An adjustable high-current generator based on an autotransformer

Abstract

This utility model relates to an adjustable high-current generator based on an autotransformer, comprising an autotransformer body (1), an annular iron core (2) on the autotransformer body (1), several turns of adjustable coil (3) wound on the annular iron core (2), a voltage adjustment knob (4) rotatably mounted on the autotransformer body (1), a sliding contact (5) on the voltage adjustment knob (4) cooperating with each adjustable coil (3), several turns of fixed coil (6) wound on the annular iron core (2), one end of the fixed coil (6) connected to one end of the adjustable coil (3) according to polarity, and the other end forming the primary coil with the coil between the sliding contact (5), and a low-voltage high-current secondary coil (7) wound on the annular iron core (2). It simplifies the structure of existing high-current generators, is smaller in size and lighter in weight, easier to transport, has a wider current adjustment range, lower cost, and can meet diverse use and testing needs.

Description

Technical Field

[0001] This utility model relates to electrical equipment, specifically to an adjustable high-current generator based on an autotransformer. Background Technology

[0002] A high-current generator is an electrical device capable of producing high current at low voltage, and is one of the commonly used devices in power systems for relay protection. The core of a high-current generator is a step-up transformer (the inverse application of a current transformer), whose working principle is based on Faraday's law of electromagnetic induction and the relationship between transformer current transformation. Let the input current be I1, with N1 winding turns; and the output current be I2, with N2 winding turns.

[0003] Then I2 = (N2 / N1) × I1

[0004] By adjusting the input / output winding turns ratio N1 / N2, different levels of current can be obtained on the output side. For example, when N1 / N2 = 100 / 1, the output current can reach 100 times the input current.

[0005] The main applications of high-current generators include providing instantaneous overcurrent protection for switches in relay protection devices and simulating bypass current flow during bypass operations in real power distribution networks. It first regulates the voltage using an autotransformer, then uses a step-up transformer to generate a low-voltage, high-current signal, thereby simulating the current environment the device might experience in actual operation.

[0006] Existing high-current generators offer certain convenience when used in fixed locations such as laboratories. However, their large size and weight make them inconvenient to move, especially when conducting on-site testing on immobile electrical equipment. Furthermore, they suffer from drawbacks such as a limited current adjustment range and high cost, making it difficult to meet diverse application and testing needs. Summary of the Invention

[0007] The purpose of this invention is to provide an adjustable high-current generator based on an autotransformer that is small in size and light in weight, easy to transport, has a wide current adjustment range, lower cost, and can meet diverse use and testing needs.

[0008] The technical solution of this utility model is as follows: It includes an autotransformer body, an annular iron core on the autotransformer body, several turns of adjustable coil wound on the annular iron core, a voltage adjustment knob rotatably mounted on the autotransformer body, a sliding contact on the voltage adjustment knob that slides and engages with each adjustable coil, several turns of fixed coil wound on the annular iron core that do not contact the sliding contact, one end of the fixed coil is connected to one end of the adjustable coil according to polarity, the other end of the fixed coil and the coil between the sliding contact constitute the primary coil, and a low-voltage, high-current secondary coil is wound on the annular iron core.

[0009] The technical advantages of this invention are: it simplifies the structure of existing high current generators, making them smaller, lighter, and easier to transport; it has a wider current adjustment range and lower cost, and can meet diverse usage and testing needs.

[0010] advantage:

[0011] 1. Compared with existing conventional high-current generators consisting of autotransformers and step-up transformers, it is smaller, lighter, and easier to move;

[0012] 2. Its primary and secondary coils are isolated from each other, and the output voltage is within the safe voltage range for the human body, making it safer to use;

[0013] 3. Based on the original adjustable coil of the autotransformer, a fixed coil is added and connected in series with the original adjustable coil. By adjusting the voltage adjustment knob to change the number of turns of the primary coil, the secondary current can be adjusted, making operation more convenient.

[0014] 4. It can obtain a larger secondary induced current and a wider current adjustment range, and can also achieve stepless current adjustment. Attached Figure Description

[0015] Figure 1 This is a circuit schematic diagram of an embodiment of the present utility model;

[0016] Figure 2 This is a three-dimensional structural diagram of Embodiment 1 of the present utility model;

[0017] Figure 3 This is a three-dimensional structural diagram of Embodiment 2 of the present utility model. Detailed Implementation

[0018] Example 1, as Figure 1 , Figure 2 As shown, it includes an autotransformer body 1, an annular iron core 2 on the autotransformer body 1, several turns of adjustable coil 3 wound on the annular iron core 2, a voltage adjustment knob 4 rotatably mounted on the autotransformer body 1, a sliding contact 5 on the voltage adjustment knob 4 that slides and engages with each adjustable coil 3, several turns of fixed coil 6 wound on the annular iron core 2 that do not contact or engage with the sliding contact 5, one end of the fixed coil 6 being connected to one end of the adjustable coil 3 according to polarity, the other end of the fixed coil 6 and the coil between the sliding contact 5 forming the primary coil, and a low-voltage, high-current secondary coil 7 wound on the annular iron core 2.

[0019] The adjustable coil 3 is wound in a single layer around the entire toroidal core 2. The fixed coil 6 is located at one end of the adjustable coil 3 and is wound around the outside of the adjustable coil 3 and the toroidal core 2. An insulating layer 8 is provided between the fixed coil 6 and the adjustable coil 3 for phase insulation. The low-voltage, high-current secondary coil 7 is located at the position of the fixed coil 6 and is wound around the outside of the fixed coil 6, the adjustable coil 3 and the toroidal core 2 to avoid the low-voltage, high-current secondary coil 7 affecting the sliding contact 5 and the adjustable coil 5 for phase sliding contact.

[0020] The low-voltage, high-current secondary coil 7 is a thick wire wound around the outside of the fixed coil 6, and the outside of the low-voltage, high-current secondary coil 7 is wrapped with an insulating jacket 71 that is insulated and isolated from the fixed coil 6.

[0021] The section of adjustable coil 3 covered by fixed coil 6 cannot cooperate with sliding contact 5, thus acting as a part of fixed coil 6. In order not to affect the adjustable range of the primary coil, the number of turns of the subsequently wound fixed coil 6 needs to be reduced to meet the required ratio of the effective number of turns of adjustable coil 3 (the number of adjustable coil 3 turns that can cooperate with sliding contact) to the effective number of turns of fixed coil 6 (the number of turns of subsequently wound fixed coil 6 plus the number of adjustable coil 3 turns that cannot cooperate with sliding contact 5).

[0022] This high-current generator is a modification based on the existing autotransformer. Since the fixed coil 6 is wound around the outside of the original adjustable coil 3, it will cover part of the adjustable coil 3. The part of the covered adjustable coil 3 that mates with the sliding contact 5 needs to be properly insulated.

[0023] Example 2, as Figure 3 As shown, the difference from Embodiment 1 is that the adjustable coil 3 is wound in a single layer around most of the surface of the toroidal core 2, and the fixed coil 6 is wound in multiple layers around the other small parts of the surface of the toroidal core 2 outside the adjustable coil 3. The low-voltage, high-current secondary coil 7 is located at the position of the fixed coil 6 and wound around the outside of the fixed coil 6 and the toroidal core 2 to avoid affecting the cooperation between the sliding contact 5 and the adjustable coil 3.

[0024] This high-current generator is not a modification of an existing autotransformer. Its adjustable coil 3 and fixed coil 6 are wound at different positions on the toroidal iron core 2. The fixed coil 6 does not cover the adjustable coil 3, does not affect the sliding contact 5 and the sliding contact of the adjustable coil 3, and does not waste the effective number of turns of the adjustable coil 3.

[0025] The autotransformer body 1 is provided with a first terminal 11 and a second terminal 12 that are respectively connected to the two ends of the fixed coil 6 by wires. One end of the adjustable coil 3 is connected to the first terminal 11 by wires according to polarity. The autotransformer body 1 is provided with a third terminal 13 that is connected to the sliding contact 5 by wires. The third terminal 13 and the second terminal 12 constitute the primary side terminal.

[0026] The autotransformer body 1 is provided with two output terminals 14 and 15, which are respectively connected to the two ends of the low-voltage, high-current secondary coil 7, forming the secondary terminal.

[0027] Design and working principle:

[0028] To meet the experimental requirements and the need for a large output current on the secondary side, the secondary coil is constructed by winding a thick wire capable of carrying a large current around the transformer core. The primary coil is connected to a 220V power frequency voltage. By changing the contact position of the sliding contact with the adjustable coil using a voltage adjustment knob, the number of turns in the primary coil can be changed. Simultaneously, the induced voltage in the secondary coil will also change, thus achieving the purpose of adjusting the secondary voltage by adjusting the number of turns in the primary coil. When the resistance of the secondary coil is constant, the higher the secondary output voltage, the higher the output current.

[0029] The secondary coil is selected based on the required current. In the experiment, the cross-sectional area S of the secondary coil wire is 30 mm², the length L is 6 m, and the maximum current that can be passed is 150 A. The resistance is calculated using the formula... R = ρL / S The self-resistance of the secondary conductor, i.e., the resistance in the circuit, is 3.4 mΩ. This resistance value is the self-resistance of the secondary conductor and also the main resistance of the secondary circuit. (A copper conductor with a cross-sectional area of ​​30 mm² can meet the requirement of a stable 150A current flow over a long period, ensuring that the conductor will not melt due to overheating or the insulation jacket will fail during the experiment.)

[0030] The purpose of adding several turns of fixed coil to the adjustable primary winding of an autotransformer is to make the secondary voltage adjustable within a certain range, thereby making the secondary current adjustable. Let the number of turns in the adjustable coil be n, and the number of turns in the fixed coil be n1. When the input voltage is a constant AC 220 V, the more turns of the coil connected to the primary winding, the smaller the voltage induced in the thicker secondary conductor, i.e., the smaller the secondary current. Therefore, the maximum value of the secondary current I... 2max When only the fixed coil is working on the primary side, it occurs as follows:

[0031] I 2max =U1 / (n1×R)

[0032] in RBecause of the self-resistance of the secondary conductor, once the number of turns of the fixed coil is determined, the maximum value of the secondary current can also be determined. Increasing the number of turns of the primary adjustable coil connected to the circuit decreases the secondary current; when all adjustable coils are connected, the secondary current reaches its minimum value, i. 2max The expression is:

[0033] I 2min =U1 / [(n+n1)×R)]

[0034] It is evident that the range of changeable secondary current is limited by the number of turns of the primary adjustable coil connected to the circuit. The adjustment range of the number of turns of the primary coil determines the range of change of secondary current.

[0035] Taking a maximum secondary current of 150A as an example, i.e., i2=150A, U2=0.51V, then n`=U1 / U2≈432 turns. Therefore, the number of additional fixed coil turns required for series connection is 432 turns. The total number of turns is N=n+n` turns. When all 300 turns of the adjustable coil are connected to the primary side, the secondary current is: I2=U1 / (N×R)≈88.40A. In this case, the secondary current varies from 88.4A to 150A.

[0036] If the fixed coil is wound around the outside of the adjustable coil, preventing a portion of the adjustable coil from contacting the sliding contact, then the original adjustable coil can no longer be considered as the number of turns of the adjustable coil. 'n' still represents the original number of turns of the adjustable coil, but 'n' no longer represents the number of turns of the wound fixed coil; instead, it represents the number of fixed, unchangeable turns connected to the original side circuit, including the number of turns of the wound fixed coil, 'n'. c The number of turns n of the adjustable coil covered by the fixed coil b n a This indicates that the number of turns of the original transformer coil that is not covered can still be changed via contacts to determine whether it is connected to the primary side.

[0037] If n c Unknown, let n1 = n b =n c If I is the independent variable, then the maximum secondary current I 2max =U1 / (n1×R), minimum current I 2min =U1 / [(n+n1)×R]。 Assuming the fixed coil covers half of the adjustable coil and does not cover the original coil, the effective number of turns of the variable coil is 150 turns and 300 turns respectively. When the fixed coil covers half of the adjustable coil, the number of turns of the fixed coil wound on the outside of the adjustable coil is 432-150=282 turns.

Claims

1. An adjustable high-current generator based on an autotransformer, comprising an autotransformer body (1), an annular iron core (2) on the autotransformer body (1), a plurality of adjustable coils (3) wound on the annular iron core (2), a voltage adjustment knob (4) rotatably mounted on the autotransformer body (1), and a sliding contact (5) on the voltage adjustment knob (4) that slides in contact with each adjustable coil (3), characterized in that: A number of turns of fixed coil (6) are wound on the toroidal iron core (2) and do not contact the sliding contact (5). One end of the fixed coil (6) is connected to one end of the adjustable coil (3) according to the polarity. The other end of the fixed coil (6) and the coil between the sliding contact (5) form the primary coil. A low-voltage high-current secondary coil (7) is wound on the toroidal iron core (2).

2. The adjustable high-current generator based on an autotransformer as described in claim 1, characterized in that... The adjustable coil (3) is wound in a single layer around the outside of the entire toroidal core (2). The fixed coil (6) is located outside one end of the adjustable coil (3) and wound around the outside of the adjustable coil (3) and the toroidal core (2). An insulating layer (8) is provided between the fixed coil (6) and the adjustable coil (3) for mutual insulation and isolation. The low-voltage high-current secondary coil (7) is located at the position of the fixed coil (6) and wound around the outside of the fixed coil (6), the adjustable coil (3) and the toroidal core (2).

3. The adjustable high-current generator based on an autotransformer as described in claim 2, characterized in that... The low-voltage high-current secondary coil (7) is a thick wire wound around the outside of the fixed coil (6), and the outside of the low-voltage high-current secondary coil (7) is wrapped with an insulating jacket (71) that is insulated and isolated from the fixed coil (6).

4. The adjustable high-current generator based on an autotransformer as described in claim 1, characterized in that... The adjustable coil (3) is wound in a single layer around most of the surface of the toroidal core (2), and the fixed coil (6) is wound in multiple layers around the other small parts of the surface of the toroidal core (2) outside the adjustable coil (3). The low-voltage, high-current secondary coil (7) is located at the position of the fixed coil (6) and wound around the outside of the fixed coil (6) and the toroidal core (2).

5. An adjustable high-current generator based on an autotransformer as described in claim 4, characterized in that... The low-voltage high-current secondary coil (7) is a thick wire wound around the outside of the fixed coil (6), and the outside of the low-voltage high-current secondary coil (7) is wrapped with an insulating jacket (71) that is insulated and isolated from the fixed coil (6).

6. The adjustable high-current generator based on an autotransformer as described in claim 4, characterized in that... The autotransformer body (1) is provided with a first terminal (11) and a second terminal (12) that are connected to the two ends of the fixed coil (6) by wires respectively. One end of the adjustable coil (3) is connected to the first terminal (11) by wire according to polarity. The autotransformer body (1) is provided with a third terminal (13) that is connected to the sliding contact (5) by wire. The third terminal (13) and the second terminal (12) constitute the primary side terminal.

7. An adjustable high-current generator based on an autotransformer as described in claim 4, characterized in that... The autotransformer body (1) is provided with two output terminals (14, 15) that are respectively connected to the two ends of the low-voltage high-current secondary coil (7), forming the secondary terminal.

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