Current transformer measurement or protection system can convert a high voltage into a low voltage and a large current into a small current. Basically, it is used to convert high voltage or high current into standard low voltage (100V) or standard low current (5A or 1A, all in proportion to the rated value) in order to standardize and reduce the size of measuring instruments, protection equipment, and automatic control devices. Additionally, the transformer can be used to isolate high-voltage systems to ensure the safety of personnel and equipment.
Current Transformer Working Principle
In the power supply line, the current difference can range from a few amperes to tens of thousands of amperes, and the voltage difference can range from a few volts to several million volts. Due to the high current and voltage in the line, direct measurement is extremely dangerous. Transformers play the roles of transformer transformation and electrical isolation in order to facilitate the measurement of the secondary instrument. Since most of the display instruments are pointer-type current and voltage meters, the secondary currents of the current transformers are measured in amperes (e.g., 5). Most electricity measurement has become digital, and the signal sampled by the computer is usually at the milliamp level (0-5V, 4-20mA, etc.). The miniature current transformer’s secondary current is milliampere, which mainly serves as a bridge between the transformer and the sampling circuit. Instrument current transformers are miniature current transformers.
Similarly to the transformer, the miniature current transformer also works on the principle of electromagnetic induction. The transformer transforms voltage while the miniature current transformer transforms current. The primary winding N1 is connected to the measured current, and it is also known as the primary winding. There is a secondary winding (or secondary winding or secondary winding) that connects N2 to the measuring instrument.
It is the ratio of the primary winding current I1 to the secondary winding current I2 of the miniature current transformer that is known as the actual current ratio K. Known as Kn, the rated current ratio of the miniature current transformer is the current ratio when it works under its rated working current. Kn=I1n/I2n
