How current transformers work
The current transformer is a simple component that can accurately measure the AC current, which is made according to the principle of the magnetic effect of the current.
The main use of current transformers is to convert the large current in the AC circuit into a small current of a certain proportion (in my country, the standard is 5 amps), for accurate measurement and relay protection purposes. Everyone should know that in the process of power generation, transformer, power transmission and distribution, and power distribution equipment, due to the difference in power consumption equipment, the current generally ranges from tens of amps to tens of thousands of amps, and this circuit There will also be high pressure. Then in order to be able to monitor and measure the circuits of these routes, and at the same time to deal with the risks of high voltage and high current, current transformers are needed at this time. Some people may have seen the clamp meter used by electric welders. It is a device used to accurately measure AC current. Its 'clamp' is a feed-through current transformer.
Current transformers can be used to extend the measuring range of AC ammeters. In application, its primary coil should be connected in series with the load route of the measured current, and the secondary electromagnetic coil should be connected in series with the ammeter to form a closed loop, as shown in the circuit diagram on the right side of the figure.
Because I1/I2=Ki (Ki is called the transformation ratio) so I1=KiI2
For safety reasons, one end of the secondary coil of the current transformer and the shell must be grounded.