电流互感器原理是依据电磁感应原理的。电流互感器是由闭合的铁心和绕组组成。它的一次绕组匝数很少，串在需要测量的电流的线路中，因此它经常有线路的全部电流流过，二次绕组匝数比较多，串接在测量仪表和保护回路中，电流互感器在工作时，它的2次回路始终是闭合的，因此测量仪表和保护回路串联线圈的阻抗很小，电流互感器的工作状态接近短路。
The principle of current transformer is based on the principle of electromagnetic induction. Current transformer is composed of closed core and winding. The number of primary winding turns is very small, which is connected in the circuit of current to be measured. Therefore, it often has all current flowing through the circuit. The number of secondary winding turns is relatively large. It is connected in series with the measuring instrument and the protection circuit. When the current transformer works, its secondary circuit is always closed, so the measuring instrument and the protection circuit are in series. The impedance of the coil is very small, and the working state of the current transformer is close to short circuit.
公式V/100=X/5
Formula V/100 = X/5
电流互感器电流比 100/5 ：
Current transformer current ratio 100/5:
是指一次电流和二次电流的比值，100/5＝20（倍），实际用电量就是电度表的读数&TImes;20 。
It refers to the ratio of primary current to secondary current, 100/5 = 20 (times). The actual power consumption is the reading of the watt-hour meter - TImes; 20.
即：连接5安电流表，读数&TImes;20 。
Namely: connect 5 ampere ammeter, reading & TImes; 20.