How To Use A Current Transformer

What is it for?

Convert high current → to 5A or 1A low current for use with ammeters, watt-hour meters, and protection devices.

2. How to install and use (most critical)

Primary side (how to pass the main line)

Pass the live wire to be tested through the central hole of the current transformer

Pass 1 turn: This refers to the transformation ratio on the nameplate, such as 100/5A

Convert the number of turns proportionally

② Secondary side (How to connect the meter)

Transformer markings typically include: K1 / S1 and K2 / S2

S1 → Connect to the power meter's incoming line

S2 → Power meter outlet line

Finally, S2 must be grounded!

3. Three Life-Saving Rules (Must Remember)

R1: "Chūnichō" must be translated as "immature."  

Original: Operating in progress, the secondary side must never be left open-circuited!  

Translation:!

Opening a circuit can generate high voltage, which is extremely dangerous.

S2 must be reliably grounded to prevent electric shock.

When connecting the electric meter, the polarity must not be reversed, otherwise the meter will rotate backward or stop working.

4. Summary in one sentence

The main line passes through the center, S1S2 connects to the meter, S2 is grounded, and open circuits are strictly prohibited!