Current Transformer: Basics
A current transformer is a type of instrument transformer used to step down large values of current on the primary side to a manageable level of secondary current proportional to the amount of current flowing through the primary. When you see a CT with 800:5 ratio, it means the circuit is operating in the range of 0 to 800 Amps on the primary side and it would step the current down proportionally to the range 0 to 5 Amps for the devices on the secondary side. The output from the secondary side of a current transformer is usually used for operating measuring devices like ammeters and protective devices like relays. The current transformer provides electrical isolation for the measurement and protective devices on the secondary side as these devices are insulated away from the high-voltage and current on the primary side. Working Principle The working principle of the current transformer is the same as that of the voltage transformer it contains a primary and a secondar