The role of voltage transformer and current transformer

The high voltage proportional relationship to transform the 100 v or lower level standard secondary voltage, for the use of protection, measurement and instrumentation. At the same time, the use of voltage transformer can be high voltage and electrical isolation. Although also be in accordance with the working principle of electromagnetic induction voltage transformer equipment, but its electromagnetic structure compared with the current transformer is just the opposite. Voltage transformer secondary circuit is high impedance circuit, the size of the secondary current is decided by the impedance of the loop. Secondary load impedance, small secondary current increase, makes a in a component of current automatically to meet electromagnetic balance of the relationship between the primary and secondary side. A voltage transformer is, as it were, structure and using a limited form of special transformer. Electromagnetic single phase motor current transformer is widely used in power system (hereinafter referred to as "current transformer"), its working principle is similar to the transformer. 

The principle of current transformer wiring, as shown on the left. The characteristics of the current transformer is: (1) a coil in series in the circuit, and as a result, the number of turns in a coil current depends on the load current of the circuit under test. And has nothing to do with the secondary current; (2) current transformer secondary coil of the current meter and relay to the coil impedance is 220v 1.5kw ac motor very small, so under normal circumstances, current transformer run in to a short-circuit condition. The ratio of the current transformer primary and secondary rated current, called the rated mutual acmotortrading.blogspot.com inductance of the current transformer ratio: kn = I1n/I2n Because of one coil rated current I1n standardization, secondary coil rated current I2n unification of 5 (1 or 0.5), so the rated mutual inductance current transformer ratio have also been standardized. Kn can be approximately expressed as transformer primary and secondary winding turn ratio, namely the kn material kn = N1 N2 / type of N1, N2, for one, two coil number of turns.