A method for determining the radial magnetic gap of an exciter and a method for calculating the magnetic center difference.

Abstract

This invention discloses a method for determining the radial magnetic gap of an exciter and a method for calculating the magnetic center difference. The method for determining the radial magnetic gap includes the following steps: dividing the upper surfaces of the rotor and stator into four equal parts at 90° intervals; determining the first set of radial magnetic gap distance values; rotating the rotor 180 degrees; measuring the distance between corresponding marks on the horizontal and vertical axes after rotation to obtain the second set of radial magnetic gap distance values; and adjusting the radial magnetic gap if the horizontal or vertical gap adjustment value is greater than or equal to the average gap value X%. The method for calculating the magnetic center difference of the exciter's magnetic force is based on the difference *a* between the sum of the elongations *D* of the motor and blower shafts and the magnetic center offset of the exciter. This method solves the current problem of lacking relevant maintenance techniques for the magnetic gap and magnetic center difference of exciters.

Description

Technical Field

[0001] This invention belongs to the field of energy and thermodynamics, and relates to a method for determining the radial magnetic gap of an exciter and a method for calculating the magnetic center difference. Background Technology

[0002] The Power Generation Branch of Ansteel Energy and Power Plant currently has eight electric blowers, primarily responsible for supplying air to the blast furnace for ironmaking. Their main working principle involves an exciter controlling the speed of a variable frequency motor, which in turn drives an axial compressor to generate a certain pressure of air to supply air to the blast furnace. Therefore, the electric blower is one of the key pieces of equipment in the Energy and Power Plant and a crucial link in ensuring stable blast furnace production. In April 2020, during the commissioning phase after installation, the exciter of the No. 8 electric blower experienced increased current and voltage, and the exciter coil overheated to 90°C, triggering an alarm and preventing the blower from being put into operation. Summary of the Invention

[0003] To address the exciter overheating problem, the present invention employs a method for determining the radial magnetic gap of an exciter, comprising the following steps:

[0004] Divide the end faces of both sides of the rotor and stator into four equal parts at 90°. The outer edges of the rotor and stator are marked accordingly according to the division. The radial magnetic gap between corresponding marks is measured to obtain the first set of exciter radial magnetic gap distance values ​​X. 1、 X 2、 Y 1、 Y2; Rotate the rotor 180 degrees in the direction of rotation during operation; After rotating the magnetizer, the distance between the corresponding marks on the horizontal and vertical axes was measured again to obtain the second set of exciter radial gap distance values ​​X. 11、 X 22、 Y 11、 Y 22 ; The horizontal clearance adjustment value for the radial magnetic gap of the exciter is determined as follows: ; The vertical clearance adjustment value for the radial magnetic gap of the exciter is: ; The average gap value Z is: ; If the horizontal or vertical clearance adjustment value is greater than or equal to the average clearance value X%, then the radial magnetic gap of the exciter needs to be adjusted.

[0005] Furthermore: the range of X% is 5%–10%.

[0006] According to any one of the methods for determining the radial magnetic gap of an exciter, the radial magnetic gap of the exciter is adjusted by moving the position of the stator horizontally or the height of the platform below the stator.

[0007] A method for calculating the magnetic mean difference of an exciter's magnetic force includes the following steps: Obtain the elongation ΔL of the variable frequency motor rotor in the working state, and the elongation B of the blower rotor at the coupling in the working state; in the non-working state, the distance a1 between the coupling end, the stator coil and the rotor end face; in the non-working state, the distance a2 between the exciter tail end, the stator and the rotor end face. The sum of the elongations D of the motor and blower shafts is calculated based on the elongation ΔL of the variable frequency motor rotor under working conditions and the elongation B of the blower rotor at the coupling under working conditions. Based on the non-working state, the distance a1 between the coupling end, stator coil and rotor end face; and the distance a2 between the exciter tail end, stator and rotor end face, calculate the magnetic center offset a of the exciter. The magnetic center deviation of the exciter's magnetic force is obtained by using the sum of the elongations D of the motor and blower shafts and the difference a between the magnetic center deviation of the exciter and the magnetic center deviation of the exciter.

[0008] Furthermore, the expression for the sum of the elongations D of the shafts of the electric motor and the blower is as follows: D = △L / 2 + B Furthermore, the expression for the magnetic center offset 'a' of the exciter is as follows.

[0009]

[0010] Furthermore: Once the radial magnetic gap of the exciter is determined, the position of the stator is adjusted axially according to the magnetic mean difference, in the opposite direction to the extension direction of the motor and blower shafts.

[0011] This invention provides a method for judging the radial magnetic gap of an exciter and a method for calculating the magnetic center difference. Through analysis and research on the unique fault of overheating in electric blower exciters, combined with practical experience and existing technology, a set of methods for measuring and adjusting magnetic center and magnetic separation has been summarized. This solves the problem that there is currently no related maintenance technology for the magnetic gap and magnetic center of exciters. It explores a new approach in maintenance, fills the maintenance gap in the correlation between electrical and mechanical aspects in actual maintenance work, provides a certain theoretical basis for the adjustment of magnetic center and magnetic gap, and verifies the feasibility of the maintenance technology method through experimental results.

[0012] Based on the method of this application, it can be extended to related equipment, such as various large electric motors, exciters, and generators. This method can be used for measurement and adjustment to ensure installation accuracy, ensure good equipment operation, extend equipment service life, and create certain economic value.

[0013] The method described in this application fills a gap in the maintenance of exciters and also serves as a reference for the future maintenance of other types of large electric motors, generators, and exciters in terms of magnetic field and magnetic gap. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a simplified structural diagram of the AV80-15 axial compressor; Figure 2 This is a schematic diagram of the end face when the radial magnetic gap is not rotated during adjustment; Figure 3 This is a schematic diagram of the rotating rear end face during radial magnetic gap adjustment; Figure 4 This is a schematic diagram illustrating the measurement of the offset of the magnetic centerline of a magneto. Figure 5 Extract the exciter rotor coil gripper. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Figure 1 This is a simplified structural diagram of the AV80-15 axial flow compressor; where #1, #2, #3, and #4 are support bearings. Figure 2 This is a schematic diagram of the end face when the radial magnetic gap is not rotated during adjustment; Figure 3 This is a schematic diagram of the rotating rear end face during radial magnetic gap adjustment; A method for determining the radial magnetic backlash of an exciter includes the following steps: S11: Divide the end faces of each side of the rotor and stator into four equal parts at 90° angles. S12: Mark the corresponding sections on the outer edges of the rotor and stator according to the division; S13: Measure the distance between the corresponding marks to obtain the first set of exciter radial magnetic gap distance values ​​X. 1、 X 2、 Y 1、 Y2; S14: Rotate the rotor 180 degrees in the direction of rotation during operation; S15: Measure the distance between the corresponding marks on the horizontal and vertical axes after rotation again to obtain the second set of exciter radial gap distance values ​​X. 11、 X 22、 Y 11、 Y 22 ; S16: The horizontal clearance adjustment value for the radial magnetic gap of the exciter is determined as follows: ; The vertical clearance adjustment value for the radial magnetic gap of the exciter is: ; The average gap value Z is: ; If the horizontal or vertical clearance adjustment value is greater than or equal to the average clearance value X%, then the radial magnetic gap of the exciter needs to be adjusted.

[0019] Steps S11, S12, S13, S14, S15, and S16 are executed sequentially. The radial magnetic gap of the exciter can be measured using a long wedge gauge; Furthermore, the range of X% is 5%–10%.

[0020] According to any one of the methods for determining the radial magnetic gap of an exciter, the adjustment is made by moving the position of the stator horizontally or the height of the platform below the stator.

[0021] When other conditions change, i.e. before the exciter is installed, the radial clearance can also be adjusted by changing the relevant position of the rotor; To ensure the electrical performance of the exciter, the magnetic center of the exciter's stator and rotor must be aligned during operation, that is, the center CC of the stator coil must coincide with the center C'C' of the rotor. Since our unit currently lacks the technical requirements and methods for overhauling the exciter's magnetic field, we can only rely on our overhaul experience. Considering the impact of the thermal expansion of the blower rotor on the axial position of the variable frequency motor rotor (the variable frequency motor and the exciter rotor are coaxial) under actual operating conditions, as well as the thermal expansion of the variable frequency motor rotor itself, we must ensure that the static center CC of the exciter is offset from the rotor center C'C' by a certain value. Figure 4 This is a schematic diagram illustrating the measurement of the offset of the magnetic centerline of a magneto. A method for calculating the magnetic mean difference of an exciter's magnetic force includes the following steps: S21: Obtain the elongation ΔL of the variable frequency motor rotor in the working state, the elongation B of the blower in the working state; the distance a1 between the exciter coupling end, the stator coil and the rotor end face in the non-working state; the distance a2 between the exciter tail end, the two ends of the stator and the rotor sleeve in the non-working state. S22: Based on the elongation ΔL (mm) of the variable frequency motor rotor in working condition and the elongation B (mm) of the blower rotor at the coupling in working condition, this value is calculated by the manufacturer to obtain the sum of the elongation D (mm) of the motor and blower shafts. D = △L / 2 + B; The elongation of the rotor of a variable frequency motor can be calculated as 1 mm per meter of length between the center lines of the two journals; S23: In the non-working state, calculate the magnetic center offset a of the exciter based on the distance a1 between the coupling end, the stator and rotor end faces, and the distance a2 between the two ends of the stator at the tail end of the exciter and the rotor sleeve; The magnetic center offset value can be measured during installation using a steel ruler or similar tool. The expression for the magnetic center offset 'a' of the exciter is as follows:

[0022] S24: Based on the sum of the elongations D of the motor and blower shafts and the difference a of the magnetic center offset of the exciter, the magnetic center offset of the exciter is obtained. Magnetic mean difference = Da = ΔL / 2 + B

[0023] Steps S21 / S22 / S23 / S24 are executed sequentially; When the exciter is connected to the generator (motor) by a coupling or when the two rotors are coaxial, the generator has a certain elongation after heating due to its large size, denoted by ΔL. Furthermore, after the generator is connected to the blower by a coupling, there is another change in the elongation of the shaft due to heating, denoted by B. The two combined (ΔL + B) exert an axial force on the exciter rotor. If the exciter is in the magnetic neutral position after cold adjustment, after normal operation, the heated shafts of the blower and generator will elongate, causing a change in the axial position of the exciter shaft. In other words, the magnetic neutral position changes after normal operation, affecting the normal operation of the exciter. Therefore, it is necessary to calculate the magnetic neutral difference in advance, adjust the magnetic neutral position, and reserve sufficient allowance for the normal operation of the exciter to ensure that the exciter's CC and C'C' coincide. After measuring and adjusting the magnetic center and gap of the exciter, and determining its position, new holes were drilled and reamed on both sides of the exciter stator, and φ8 tapered pins were installed for positioning to facilitate future maintenance and construction. The unit was retested, and the exciter temperature remained at around 55℃, indicating smooth operation and ensuring the blast furnace air supply requirements were met. A method for adjusting the measurement and calculation of the magnetic center offset value of an exciter, wherein after the radial magnetic gap of the exciter is determined, the position of the stator is adjusted in the horizontal or vertical radial direction according to the measured results.

[0024] Axial adjustment, also known as determining the magnetic center position, is used to determine the axial position of the exciter when it is connected to other equipment. The position of the stator is adjusted axially according to the magnetic center difference, in the opposite direction to the extension direction of the motor and blower shafts. This prevents magnetic center deviation from causing the exciter to overheat and burn out or reducing its service life.

[0025] The prerequisite for adjusting the exciter stator is that the turbine (blower, steam turbine) and the generator (motor) and the exciter center (coaxiality) meet the specifications and the coupling is installed well. Adjusting the stator is relatively difficult, so adjusting the stator is more convenient and efficient. Before the overall equipment is installed, the exciter rotor position (moving the motor position) and the exciter stator position can be adjusted in combination according to the actual situation. The exciter and the rotor of the variable frequency motor in this unit are coaxial, and some are connected by a coupling; Example 1: Analysis of heat generation before disassembly of the electric fan: including: 1) whether the temperature sensing element has failed; 2) Check for scraping or collision between the stator and rotor, and ensure the clearance is appropriate; 3) Are there any malfunctioning control components in the PLC cabinet? 4) Check for any damage or detachment of the stator magnets, coils, and rotor coils; 5) Has the position in the magnet changed? Problems were discovered after disassembly: 1) Two control switches on the PLC cabinet are not functioning properly; 2) The rotor coil heats up and changes color; 3) The horizontal gap between the stator and rotor is 0.60mm on one side and 3-2mm on the other side. The magnetic field changes and the current becomes unstable.

[0026] Processing procedure: 1) Replace the two faulty control switches inside the PLC cabinet; 2) Disassembly and inspection of the exciter rotor components; 3) Measurement and adjustment of the radial magnetic gap of the exciter; 4) Measurement and adjustment of the exciter's magnetic center offset; The exciter rotor coil and other auxiliary components are mounted on the tapered shaft at the tail of the motor. Due to corrosion and excessive tightening, the coil and auxiliary components are easily damaged by methods such as twisting and knocking. To avoid secondary damage, a special tool is made according to the rotor structure characteristics to disassemble the rotor electrical components.

[0027] Figure 5 It is a gripper for extracting the exciter rotor coil. A gripper for extracting exciter rotor coils includes: a pressure plate flange; the pressure plate flange is made of iron. The rotor coil flange is divided into six equal parts on the same circumference, and six M12 screw holes are determined. After measurement, six double-ended screws of appropriate length and a steel plate with appropriate outer diameter hole spacing and thickness are manufactured, along with a 6-ton screw jack. The exciter rotor coil and other components are disassembled by gradually increasing pressure using a top-pressure method. After disassembly, the exciter rotor undergoes professional testing and processing to ensure it meets usage requirements. The manufacture of specialized top-pressure tools improves maintenance efficiency and ensures the integrity of all components on the rotor.

[0028] The exciter's rotor is coaxial with the variable frequency motor. The exciter's rotor coil and other electrical components are fixed on the shaft using the motor's tail end. The stator is fixed on the exciter's base. This ensures that the radial magnetic gap and axial magnetic gap between the stator and rotor meet the standards, guaranteeing stable operation of the exciter. This, in turn, maintains stable motor terminal voltage and improves the static stability of the motor. In the event of a fault inside the variable frequency motor, the exciter is demagnetized to reduce the degree of damage from the fault. A method for determining the radial magnetic gap adjustment of an exciter includes the following steps: S11: Divide the upper surfaces of the rotor and stator into four equal parts at 90° angles; S12: Mark the corresponding sections on the outer edges of the rotor and stator according to the division; S13: Measure the distance between the corresponding marks to obtain the first set of exciter radial magnetic gap distance values: X1=0.6mm, X2=3.2mm, Y1=1.95mm, Y2=1.85mm; S14: Rotate the rotor 180 degrees in the direction of rotation during operation; S15: Measure the distance between the corresponding marks on the horizontal and vertical axes after rotation again to obtain the second set of exciter radial gap distance values ​​X. 11 =0.6mm, X 22 =3.2mm, Y 11 =1.95mm, Y 22 =1.85mm; The horizontal clearance adjustment value for the radial magnetic gap of the exciter is determined as follows:

[0029] With X1=0.6mm, X2=3.2mm, X 11 =0.6mm, X 22 Substituting 3.2mm into the formula, we get the horizontal clearance adjustment value: -1.3mm, which means adjusting it to the right by 1.3mm. The vertical clearance adjustment value for the radial magnetic gap of the exciter is: ;Y1=1.95mm, Y2=1.85mm; Y 11 =1.95mm, Y 22 Substituting 1.85mm into the formula, we get a vertical adjustment value of 0.05mm; The average gap value Z is: Substituting X1=0.6mm, X2=3.2mm, Y1=1.95mm, and Y2=1.85mm into the formula, we get Z=1.9mm; The average gap value X% = 0.095 - 0.19 mm; If the vertical adjustment value is 0.05mm < the average gap value X%, then no adjustment is needed in the radial and vertical directions of the exciter. Horizontal clearance adjustment value: If 1.3mm > average clearance value X%, then the exciter's radial and horizontal direction needs adjustment; A method for calculating the magnetic mean difference of an exciter's magnetic force includes the following steps: S21: Obtain the elongation ΔL of the variable frequency motor rotor under operating conditions: 3.5 meters, shaft length 3.5 meters. 1mm = 3.5mm; The elongation B of the blower during operation is 0.5 mm. In the non-operating state, the distance 'a' between the exciter coupling end, the stator coil, and the rotor end face. 1=178mm; The distance a between the exciter tail end, both ends of the stator, and the rotor sleeve in the non-working state. 2= 182mm; S22: Based on the elongation ΔL (mm) of the variable frequency motor rotor in working condition and the elongation B (mm) of the blower rotor at the coupling in working condition, this value is calculated by the manufacturer to obtain the sum of the elongation D (mm) of the motor and blower shafts. D = △L / 2 + B; Calculate D as 2.25 mm; The elongation of the rotor of the variable frequency motor can be calculated as 1 mm per meter of length between the center lines of the two journals; S23: In the non-working state, based on the distance a1 between the two ends of the stator and the rotor sleeve at the coupling end and the distance a2 between the two ends of the stator and the rotor sleeve at the exciter tail end; calculate the magnetic center offset a of the exciter. The magnetic center offset value can be measured during installation using a steel ruler or similar tool. The expression for the magnetic center offset 'a' of the exciter is as follows:

[0030] a = 182 - 178 / 2 = 2mm S24: Based on the difference 'a' between the sum of the elongations D of the motor and blower shafts and the magnetic center offset of the exciter, the magnetic center deviation of the exciter's magnetic force is obtained as follows: Magnetic center deviation = Da = 2.25 - 2 = 0.25mm When the calculation result is positive, the stator moves towards the tail end; when the result is negative, the stator moves towards the coupling end. Therefore, in the static state of the exciter, the stator axis should be adjusted 0.25mm towards the tail end of a2 so that the exciter stator and rotor will coincide during normal operation. After measuring and adjusting the magnetic center and gap of the exciter, and determining its position, new holes were drilled and reamed on both sides of the exciter, and φ8 tapered pins were installed for positioning to facilitate future maintenance and construction. The exciter was retested, and the temperature remained at approximately 55℃. The unit operated smoothly, ensuring the blast furnace air supply requirements were met. This method can be applied to the measurement and adjustment of magnetic gap and magnetic field in exciters, generators, and motors. The solution can be optimized and selected according to the actual situation of the equipment.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the magnetic mean difference of an exciter's magnetic force, characterized in that: Includes the following steps: Obtain the elongation ΔL of the variable frequency motor rotor in the working state, and the elongation B of the blower rotor at the coupling in the working state; in the non-working state, the distance a1 between the coupling end, the stator coil and the rotor end face; in the non-working state, the distance a2 between the exciter tail end, the stator and the rotor end face. The sum of the elongations D of the motor and blower shafts is calculated based on the elongation ΔL of the variable frequency motor rotor under working conditions and the elongation B of the blower rotor at the coupling under working conditions. Based on the non-working state, the distance a1 between the coupling end, stator coil and rotor end face; and the distance a2 between the exciter tail end, stator and rotor end face, calculate the magnetic center offset a of the exciter. The magnetic center deviation of the exciter's magnetic force is obtained by the difference a between the sum of the elongations D of the shafts of the motor and the blower and the magnetic center offset of the exciter. The expression for the sum of the elongations D of the shafts of the electric motor and the blower is as follows: D = △L / 2 + B.

2. The method for calculating the magnetic mean difference of exciter magnetic force according to claim 1, characterized in that: The expression for the magnetic center offset 'a' of the exciter is as follows: 。 3. The method for calculating the magnetic mean difference of the exciter's magnetic force according to any one of claims 1-2, characterized in that: Once the radial magnetic gap of the exciter is determined, the position of the stator is adjusted axially according to the magnetic mean difference, in the opposite direction to the extension direction of the motor and blower shafts.

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