The accuracy levels of the three-phase current transformers are 0.5 for accurate measurements such as electricity meters, 1.0 for general switchboard instrumentation and 3.0 for non-accurate requirements. When using current transformers, certain guidelines need to be noted.
1, three phase one current transformer wiring should comply with the series connection guidelines, that is, the primary winding resistance should be in series with the circuit being measured, the secondary winding resistance should be in series with all the instrument load.
According to the size of the current being measured, the need to choose the appropriate change, or the error will become large. One end of the secondary side must be earthed to avoid damage to the insulation when the primary side high voltage runs into the secondary low voltage side, forming accidents to people and equipment. The primary side open circuit makes the secondary side voltage up to several hundred volts, once touched will form an electric shock incident. Therefore, the second side of the three-phase current transformer is equipped with a short-circuit switch to avoid an open circuit on the primary side.
In the use of the process, the secondary side once the open circuit should be immediately removed from the circuit load, and then, then stop processing. Everything can be used again only after processing.
2, three phase one current transformer secondary side is not open circuit, because once the open circuit, the primary side of the current all become magnetized current, easy to form the core over-saturation magnetization, heat serious and even burn the coil. At the same time, the magnetic circuit is over-saturated magnetization, easy to make the error increase.
Three phase one current transformer in normal operation, the second side of the approximate short circuit. If suddenly become open circuit, the excitation electromotive force by the value of very small suddenly become large, the magnetic flux in the core presents a serious saturation of the flat top wave, and thus the secondary side of the winding resistance will be inducted in the magnetic through zero when a very high spike wave, the value can reach thousands or even tens of thousands of volts, endangering the safety of staff and the insulation function of the instrument.
The above-mentioned guidelines on the use of three-phase integrated current transformer we will introduce here, hope to help you.
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