Current transformer composite iron core with stable performance

Abstract

The utility model relates to a current transformer composite iron core with stable performance, which is provided with an amorphous iron core and a silicon steel iron core, the silicon steel iron core is arranged on the outer side of the amorphous iron core, the silicon steel iron core and a single-side protection box jointly form an annular groove structure with an upward notch, the amorphous iron core is embedded in a groove of the annular groove structure, the longitudinal section of the single-side protection box is in an L-shaped ring shape, and the single-side protection box is arranged in the annular groove structure. Comprising an inner protection plate and a lower protection plate, the inner protection plate is in a cylindrical shape matched with the inner side face of the amorphous iron core and located on the inner side of the amorphous iron core, the lower protection plate is in a planar ring shape matched with the lower surface of the amorphous iron core and located on the lower side of the amorphous iron core, and a glue injection surface layer formed by glue injection is arranged on the top face of the amorphous iron core. The top face of the glue injection surface layer is flush with the top face of the silicon steel iron core and the top face of the single-side protection plate, and the top face of the composite iron core is jointly formed. The structure of the iron core of the current transformer is improved, the window area of the iron core is reduced under the condition that the electromagnetic performance requirement is guaranteed, and the production cost is reduced.

Description

Technical Field

[0001] This utility model relates to a composite iron core for a current transformer with stable performance. Background Technology

[0002] Amorphous iron cores are commonly used in current transformers. Based on their mechanical properties, they are typically embedded in a double-sided protective box with an annular groove structure, and a sealing cover is placed at the groove opening to enclose the amorphous iron core within the protective box, preventing mechanical damage and the escape of debris after damage. For example, Chinese patent document CN119252638A discloses an amorphous alloy assembly method for current transformers. This method involves rolling an amorphous alloy core, subjecting it to vacuum thermal radiation heat treatment annealing, and then assembling it within an alloy steel protective shell with an annular groove structure. The end faces are covered with rigid insulating plates. The manufacturing process for this product structure is relatively complex. In particular, due to the electromagnetic properties of amorphous iron cores, a large window area is required to meet the protection ratio requirements of the transformer (e.g., 10 times). This not only hinders cost reduction but also, under certain transformer volume constraints, often makes it difficult to guarantee sufficient main insulation distance, affecting power frequency withstand voltage and making it difficult to meet the technical requirements for partial discharge. Utility Model Content

[0003] The purpose of this invention is to improve the structure of the current transformer core, so as to reduce the core window area and reduce production costs while ensuring electromagnetic performance requirements.

[0004] The technical solution of this utility model is: a current transformer composite core with stable performance, which is provided with an amorphous iron core and a silicon steel core. The silicon steel core is located outside the amorphous iron core and together with the single-sided protective box, forms an annular groove structure with the groove opening facing upward. The amorphous iron core is embedded in the groove of the annular groove structure.

[0005] Preferably, the single-sided protective box is an annular shape with an L-shaped longitudinal section, including an inner protective plate and a lower protective plate. The inner protective plate is cylindrical in shape conforming to the inner side of the amorphous iron core and is located inside the amorphous iron core. The lower protective plate is a planar annular shape conforming to the lower surface (bottom surface) of the amorphous iron core and is located below the amorphous iron core.

[0006] Preferably, the inner side of the amorphous iron core is fitted with the outer side of the inner protective plate and is constrained by the inner protective plate, and the lower surface of the amorphous iron core is fitted with the upper surface of the lower protective plate and is constrained by the lower protective plate.

[0007] Furthermore, the outer surface of the amorphous iron core is in contact with the inner surface of the silicon steel core and is constrained by the silicon steel core.

[0008] Preferably, the single-sided protective box is welded from an inner protective plate and a lower protective plate or integrally formed by pressure forming.

[0009] Preferably, the single-sided protective box is made of non-magnetic metal material.

[0010] Preferably, the single-sided protective box is made of austenitic stainless steel, such as 304 stainless steel or 316 stainless steel.

[0011] Preferably, the annular groove structure is filled with adhesive by injection.

[0012] Preferably, the adhesive is epoxy resin.

[0013] Preferably, the top surface of the amorphous iron core is provided with a glue-filled surface layer formed by glue injection. The top surface of the glue-filled surface layer is flush with the top surface of the silicon iron core and the top surface of the single-sided protective plate (the top surface of the inner protective plate) (located in the same plane), together forming the top surface of the composite iron core.

[0014] The beneficial effects of this invention are as follows: Due to the composite structure of the amorphous iron core and the silicon steel core, it combines the electromagnetic performance advantages of both. With the same window area, it is equivalent to a simple amorphous iron core, significantly improving the protection factor while meeting the measurement accuracy requirements under normal conditions. Furthermore, under certain protection factor requirements, it helps to reduce the window area, avoiding the limitation on the main insulation distance and the increased manufacturing cost caused by an excessively large window area. Since the single-sided protective box and the silicon steel core together form the annular groove structure for protecting the amorphous iron core, it allows the amorphous iron core to be assembled onto the single-sided protective box first, and then the single-sided protective box with the amorphous iron core assembled with it to the silicon steel core. This reduces the assembly difficulty of the amorphous iron core, thereby reducing process costs and helping to reduce or avoid damage to the amorphous iron core during assembly. By applying epoxy resin potting to the assembled amorphous iron core, along with the single-sided protective casing and silicon steel core, effective mechanical and chemical protection is achieved for the amorphous iron core. This eliminates the need for an insulating cover plate on the annular groove structure, improves insulation performance, reduces vibration and noise, and ensures stable operation even in harsh environments. Attached Figure Description

[0015] Figure 1 This is a longitudinal section schematic diagram of the present invention;

[0016] Figure 2 Is with Figure 1 The corresponding top view structural diagram,

[0017] The markings in the diagram are: 1. Amorphous iron core; 2. Stainless steel lining; 3. Epoxy resin surface layer; 4. Silicon steel core. Detailed Implementation

[0018] See Figure 1 and Figure 2This composite iron core is a wound core with a circular or other desired annular cross-section. The amorphous iron core 1 is embedded in an annular groove structure (which can be called a shell) composed of a stainless steel liner 2 and a silicon steel core 4. Epoxy resin is injected into the amorphous iron core to fill the gaps within it, bonding the amorphous iron core into a single unit. This bonding also integrates the amorphous iron core with the stainless steel liner and the silicon steel core. The epoxy resin surface layer 3 formed on the amorphous iron core after injection is flush with the top surfaces of the silicon steel core and the stainless steel liner, together forming the upper surface of the composite iron core. The winding of the amorphous iron core and the silicon steel core can be achieved using any suitable existing technology or other suitable technologies.

[0019] The stainless steel liner is made of austenitic stainless steel (e.g., 304, 316), which is non-magnetic, and serves as a single-sided protective box for the amorphous iron core. The stainless steel liner is annular with an L-shaped longitudinal section. It includes an inner protective plate located on the inner side (radially inner side) of the amorphous iron core and a lower protective plate located on the lower side (bottom side) of the amorphous iron core. The inner protective plate is cylindrical, conforming to the inner surface of the amorphous iron core, with its top slightly higher than the top of the amorphous iron core and aligned with the top of the silicon steel core (located on the same plane). Its outer surface is in contact with the inner surface of the amorphous iron core. The lower protective plate is a planar annular shape conforming to the lower end face of the amorphous iron core. Its outer edge (radially outer edge) is adjacent to the inner surface of the silicon steel core, and its upper surface is in contact with the bottom surface (lower surface) of the amorphous iron core. After assembling the stainless steel liner (or other forms of single-layer protective boxes, hereinafter the same) onto the silicon steel core, the connection between the stainless steel liner and the silicon steel core can be achieved by spot welding with a laser welding machine.

[0020] The stainless steel liner (the thickness of the steel plate used) is 1.5 mm thick. It can be made by welding together tubing of suitable shape and size (corresponding to the inner liner) and flat plates of suitable shape and size (corresponding to the lower liner). Alternatively, the entire liner can be formed in one piece by stamping using a mold.

[0021] The windows of silicon steel cores (window area, and, when appropriate, window shape, the same below) and amorphous iron cores can be flexibly set or adjusted according to actual needs to effectively reduce the composite iron core buffer layer, increase the effective distance of the main insulation, and improve the power frequency withstand voltage and partial discharge level of the current transformer.

[0022] The assembled liner, amorphous iron core, and silicon steel core undergo high-temperature annealing. The annealing process consists of three stages: heating, holding, and cooling. During the heating process, to prevent uneven heating of the shell composed of silicon steel and stainless steel liner, which could lead to deformation, the heating rate is controlled at 120℃ / hour, uniformly raising it to 800℃. Holding at 800℃ for 2 hours is used to eliminate stress and restore the magnetic domain structure. Then, the temperature is slowly lowered to avoid thermal deformation and stress in the iron core. The cooling rate is controlled at 60℃ / hour, and the core is allowed to cool naturally in the furnace to 450℃ before being removed from the furnace. After cooling to 40℃, vacuum impregnation is performed, followed by baking in an oven at 135℃ for 3 hours.

[0023] After the amorphous iron core is wound, it is subjected to vacuum annealing treatment. The temperature is raised from room temperature to 550℃ at a constant rate, held for 2 hours, cooled by a fan to 350℃, and then allowed to cool naturally to below 40℃ before being placed into a shell composed of silicon steel and stainless steel lining.

[0024] The height of the amorphous iron core is 3 mm less than that of the silicon steel core and the single-sided protective box (liner). For the assembled silicon steel core, stainless steel liner and amorphous iron core (after annealing), epoxy resin is used to pot the amorphous iron core. The epoxy resin completely penetrates into the interlayer of the amorphous iron core and forms a layer on the top surface of the amorphous iron core. This layer can be called the epoxy resin surface layer or potting surface layer, and its height is the same as that of the silicon steel core.

[0025] The amorphous iron core is coated with epoxy resin using methods such as liquid silicone rubber vulcanization molding or APG pressure molding. Since the top surface of the amorphous iron core is slightly lower than the inner liner and the silicon steel core, the epoxy resin coating not only densely fills the internal gaps of the amorphous iron core, but also creates an epoxy resin surface layer on the top surface of the amorphous iron core. The top surface of this epoxy resin surface layer is aligned with the top surfaces of the silicon steel core and the stainless steel inner liner, forming the top surface of the composite iron core in the corresponding area. Epoxy resin coating effectively eliminates vibration and noise from the amorphous iron core and isolates it from external corrosive gases, thus resolving the impact of excessive coil stress on the output accuracy and protection factor of the current transformer.

[0026] Based on the respective properties of amorphous iron cores and silicon steel cores, amorphous iron cores are mainly used to meet normal measurements and ensure measurement accuracy within the normal range; silicon steel cores are mainly used to meet protection multiple requirements and reduce or avoid the negative impact caused by abnormal primary current.

[0027] This composite core has the following characteristics:

[0028] In terms of electrical performance, the high initial permeability and low saturation magnetic flux density of the amorphous iron core are utilized to meet the measurement accuracy of the instrument, while the low initial permeability and high saturation magnetic flux density of silicon steel are utilized to meet the requirements of small current measurement. In the event of a short circuit or ground fault, the composite iron core ensures sufficient power output of the secondary current according to the change of the primary current, which meets the measurement and reliable operation of the relay protection device and improves the reliability of power supply.

[0029] Stainless steel lining can increase strength, protect amorphous iron core from stress, reduce deformation of silicon steel core, effectively reduce the buffer layer of composite iron core, increase the effective distance of main insulation, and improve the power frequency withstand voltage and partial discharge level of current transformer.

[0030] The problem of excessive stress on the coil, which in turn affects the output accuracy and protection factor of the current transformer, was solved in the liquid silicone rubber vulcanization molding process and APG pressure molding process.

[0031] Actual data shows that, through this improvement, while achieving the same 10 times the compliance rate, the production cost of this composite core can be reduced by up to 50% compared to existing amorphous cores.

[0032] The descriptions of directions such as up, down, top, and bottom in this manual are only used to describe the relative positional relationship between related parts and structures, and are unrelated to other parts and structures, nor do they constitute any limitation on the orientation during actual use.

[0033] Unless otherwise specified, the preferred and optional technical means disclosed in this utility model can be arbitrarily combined to form several different specific embodiments when one preferred or optional technical means is a further limitation of another technical means.

Claims

1. A stable current transformer composite core, comprising an amorphous core, characterized in that... It also includes a silicon steel core, which is located outside the amorphous iron core and together with the single-sided protective box, forms an annular groove structure with the groove opening facing upwards. The amorphous iron core is embedded in the groove of the annular groove structure.

2. The composite iron core of the current transformer as described in claim 1, characterized in that... The single-sided protective box is an L-shaped ring with a longitudinal section, including an inner protective plate and a lower protective plate. The inner protective plate is cylindrical and conforms to the inner surface of the amorphous iron core, located inside the amorphous iron core. The lower protective plate is a planar ring conforms to the lower surface of the amorphous iron core, located below the amorphous iron core.

3. The composite iron core of the current transformer as described in claim 2, characterized in that... The inner surface of the amorphous iron core is in contact with the outer surface of the inner protective plate and is constrained by the inner protective plate. The lower surface of the amorphous iron core is in contact with the upper surface of the lower protective plate and is constrained by the lower protective plate.

4. The composite iron core of the current transformer as described in claim 3, characterized in that... The outer surface of the amorphous iron core is in contact with the inner surface of the silicon steel core and is constrained by the silicon steel core.

5. The composite iron core of the current transformer as described in claim 1, characterized in that... The single-sided protective box is made by welding the inner protective plate and the lower protective plate together or by integral molding through pressure forming.

6. The composite iron core of the current transformer as described in claim 1, characterized in that... The single-sided protective case is made of non-magnetic metal material.

7. The composite iron core of the current transformer as described in claim 6, characterized in that... The single-sided protective box is made of austenitic stainless steel.

8. The composite iron core of the current transformer as described in any one of claims 1-7, characterized in that... The annular groove structure is filled with adhesive by injection.

9. The composite iron core of the current transformer as described in claim 8, characterized in that... The adhesive is epoxy resin.

10. The composite iron core of the current transformer as described in claim 8, characterized in that... The top surface of the amorphous iron core is provided with a glue-filled surface layer, which is flush with the top surface of the silicon iron core and the top surface of the single-sided protective plate, together forming the top surface of the composite iron core.

Images