The miniature current transformer occupies an important position in the power supply system. Its basic structure is composed of iron core, primary winding, secondary winding, terminal and insulating support. The primary winding of the current transformer has few turns and is connected in series in the circuit to be tested. For a cross-core current transformer, the line to be tested passes through the transformer, and P1 enters P2 out. The greater the measured current, the fewer turns it passes.
Based on the analysis of the function and structure of the miniature current transformer, the primary winding is connected in series with a few turns (one or more turns) in the circuit. Therefore, the current of the primary winding is completely dependent on the current of the circuit under test, and has nothing to do with the secondary current. Under normal circumstances, the coil impedance of the AC ammeter or current relay connected to the secondary winding of the transformer is very small, so the secondary circuit of the transformer is close to a short circuit.
Based on the structural characteristics of the micro current transformer, it is worth noting that the secondary side of the current transformer in the normal working state must not be allowed to open, because once the secondary side is opened, the secondary circuit impedance is infinite, and the secondary current is equal to zero, then the current It is the excitation current, the high-voltage secondary winding, and the people and equipment that directly endanger the safety of the secondary side. Therefore, it is not allowed to install a fuse on the secondary side of the current transformer to prevent the fuse from burning the secondary side.
When using a miniature current transformer, you must first ensure that the range meets the requirements. Once the measured current exceeds the measurement range of the ammeter, the AC ammeter must be replaced with a higher measurement range and a matching current transformer.
In addition, in practical applications, it is also necessary to ensure that the iron core and the secondary side of the miniature current transformer must be reliably grounded to prevent accidental electric shock to the iron core. Once the insulation of the primary side fails, the secondary side will enter high voltage, which directly threatens the personal safety of the secondary side and causes equipment damage.