[Current Transformer] What is the current transformer? The role and model of the current transformer

[Current Transformer] What is the current transformer, the role and model of the current transformer

What is a circuit transformer

A current transformer is an instrument that converts a large current on the primary side into a small current on the secondary side based on the principle of electromagnetic induction to measure. A current transformer consists of a closed iron core and windings. Its primary side winding has few turns and is connected in the line of the current to be measured.

Therefore, it often has all the current of the line flowing through it, and the secondary winding has a large number of turns. It is connected in series in the measuring instrument and the protection circuit. When the current transformer is working, its secondary circuit It is always closed, so the impedance of the series coil of the measuring instrument and the protection circuit is very small, and the working state of the current transformer is close to a short circuit. The current transformer is to convert the large current on the primary side into a small current on the secondary side for measurement, and the secondary side cannot be opened.

The function of the current transformer

The function of the current transformer is to convert the primary current with a larger value into a smaller value through a certain transformation ratio. The secondary current is used for protection, measurement and other purposes. For example, a current transformer with a ratio of 400/5 can convert an actual current of 400A into a current of 5A.

Current transformer model

Model meaning: the first letter: L—current transformer; the second letter: A—through the wall; Z— Pillar type; M—busbar type; D—single turn through type; V—structure upside down; third letter: Z—epoxy resin casting type; C—porcelain insulation; Q—gas insulating medium; W—special for computer protection .

Current transformer ratio

Generally, the current transformer ratio is: ?/5? is the number you want to choose, 5 is fixed, It means to change the actual current to a current of 5A. For example, if your actual current is 100A, then you can choose a 150/5 transformer. If your actual current is 150A, then you can choose a 200/5 transformer. In short? Can’t be less than your actual measured current (that is, if you want to install a transformer there, you must know what the current is there),? It must not be less than your test current, but it can’t be much larger than the actual current, half Control it to 1.5 of the actual current to accompany it.