Current transformers are components used in power supply units, industrial installations and energy sector. They allow to measure high current flowing in wires of controlled installation. For this purpose, meters with small measurement range and sensitive electronic circuitries are used. This is a basic task of current transformers. Another important function of current transformers is to provide galvanic separation between the primary circuit, in which current being measured flows, and secondary winding, to which the meter is connected. Thereby, they ensure high level of safety. Galvanic separation allows to get rid of problems connected with stray voltage, interferences and different ground potentials of both circuits. Therefore, current transformers are used in switched-mode electronic systems in order to measure current flowing through components of power stage.
Operating principle of current transformers resembles operation of transformers. They are shaped as a ring on which secondary winding, to which control circuit is connected, is wound. A wire in which current is measured, is placed inside the ring. It forms one coil of primary winding. Depending on the number of coils in primary winding, the current transformer is equipped has an appropriate ratio, which determines the factor of reduction of the current flowing in the primary circuit.
Apart from a ratio, main parameters of current transformers are:
- temperature range,
- the diameter of the measuring hole (it determines maximum diameter of test leads),
- insulation test voltage (it determines dielectric strength),
- accuracy class (it indicates the accuracy of produced elements and impact of a current transformer structure on accuracy of measurement).
A current transformer on the secondary side has to be loaded with a resistor of a resistance of several dozen ohms; a voltmeter is used to measure voltage on this resistor. The optimal value of this resistance (taking into account the accuracy of measurement and minimal amount of disruption) is provided in the data sheet by the manufacturer. In the data sheet there is also information about maximum value of primary current that can be measured with the use of a given element.
For industrial automation systems, specialised versions are available which produce output signal of 0 ... 20mA or 4 ... 20mA, as well as 0 ... 10V. They are equipped with a built-in electronic preconditioning system and they require an auxiliary power supply unit.
Current transformers available at TME
TME is one of the biggest distributors of electronic components in Europe. Current transformers are delivered to more than 115 countries in the world within the shortest possible time. We constantly expand the territorial reach of our store. Large part of current transformers is available in stock at the time of ordering. In case of product unavailability, we arrange special orders on request and ensure fast delivery to the client.
Descriptions and technical parameters of every product available in our offer can be found on details page. Our customers can also compare the parameters of current transformers offered by us by using our product comparison engine. Thanks to this engine it is possible to compare products offered by various manufacturers.
TME offers a wide choice of other relays, such as solid state relays and installation relays.