What is the purpose of current transformer

Current transformers are very similar to transformers. Transformers are mainly used to change the voltage of the line on the line, while current transformers are connected to the line and are mainly used to change the current of the line. Therefore, the current transformer was also called a converter before. Later, the instruments and equipment that generally convert direct current into alternating current are called converters.

The electrical appliances that change the size of the current on the line are called current transformers based on the working principle of the current transformer.
Why is a variable current required on the line? This is because according to the different situations of power generation and electricity consumption, the current on the line varies greatly, and the difference is very large, some are only a few amperes, and some are as large as tens of thousands of amperes. To directly measure these large and small currents, it is necessary to make many ammeters and other electrical instruments ranging from a few amperes to tens of thousands of amperes according to the size of the line current. This will bring great difficulties to instrument manufacturing. In addition, some lines are high-voltage, such as high-voltage power transmission lines such as 220,000 volts or 10,000 volts. It is extremely dangerous to directly measure the current on the high-voltage line with electrical instruments, and it is absolutely not allowed.

If the current transformer is connected to the line to change the current, then the large and small currents on the line can be unified into currents of similar size according to different proportions. As long as an electrical instrument with a current specification, such as a general electrical instrument with a current of 5A, can be used to measure currents as small as a few amperes and as large as tens of thousands of amperes on the line through a current transformer. At the same time, the basic structure of a current transformer is very similar to that of a transformer. It also has two windings, one is called the primary winding or the primary winding; the other is called the secondary winding or the secondary winding. There is insulation between the two windings, so that there is electrical isolation between the two windings. When the current transformer is running, the primary winding W1 is connected to the secondary winding W2 on the line and the electrical instrument is connected. Therefore, when measuring the current on the high-voltage line, although the primary voltage is very high, the secondary voltage is very low. Safety.
It can be seen that the current transformer can not only change the currents of different sizes on the line into a certain size current for measurement, but also can isolate the line to ensure the safety of operators and instruments.