Method of regulating a discharge coil

Abstract

The application provides a discharge coil adjusting method, the discharge coil comprises a left core (101), a right core (102), the left core (101) and the right core (102) are abutted and are lower air gap (103) and upper air gap (104), further comprising coil (105), the left core (101), the right core (102), lower air gap (103) and upper air gap (104) form a complete core, and the coil (105) is sleeved on the top and forms a complete discharge coil body;The left core (101) and the right core (102) are made of the processed silicon steel sheet strip, are formed into annular cores on the mould, become annular cores, are cut into a pair of C-shaped cores after vacuum impregnation and curing forming;Air gap pad is made of insulating material.The discharge coil manufactured by the application has good excitation characteristics and discharge characteristics.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of discharge coil, in particular to a discharge coil adjusting method. BACKGROUND

[0002] Discharge coil is used in reactive power compensation device in power system, and is connected in parallel with high-voltage shunt capacitor bank, so that the residual charge of the capacitor can be quickly discharged after the capacitor is cut off from the power system, and the residual voltage of the capacitor reaches the required value within a specified time.

[0003] Because of the requirement of discharge time (5s) in the standard, the discharge coil cannot be designed to be as small as possible in product loss like voltage transformer.

[0004] According to the latest anti-measures requirements of State Grid, the requirement of 1.9 times excitation characteristic must also be met, and the core loss should not be too large.

[0005] In the old technology, there are ways of using laminated core and ring core, but the problem is that the laminated core loss is too large and it is difficult to meet the excitation characteristic requirement, and the ring core is difficult to meet the discharge time requirement. Both of these two ways need to solve the technical problem by using extremely high design margin and greatly increasing the cost. SUMMARY

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present application is to provide a discharge coil adjusting method which adjusts the air gap of the coil to meet the discharge time requirement on the basis of changing the old structure of the core. The present application provides a discharge coil and an adjusting method thereof.

[0007] A discharge coil comprises a left core and a right core, the left core and the right core are connected at the lower air gap and the upper air gap, and further comprises a coil, the left core, the right core, the lower air gap and the upper air gap form a complete core, and the coil is sleeved on the complete core to form a complete discharge coil body; the left core and the right core are long strips of processed silicon steel sheets, which are formed into ring cores on a mold, and are cut into a pair of C-shaped cores after vacuum impregnation and curing; the air gap pad is made of insulating material.

[0008] As a further improvement of the present application, the ring core is cut at the center position or at any position on the cutting surface when cutting, and the cutting surface is required to be smooth and complete.

[0009] As a further improvement of the present application, the thickness of the air gap is 0mm.

[0010] An adjusting method of the discharge coil according to any one of the above-mentioned discharge coils, comprising the following steps:

[0011] Step 1: derive the theoretical inductance by the discharge time formula; the general calculation formula of the discharge time in engineering application is

[0012]

[0013] Wherein, t is the discharge time, L1 is the inductance, R1 is the DC resistance of the inductive coil, U1 is the rated terminal voltage of the capacitor;

[0014] Step 2: assemble the product, prepare for the initial adjustment, preset an air gap thickness value in the initial adjustment stage;

[0015] Step 3: adjust the inductance of the high-voltage coil through the air gap to meet the requirement of the discharge time: apply the rated voltage to the primary high-voltage coil through the booster, and measure the primary no-load current value;

[0016] Step 4: calculate the reactance value through the volt-ampere method, reactance = applied voltage / no-load current, convert into inductance, inductance = reactance / 2πf, when there is an error in the theoretical inductance, adjust the air gap thickness, the size of the air gap thickness is adjusted according to the derived theoretical inductance and test verification;

[0017] Step 5: compare with the theoretical inductance, select the optimal result of the air gap thickness, at this time, the value of the air gap thickness is the total thickness, and the upper and lower air gaps are each half of the total thickness.

[0018] As a further improvement of the application, the size of the air gap thickness is 0-2mm.

[0019] As a further improvement of the application, in step 1, when the discharge time t is 5 seconds, the value of t is 5 seconds during calculation, the calculated value of the inductance L1 of the coil is obtained, and the inductance L1 of the coil should be less than the calculated value.

[0020] The beneficial effects of the application are:

[0021] 1. The structure is easy to manufacture and suitable for large-scale production. 2. Transition from the old technology to the application does not require large-scale equipment modification, and the modification cost is low. 3. The discharge coil manufactured by the application has good excitation characteristics and discharge characteristics, which can meet the latest national power grid material procurement standards. 4. The discharge coil manufactured by the application has high cost performance and good economy. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic diagram of a discharge coil structure of the application;

[0023] Figure 2 is an exploded view of a discharge coil of the application;

[0024] Figure 3is a test circuit diagram of the present application.

[0025] The names of the components in the figure are as follows:

[0026] Left core 101, right core 102, lower air gap 103, upper air gap 104, coil 105.

[0027] Booster 1, voltmeter 2, ammeter 3, test object 4 (discharge coil). DETAILED DESCRIPTION

[0028] The present application will be further described below in conjunction with the drawings.

[0029] 1. The core is a long strip of processed silicon steel sheet, which is formed into a ring-shaped core on a special mold, and after vacuum impregnation and curing, it is cut into a pair of C-shaped cores. The left and right cores are cut from the ring-shaped core, and in addition to the center position as shown, they can be cut at any position on the cutting surface, as long as the cutting surface is smooth and the butt joint is complete.

[0030] 2. A suitable air gap pad is provided at the butt joint of the C-shaped core to form the magnetic circuit reluctance. The air gap pad is made of insulating materials, such as but not limited to epoxy laminated board and film.

[0031] 3. The coil, core and air gap pad are assembled completely. As shown in Figure 1 , a discharge coil core structure, as shown in Figure 2 , includes left core 101, right core 102, lower air gap 103, upper air gap 104, which constitutes a complete core, and the coil 105 is sleeved on it to form a complete product body. The core is cut from a complete ring-shaped core into left core 101 and right core 102, and the butt joint of the two is lower air gap 103 and upper air gap 104.

[0032] 4. The theoretical inductance is derived from the discharge time formula.

[0033] The general calculation formula for discharge time in engineering application is

[0034]

[0035] Where t: discharge time L1: inductance R1: DC resistance of inductive coil U1: rated voltage of capacitor.

[0036] 5. As shown in Figure 3 , the rated voltage is applied to the primary high-voltage coil through the booster, and the primary no-load current value is measured. The inductance is calculated by the voltammetry method, and when there is an error in the calculation, the air gap thickness is adjusted. The adjustment of the air gap size is based on the design calculation results and test verification, and generally in the range of 0-2mm, and if necessary, it can be added.

[0037] Through the test verification, the parameters calculated according to the formula (1) can meet the discharge time requirements of the product required by the national standard.

[0038] The main purpose of the discharge coil is to discharge the high-voltage parallel capacitor, and the standard has a clear provision for the discharge time, and the discharge process is completed by the coil 105 oscillation consuming electric charge. To meet the requirement that the coil 105 releases the capacitor stored charge to below the safe voltage within the specified time of 5 seconds, it is necessary to adjust the inductance of the high-voltage coil through the air gap to meet the discharge time requirement. For the discharge coil, the product structure is different for different voltage levels, and the no-load current required by the product is different, so the core is adopted, and the size of the upper and lower air gaps is adjusted for different no-load currents. The feature of this core is that the size of the air gap can be adjusted at will, and the air gap can be completely removed, that is, the air gap can be zero, which meets the needs of different products.

[0039] For example:

[0040] A certain type of discharge coil, voltage level is 35KV, rated terminal voltage After the coil is wound, the measured DC resistance R1 is 9875Ω.

[0041] First step: according to the known conditions, calculate the inductance that meets the standard requirements

[0042] According to the discharge calculation formula

[0043]

[0044] It can be deduced that when the discharge time t is less than 5 seconds, the inductance L1 of the coil should be less than 3783H.

[0045] Second step: assemble the product and prepare for initial adjustment. In the initial adjustment stage, a air gap is preset, and in this example, the initial adjustment air gap is preset to 0.3mm.

[0046] Third step: test, apply voltage to the coil through the booster, and record the test current. The applied voltage can be the rated terminal voltage U1, or other values. In this embodiment, the rated terminal voltage U1 is used.

[0047] Fourth step: calculate the reactance value by volt-ampere method, reactance = applied voltage / no-load current, convert to inductance value, inductance = reactance / 2πf, compare with the designed inductance, and select the optimal result. The results are as follows:

[0048] Air gap thickness mm 0.3 0.6 1.1 1.6 Applied voltage V 24249 24249 24249 24249 No-load current mA 5 11 17 22 Reactive impedance Ω 4849800.00 2204454.55 1426411.76 1102227.27 Inductance H 15437.39 7017.00 4540.41 3508.50

[0049] From the measured results, it can be seen that the total thickness of the air gap of 1.6mm meets the design requirements, and the air gap thickness of this type is confirmed to be 0.8mm for the upper and lower air gaps.

[0050] The improved method has been proved by practice that the product can meet the discharge time of the discharge coil and ensure the excitation characteristic requirement of the product. Compared with the existing technology of the laminated core or the ring core, the product has excellent cost performance.

[0051] The above is the further detailed description of the present application combined with the specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field of the present application, some simple deductions or replacements can be made without departing from the concept of the present application, and all of them shall be regarded as the protection scope of the present application.

Claims

1. A method for adjusting a discharge coil, the discharge coil comprising a left iron core (101) and a right iron core (102), wherein the joint between the left iron core (101) and the right iron core (102) is a lower air gap (103) and an upper air gap (104), and the joint between the left iron core (101) and the right iron core (102) has only the lower air gap (103) and the upper air gap (104), and further comprising a coil (105), wherein the left iron core (101), the right iron core (102), the lower air gap (103) and the upper air gap (104) form a complete iron core, and the coil (105) is fitted on top of it to form a complete discharge coil body; the left iron core (101) and the right iron core (102) are formed by winding a pre-processed silicon steel strip around a mold to form an annular iron core, and after vacuum impregnation and curing, they are cut into a pair of C-shaped iron cores; the air gap pads are made of insulating material, characterized in that: Includes the following steps: Step 1: Derive the theoretical inductance using the discharge time formula; the general formula for calculating discharge time in engineering applications is as follows: Where t is the discharge time, L1 is the inductance, R1 is the DC resistance of the inductor coil, and U1 is the rated terminal voltage of the capacitor. Step 2: Assemble the product and prepare for initial adjustment. In the initial adjustment stage, preset an air gap thickness value. Step 3: Adjust the inductance of the high-voltage coil through the air gap to meet the discharge time requirements: Apply the rated voltage to the primary high-voltage coil through the boost converter and measure the primary no-load current value; Step 4: Calculate the reactance value using the volt-ampere method. Reactance = applied voltage / no-load current. Convert this to the inductance value. Inductance = reactance / 2πf. When there is an error between the inductance value and the theoretical inductance value, adjust the air gap thickness. The size of the air gap thickness is adjusted based on the derived theoretical inductance value and experimental verification. Step 5: Compare with the theoretical inductance to select the optimal air gap thickness. At this point, the air gap thickness is equal to the total thickness, with the upper and lower air gaps each being half of the total thickness.

2. The method for adjusting a discharge coil according to claim 1, characterized in that: The thickness of the air gap is 0-2 mm.

3. The method for adjusting a discharge coil according to claim 1, characterized in that: In step 1, when the discharge time t is 5 seconds, the calculation is performed with t set to 5 seconds to obtain the calculated value of the coil inductance L1. The coil inductance L1 should be less than this calculated value.

4. The method for adjusting a discharge coil according to claim 1, characterized in that: When cutting the annular iron core, the cut can be made at the center or at any point on the cutting surface. The cutting surface must be smooth and flat, and the joints must be complete.

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