Knowledge
The meaning of primary current and secondary current
Article Source：Kinri Energy | Author：Kinri Energy | Issuing Time：2024.05.27
In science, the amount of electricity passing through any cross-section of a conductor per unit time is called the current intensity, usually represented by the letter I. The free charge in a conductor undergoes regular directional motion under the action of electric field force to form current, which is divided into alternating current and direct current.
AC current refers to the periodic changes in both magnitude and direction, and common wall mounted appliances use AC power for civilian use. The direction of direct current does not change over time, and the portable external power supply we usually carry with us provides direct current.
The primary current often refers to the current of the input side coil of the transformer, and the secondary current often refers to the current of the output side coil of the transformer. If it is a transformer, the primary current refers to the current flowing through the transformer in the main circuit, and the secondary current refers to the current drawn out from the secondary winding of the transformer.
The calculation method for the primary and secondary currents of transformers is as follows:
The calculation formula for three-phase transformer current I=S/(radical 3 * U), where U is the line voltage of the transformer (KV), S is the apparent power (KVA) of the transformer.
Transformer current empirical port algorithm:
The primary current I ≈ S * 0.06, and the secondary current I ≈ S * 1.5.
Assuming a 500KVA transformer is 10/0.4, calculate the primary and secondary currents as follows:
Substituting the current formula I=S/(root sign 3 * U) into it, I=500/root sign 3 * 10=500/17.32 ≈ 28.8A, I=500/radical 3 * 0.4=500/0.69=724.6A.
Using the empirical calculation method of transformer current, I=500 * 0.06 ≈ 30A, I=500*1.5=750A.
Current transformers usually use L1 on the primary side L2 represents, and S1 is used for the secondary side S2 indicates that the circular hole in the middle of the low-pressure through center flow is the primary side, and the screw next to the circular hole is the secondary side. The busbar in the middle of the high-voltage current transformer is on the primary side, and the wiring terminals of the fixed base are on the secondary side.
The measurement calculation is as follows:
Assuming the primary current of the current transformer is I1, the secondary current is I2, and the transformation ratio is K. So I1=K * I2.
If the secondary current is 2A and the transformation ratio is 20, then the primary current I1=2 * 20=40A.
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