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Why should the transformer silicon steel core be coated with insulating varnish?

2021-03-04

        If we look closely at generators, motors and transformers, we can see that their iron cores are not a single piece of metal, but are made of many thin silicon steel sheets coated with insulating paint. Why use thin silicon steel sheets, and why do you need to apply insulating paint? What are their functions? Here is an answer for everyone.

                

        The outside of the iron core of the transformer is a coil. When the alternating current passes through the coil, the magnetic flux passing through the iron core changes with time. It generates an induced electromotive force in the iron core, thereby generating eddy currents. These eddy currents cause the iron core to generate a lot of heat, waste a lot of electrical energy from the sliding contact line, and may damage the electrical appliances. In severe cases, the iron core may even be heated and melted locally, causing the iron core to "fire". Therefore, we must find a way to reduce the eddy current, one of the ways is to increase the resistivity of the core material.

                      

        Therefore, after the transformer core is coated with insulating varnish, it is divided into a lot of small cross-section conductors, so that its resistance becomes larger, the eddy current is confined in the narrow sheet, and the magnetic flux passes through the narrow sheet. In the cross section, the net electromotive force in these loops is small, the length of the loop is large, the resistance of the loop is large, and the eddy current is greatly weakened. Therefore, although the iron core coated with insulating paint also has eddy current loss (which is part of the iron loss), it is also much smaller. In this way, safety and high efficiency can be achieved by applying insulating paint.

        Nippon Steel's core production mainly uses silicon steel as raw materials. For 25 years, it has been focusing on the manufacturing and research and development of transformers, transformers, sensors and other cores, providing high-quality cores for more than 3,000 corporate customers around the world. If you are interested in Japan Steel, please pay attention to Foshan Nanhai Silicon Steel Core Manufacturing Co., Ltd.!


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