The CT current transformer is developed from the principle of electromagnetic induction and consists of a closed iron core and windings. When the equipment is running close to a short circuit, a large current can be converted into a small current according to the set value, and then sent to the secondary instrument, and the relay protection provides energy for the measurement.
What is the difference between the structure of the through-core current transformer and the ordinary current transformer? Next, we will briefly tell you about it, let's find out together!
The structure of the feed-through current transformer itself does not have a primary winding, and the current-carrying (load current) wires from L1 to L2 pass through a circular (or other shape) iron core made of silicon steel sheets to play the role of a primary winding.
The secondary winding is directly and evenly wound on the circular iron core, and forms a closed loop in series with the secondary load of the current coil such as instruments, relays, and transmitters. The number of turns of the winding passing through the core of the transformer is determined. The more the number of through-core turns, the smaller the transformation ratio; on the contrary, the less the number of through-core turns, the larger the transformation ratio, and the rated current ratio I1/n: where I1--A rated current for one turn through the heart; n--the number of turns through the heart.
The structure of the CT current transformer is relatively simple, consisting of a primary winding, a secondary winding, an iron core, a frame, a shell, and a terminal that are insulated from each other.
Its working principle is basically the same as that of the transformer. The number of turns (N1) of the primary winding is less, and it is directly connected in series to the power supply line. When the primary load current (I1) passes through the primary winding, the generated alternating magnetic flux induction produces proportionally reduced Secondary current (I2); the number of turns (N2) of the secondary winding is large, which forms a closed loop in series with the secondary load (Z) of the current coil such as instruments, relays, and transmitters. Equal ampere turns, I1N1=I2N2, the rated current of the current transformer is smaller than the load impedance of the current transformer in actual operation, and the secondary winding is close to a short-circuit state, which is equivalent to a transformer in short-circuit operation.
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