There will be a new round of cooling during Christmas. While going out to play, everyone should also pay attention to keeping warm and take personal protective measures.

 

In high current and high voltage coke oven circuits, the range extension method of low range instruments with sufficient leads cannot be used for measurement. Under these conditions, specially constructed precision ratio transformers are called instrument transformers. These voltage and current ratings can be used independently for communication.

These transformers not only expand the range of low range instruments, but also isolate them from current and high voltage AC circuits. This makes its handling very secure. These are generally divided into current transformers and voltage transformers.

Current Transformer (CT):

A current transformer is an instrument that converts high primary current into low secondary current based on the principle of electromagnetic induction for measurement. A current transformer is composed of a closed iron core and winding. Its primary winding has very few turns and is connected in series in the circuit where the current needs to be measured. Therefore, it often has all the current flowing through the circuit, and the secondary winding has a relatively large number of turns. It is connected in series between the measuring instrument and the protection circuit. When the current transformer is working, its secondary circuit is always closed. Therefore, the impedance of the series coil between the measuring instrument and the protection circuit is very small, and the working state of the current transformer is close to a short circuit. A current transformer is used to measure by converting the high current on the primary side into a low current on the secondary side, and the secondary side must not be open circuited.

 

The principle of current transformer [2] is based on the principle of electromagnetic induction. A current transformer is composed of a closed iron core and winding. Its primary winding has very few turns and is connected in series with the line that needs to measure the current, so it often has all the current flowing through the line. The secondary winding has a relatively large number of turns and is connected in series with the measuring instrument and protection circuit. When the current transformer is working, its secondary circuit is always closed, so the impedance of the measuring instrument and protection circuit series coil is very small, and the working state of the current transformer is close to a short circuit.

 

Voltage Transformer (PT):

Voltage transformers, similar to transformers, are instruments used to convert voltage. But the purpose of transformer voltage conversion is to facilitate the transmission of electrical energy, so the capacity is large, usually calculated in kilovolt ampere or megavolt ampere units; The purpose of voltage transformers in converting voltage is mainly to supply power to measuring instruments and relay protection devices, to measure the voltage, power, and electrical energy of lines, or to protect valuable equipment, motors, and transformers in the event of line faults. Therefore, the capacity of voltage transformers is very small, generally only a few volt amperes, tens of volt amperes, and the maximum does not exceed one thousand volt amperes. The entry introduces its basic structure, working principle, main types, wiring methods, precautions, exceptions and handling, as well as ferromagnetic resonance.

The basic structure of a voltage transformer is very similar to that of a transformer. It also has two windings, one called the primary winding and the other called the secondary winding. Both windings are installed or wound on the iron core. There is insulation between the two windings and between the winding and the iron core, which provides electrical isolation between the two windings and between the winding and the iron core. When the voltage transformer is in operation, the primary winding N1 is connected in parallel to the line, and the secondary winding N2 is connected in parallel to the instrument or relay. Therefore, when measuring the voltage on high-voltage lines, although the primary voltage is high, the secondary voltage is low, which can ensure the safety of operators and instruments.

 

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