The role of the transformer is to reduce the AC voltage and high current proportionally to the value that can be directly measured by the meter, which is convenient for people to use the meter to directly measure, and at the same time provide power for the relay protection and automatic devices. How to choose a current transformer is a problem worthy of people's attention. The correct choice can complete the work more efficiently and safely. Once the wrong choice is made, the staff will waste too much time on the same task, and serious conditions will endanger life and safety. . Generally follow three principles:
1) According to the size of the measured current, select the rated current ratio of the current transformer, that is, make the rated current of the primary side of the current transformer greater than the measured current, and the rated voltage is adapted to the line voltage used
2) The AC current meter used with the current transformer should select a range of 5A;
3) The power consumed by the measuring instrument should not exceed the rated capacity of the current transformer.
Select current transformer according to the above three items to ensure a certain measurement accuracy. 2, 3 is relatively easy to do. Mainly the first "the rated current of the primary side of the current transformer is greater than the measured current". The normal power load is stable and there is no or little change, so this choice is reasonable. But in our real life and industrial production, the power load is not stable and the range of change is very large, so how to choose a current transformer in this situation, so that the error value of the transformer is reduced as much as possible, As far as the instrument is concerned, a wide range of current fluctuations will cause an increase in measurement error.