What are the classifications of transformer cores in power supply and distribution systems?

The core of the transformer is mainly divided into two types in the power supply and distribution system: voltage transformer and current transformer. The function of the current transformer is to convert the primary current with a larger value into a secondary current with a smaller value through a transformation ratio, which is used for protection, measurement and other purposes. For example, a current transformer with a transformation ratio of 400/5 converts the actual current of 400A into a current of 5A.

The iron core plays an important role in the transformer. According to the measurement accuracy level requirements of the transformer, different soft magnetic materials can be selected as the core material. The higher the magnetic permeability or various performance requirements of the iron core, the smaller the measurement error of the transformer and the higher the accuracy. At present, the commonly used material is silicon steel sheet. The iron core of the current transformer mainly includes laminated iron core and wound iron core. The ring-shaped iron core is suitable not only for electronic transformers, but also for transformers because of its advantages such as no air gap, high magnetic permeability, low loss, less noise, and strong anti-interference. It is made of cold-rolled oriented silicon steel material that is continuously wound. The diameter, height, and width ratio of the toroidal transformer core can be changed at will as required.

At the same time, in order to protect the transformer core, it is necessary to pay attention to the following: because the working principle of the current transformer is equivalent to a transformer with a short circuit on the secondary side, it is used to convert current, and an ammeter is connected to the secondary side to measure the current. During the operation of the transformer, after the secondary side is open, the primary current remains unchanged, and the secondary side current is equal to zero, then the demagnetizing flux generated by the secondary current also disappears. At this time, the primary current is completely converted into an excitation current, which saturates the transformer core, increases the magnetic flux unprecedentedly, increases the core loss, generates high heat, damages the insulation, generates residual magnetism in the core, etc., increases the ratio difference and angle difference of the transformer, loses accuracy, or endangers the personal safety of the operator, etc. Therefore, in order to protect personal safety, the performance of the core, etc., the secondary side of the current transformer is not allowed to be open.