives the input current, and the secondary, which delivers the output current. The windings are electrically insulated to prevent short circuits. In addition, the transformer has a protective casing, usually with dielectric oil for cooling and additional insulation, as well as connection terminals and protective devices such as relays.

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