áramváltó

Áramváltó, often translated as current transformer, is a type of instrument transformer used to measure or control high alternating currents. It is designed to produce a current in its secondary winding that is proportional to the current flowing in its primary winding. This allows high currents, which would be too dangerous or difficult to measure directly with standard instruments, to be safely and accurately measured using lower-rated equipment.

The basic principle of operation relies on electromagnetic induction. A primary winding, which may consist of just a single turn or the main power conductor passing through a toroidal core, carries the high current. A secondary winding is wound around the same magnetic core, and this winding has many more turns than the primary. According to Faraday's law of induction, the voltage induced in the secondary coil is proportional to the rate of change of magnetic flux, which in turn is proportional to the primary current. This induced voltage drives a current in the secondary circuit.

Current transformers are characterized by their transformation ratio, which is the ratio of the primary current to the secondary current. This ratio is typically standardized, such as 100/5 A or 200/1 A, meaning that for every 100 or 200 amperes flowing in the primary, 1 ampere flows in the secondary. The secondary circuit is always connected to a low-impedance load, such as an ammeter or a relay coil, to maintain the proportionality and accuracy. It is crucial that the secondary of a current transformer is never left open-circuited while the primary is energized, as this can lead to dangerously high voltages and damage to the transformer.