In the line of power supply and electricity, the current and voltage vary widely from small to tens of thousands of amps. In order to facilitate the measurement of the secondary instrument, it is necessary to convert to a relatively uniform current, and the voltage on the line is relatively high as direct measurement is very dangerous. The current transformer acts as a transformer and electrical isolation. Most of the display instruments are pointer type current and voltage meters, so the secondary current of the current transformer is mostly amperometric (such as 5). With the development of the times, most of the electricity measurement has been digitized, and the signal sampled by the computer is generally milliampere (0-5V, 4-20mA, etc.). The secondary current of the miniature current transformer is milliampere, which acts as a bridge between the large transformer and the sampling. The miniature current transformer is called the “instrument current transformer”. ("Instrument current transformers" have a meaning of multi-current ratio precision current transformers used in the laboratory, generally used to expand the meter range.)
Current transformer principle circuit diagram Micro current transformer is similar to transformer. It also works according to the principle of electromagnetic induction. The transformer transforms the voltage and the micro current transformer changes the current. The winding N1 is connected to the measured current, which is called the primary winding (or primary winding, primary winding); the winding N2 is connected to the measuring instrument, called secondary winding (or secondary winding, secondary winding).
The ratio of the current of the primary winding current I1 of the micro current transformer to the secondary winding I2 is called the actual current ratio K. The ratio of the current when the miniature current transformer operates at the rated operating current is called the current transformer rated current ratio, expressed as Kn. Kn=I1n/I2n