[Current Transformer] What is a current transformer? What are the functions and types of current transformers?
What is a circuit transformer?
A current transformer converts a large primary current into a secondary current based on the principle of electromagnetic induction. An instrument for measuring small currents on the secondary side. The current transformer is composed of a closed core and windings. Its primary winding has a small number of turns and is strung in the circuit of the current that needs to be measured.
Therefore, it often has all the current of the line flowing through it. The secondary side winding has a relatively large number of turns and is connected in series to the measuring instrument and protection circuit. When the current transformer is working, its secondary side circuit It is always closed, so the impedance of the measuring instrument and the series coil of the protection circuit is very small, and the working state of the current transformer is close to short circuit. The current transformer converts the large current on the primary side into the small current on the secondary side for measurement. The secondary side cannot be opened.
The function of current transformer
The function of current transformer is to convert a larger primary current 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 transformation ratio of 400/5 can convert an actual current of 400A into a current of 5A.
Current transformer model
Model meaning: first letter: L—current transformer; second letter: A—wall-through type; Z— Pillar type; M—Busbar type; D—Single-turn through type; V—Inverted structure type; Third letter: Z—Epoxy resin casting type; C—Porcelain insulation; Q—Gas insulation medium; W—Special for microcomputer protection .
Current transformer ratio
General current transformer ratio is: ?/5? is the number you want to choose, 5 is fixed. It means changing the actual current into 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, it cannot be less than your actual measured current (that is, if you want to install a transformer there, you need to know what the current is there). It must not be less than your test current, but it cannot be too much greater than the actual current, half. Controlled at 1.5% of the actual currentThat’s it.
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