Explain in detail why the current transformer cannot operate in an open circuit
There are many kinds of current transformers, and the most commonly used are electromagnetic current transformers, which can be divided into measuring current transformers and protective current transformers. Of course, such current transformers cannot be operated in open circuit. . The structure of electromagnetic current transformer is somewhat similar to that of general power transformers. It is also composed of iron core and coil. The difference between them is that the primary coil of current transformer is high current, high voltage, secondary coil and low voltage measuring instrument or relay. The current coils are connected, and the transformer is close to a short-circuit state. The secondary circuit of the current transformer should not be opened when it is running, because when the current transformer is in normal operation, its primary magnetic potential and secondary magnetic potential are balanced with each other, the magnetic potential of the excitation is very small, and the magnetic density in the iron core is very small. And the induced electromotive force in the secondary coil is not high. If the secondary coil is open, the primary magnetic potential is all used for excitation, the iron core will be deeply saturated, the magnetic density will increase to a flat-top state, and the open-circuit secondary coil will generate a waveform that is a sharp top. The induced electromotive force with high wave amplitude means that the secondary coil will generate high overvoltage, and this high voltage will cause great danger to electrical equipment and personal safety. At the same time, due to the open circuit of the secondary circuit, the iron core will be seriously saturated, resulting in overheating, and the current transformer will be burned. Therefore, during operation, the secondary circuit of the current transformer must never be opened.