Tool for eliminating shaft current of three-phase asynchronous motor

Abstract

A three-phase asynchronous motor shaft current elimination tool comprises an adjustable support (1), a carbon brush assembly (2) and a grounding assembly (3), the adjustable support (1) is installed on a motor output end shell, the carbon brush assembly (2) is installed on the adjustable support (1), the carbon brush assembly (2) is electrically connected with the adjustable support (1), one end of the grounding assembly (3) is electrically connected with the adjustable support (1), and the other end of the grounding assembly (3) is grounded; the utility model has the advantages that: 1, the safety is improved, the motor bearing is effectively prevented from being damaged by shaft current, and potential safety accidents are avoided; the service life is prolonged, bearing abrasion caused by shaft current is reduced, and the overall service life of the motor is prolonged;

Description

Technical Field

[0001] The utility model relates to the field of motor equipment, in particular to a tool for eliminating shaft current of a three-phase asynchronous motor. Background Art

[0002] Currently, three-phase asynchronous motors are essential power equipment in modern industrial production, and their operational stability and efficiency directly impact the entire production system. However, during long-term operation, shaft current issues can become increasingly prominent, posing a serious threat to the motor and its associated equipment. During rotation, the shaft of a three-phase asynchronous motor can generate static charge due to friction, oil film rupture, and other factors. Furthermore, rotor imbalance can cause the axis of rotation to deviate, generating shaft currents. These factors include high-order harmonic components in the power supply voltage during inverter operation, the strong electric field from high-voltage equipment at the site of three-phase asynchronous motor operation, the accumulation of static charge, and improper connection of external power cables. These factors can cause the shaft's potential to change, creating a potential difference between the shaft and the bearings, base, or housing. If this potential difference is large enough, it can break down insulating media such as the bearing oil film, generating shaft currents. Furthermore, three-phase asynchronous motors generate an alternating magnetic field during operation. When the geometric dimensions and mounting positions of the stator, rotor, and other metal components of a three-phase asynchronous motor are improperly designed, an alternating electromagnetic field is easily generated on the rotating shaft. This alternating electromagnetic field induces eddy currents in the metal components, leading to shaft currents. When the circumferential magnetic resistance of the stator core of a three-phase asynchronous motor is unbalanced, an alternating magnetic flux is generated that intersects the shaft, inducing a shaft voltage at both ends of the shaft. This shaft voltage is generated axially and, if it forms a closed loop with bearings or other conductive components on either side of the shaft, generates shaft currents. When shaft currents pass through the bearings, they generate high temperatures on the inner surfaces of the bearings, causing localized melting, resulting in small pits or arc scars. This damage accelerates bearing wear, reduces bearing service life, and may even lead to bearing failure. Long-term shaft currents can also cause the bearing alloy to gradually adhere to the shaft journal, destroying the bearing shell's working surface, causing bearing overheating, and even melting the bearing alloy.

[0003] The presence of shaft current can not only damage bearings and shorten the life of the motor, but can also cause safety accidents. In the prior art, although there are many methods to try to solve the shaft current problem, most of them have problems such as complex structure, high cost or poor effect. Utility Model Content

[0004] The purpose of this utility model is to provide a tool for eliminating the shaft current of a three-phase asynchronous motor in view of the above-mentioned shortcomings.

[0005] The utility model includes an adjustable bracket, a carbon brush assembly and a grounding assembly.

[0006] The adjustable bracket is installed on the motor output end housing, the carbon brush assembly is installed on the adjustable bracket, the carbon brush assembly is electrically connected to the adjustable bracket, one end of the grounding assembly is electrically connected to the adjustable bracket, and the other end of the grounding assembly is grounded.

[0007] The adjustable bracket consists of an A arm, a B arm and a C arm. One end of the A arm is mounted on the motor output end housing by bolts, one end of the B arm is mounted on the middle of the A arm by bolts, the other end of the B arm is mounted on the motor output end housing by bolts, and one end of the C arm is mounted on the other end of the A arm by bolts.

[0008] The carbon brush assembly is installed on the C-arm, and one end of the grounding assembly is installed on the A-arm.

[0009] The carbon brush assembly includes a graphite carbon brush, a carbon brush box and a compression retaining spring. The graphite carbon brush is movably installed in the carbon brush box. When one end of the graphite carbon brush contacts the outer wall of the motor power output shaft, the compression retaining spring presses on the other end of the graphite carbon brush, making the graphite carbon brush close to the outer wall of the motor power output shaft.

[0010] A carbon brush mounting groove is provided in the middle of the carbon brush box. The graphite carbon brush is located in the carbon brush mounting groove and can slide back and forth along the carbon brush mounting groove. The graphite carbon brush is electrically connected to the A-arm through a wire.

[0011] A retaining spring insertion slot is provided at the bottom of the carbon brush box. The compression retaining spring includes a V-shaped spring and a coil spring. The coil spring is installed on the top of the V-shaped spring through rivets. The V-shaped spring is inserted into the retaining spring insertion slot. The coil spring is pressed against the end of the graphite carbon brush, and the coil spring continuously provides compression force to the graphite carbon brush.

[0012] The grounding assembly includes a down conductor and a grounding plate. One end of the down conductor is connected to the A-arm through a terminal block. The grounding plate is installed at the other end of the down conductor and is connected to the motor protection grounding resistor.

[0013] The terminal at one end of the down conductor is a DT type copper terminal.

[0014] The down conductor is a soft copper down conductor.

[0015] The adjustable bracket is made of pure copper or copper alloy material, and the outer wall of the adjustable bracket is covered with an insulating paint layer or an insulating heat shrink tube sleeve.

[0016] The utility model has the following advantages:

[0017] 1. Improve safety: effectively prevent shaft current from damaging motor bearings and avoid potential safety accidents.

[0018] 2. Extend service life: Reduce bearing wear caused by shaft current and extend the overall service life of the motor.

[0019] 3. Reduce costs: The simple structure and readily available materials reduce the production and maintenance costs of tooling.

[0020] 4. Easy to install: The tooling is reasonably designed to facilitate installation and removal on the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the main structure of the utility model installed at the output end of the motor.

[0022] Figure 2 It is a structural schematic diagram of the tooling for eliminating shaft current of the utility model.

[0023] Figure 3 It is a structural schematic diagram of the carbon brush assembly of the utility model.

[0024] Figure 4 This utility model Figure 3 AA cross-sectional structural diagram.

[0025] Figure 5 It is a structural diagram of the compression clamp spring of the utility model. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0029] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "inner," "outer," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. These terms are only used to facilitate the description of the present invention and simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limitations on the present invention. In addition, if the terms "first," "second," etc. appear in the description of the present invention, they are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0030] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0031] As shown in the accompanying drawings, the utility model includes an adjustable bracket 1, a carbon brush assembly 2 and a grounding assembly 3.

[0032] The adjustable bracket 1 is installed on the motor output end housing, the carbon brush assembly 2 is installed on the adjustable bracket 1, the carbon brush assembly 2 is electrically connected to the adjustable bracket 1, one end of the grounding assembly 3 is electrically connected to the adjustable bracket 1, and the other end of the grounding assembly 3 is grounded.

[0033] The adjustable bracket 1 is composed of an A arm 4, a B arm 5 and a C arm 6. One end of the A arm 4 is mounted on the motor output end housing by bolts, one end of the B arm 5 is mounted on the middle part of the A arm 4 by bolts, the other end of the B arm 5 is mounted on the motor output end housing by bolts, and one end of the C arm 6 is mounted on the other end of the A arm 4 by bolts.

[0034] The carbon brush assembly 2 is mounted on the C arm 6 , and one end of the grounding assembly 3 is mounted on the A arm 4 .

[0035] The carbon brush assembly 2 includes a graphite carbon brush 7, a carbon brush box 8 and a compression retaining spring 9. The graphite carbon brush 7 is movably installed in the carbon brush box 8. When one end of the graphite carbon brush 7 contacts the outer wall of the motor power output shaft, the compression retaining spring 9 presses on the other end of the graphite carbon brush 7, so that the graphite carbon brush 7 is tightly attached to the outer wall of the motor power output shaft.

[0036] A carbon brush mounting groove 10 is provided in the middle of the carbon brush box 8. The graphite carbon brush 7 is located in the carbon brush mounting groove 10 and can slide back and forth along the carbon brush mounting groove 10. The graphite carbon brush 7 is electrically connected to the A arm 4 through a wire.

[0037] A retaining spring insertion groove 11 is provided at the bottom of the carbon brush box 8. The compression retaining spring 9 includes a V-shaped spring piece 12 and a coil spring 13. The coil spring 13 is installed on the top of the V-shaped spring piece 12 through rivets. The V-shaped spring piece 12 is inserted into the retaining spring insertion groove 11. The coil spring 13 is pressed against the end of the graphite carbon brush 7. The coil spring 13 continuously provides a pressing force to the graphite carbon brush 7.

[0038] The grounding assembly 3 includes a down conductor 14 and a grounding plate 15. One end of the down conductor 14 is connected to the A arm 4 through a terminal. The grounding plate 15 is installed at the other end of the down conductor 14. The grounding plate 15 is connected to the motor protection grounding resistor.

[0039] The connection terminal at one end of the down conductor 14 is a DT type copper terminal.

[0040] The down conductor 14 is a soft copper down conductor.

[0041] The adjustable bracket 1 is made of pure copper or copper alloy material, and the outer wall of the adjustable bracket 1 is covered with an insulating paint layer or an insulating heat shrink tube sleeve.

[0042] Example 1: As shown in the attached Figure 1As shown, the A-arm 4 and B-arm 5 of the adjustable bracket 1 are installed at the ends of the motor 100 housing at angles of 30, 45, or 60 degrees, depending on the housing model of the motor 100. They are secured with M6-M24 screws and torque tested with a torque wrench to ensure compliance with national standards. The A-arm 4 and B-arm 5 are bolted together; loosening the bolts allows for adjustment of the angle. The carbon brush assembly 2 is mounted on the A-arm 4 via the C-arm 6. The angle of the C-arm 6 is adjusted according to the position of the motor 100's power output shaft and secured with bolts. The graphite carbon brush 7 is held in close contact with the outer wall of the motor 100's power output shaft. A coil spring 13 provides continuous pressure to the graphite carbon brush 7, ensuring good contact during rotation of the motor 100's power output shaft, reducing contact resistance and effectively transmitting shaft current. A clearance of 0.1-0.3 mm is maintained between the graphite carbon brush 7 and the inner wall of the brush mounting slot 10 to prevent excessive clearance and wobbling. The unit pressure of the graphite carbon brush 7 should be selected according to the "Carbon Brush Technical Performance Table." For motors 100 with higher speeds or those operating under vibration, the unit pressure should be appropriately increased to ensure proper operation. To ensure that the carbon brushes do not overheat, spark, make low noise, or break, the median unit pressure of the graphite carbon brush 7 is 0.4-0.6 kgf / cm². The graphite carbon brush 7 effectively directs the shaft current generated by the motor shaft into the grounding assembly 3. When installing the down conductor 14 on the terminal block, use a wire crimping tool to crimp the terminal block to ensure a stable connection between the wire conductor and the metal portion inside the terminal block. The crimping force should be determined based on the model and specifications of the terminal block. Avoid overtightening or overloosening, which can lead to poor connection or damage to the terminal block. Ensure that the contact area between the down conductor 14 and the terminal block is clean, dry, and free of oil, dirt, and oxidation to ensure a stable and reliable electrical connection. During connection, the electrical resistance measured by an electrical test should be no greater than 4 ohms.

Claims

1. A tool for eliminating shaft current of a three-phase asynchronous motor, characterized in that: It includes an adjustable bracket (1), a carbon brush assembly (2) and a grounding assembly (3), The adjustable bracket (1) is mounted on the motor output end housing, the carbon brush assembly (2) is mounted on the adjustable bracket (1), the carbon brush assembly (2) is electrically connected to the adjustable bracket (1), one end of the grounding assembly (3) is electrically connected to the adjustable bracket (1), and the other end of the grounding assembly (3) is grounded; the adjustable bracket (1) is composed of an A arm (4), a B arm (5) and a C arm (6), one end of the A arm (4) is mounted on the motor output end housing by a bolt, one end of the B arm (5) is mounted on the middle of the A arm (4) by a bolt, the other end of the B arm (5) is mounted on the motor output end housing by a bolt, and one end of the C arm (6) is mounted on the other end of the A arm (4) by a bolt.

2. The tool for eliminating shaft current of a three-phase asynchronous motor according to claim 1, characterized in that: The carbon brush assembly (2) is mounted on the C arm (6), and one end of the grounding assembly (3) is mounted on the A arm (4).

3. The tool for eliminating shaft current of a three-phase asynchronous motor according to claim 2, characterized in that: The carbon brush assembly (2) comprises a graphite carbon brush (7), a carbon brush box (8) and a compression spring (9). The graphite carbon brush (7) is movably installed in the carbon brush box (8). When one end of the graphite carbon brush (7) contacts the outer wall of the motor power output shaft, the compression spring (9) presses on the other end of the graphite carbon brush (7), so that the graphite carbon brush (7) is closely attached to the outer wall of the motor power output shaft.

4. The tool for eliminating shaft current of a three-phase asynchronous motor according to claim 3, characterized in that: A carbon brush installation groove (10) is provided in the middle of the carbon brush box (8), and the graphite carbon brush (7) is located in the carbon brush installation groove (10) and can slide back and forth along the carbon brush installation groove (10). The graphite carbon brush (7) is electrically connected to the A arm (4) through a wire.

5. The tool for eliminating shaft current of a three-phase asynchronous motor according to claim 4, characterized in that: A retaining spring insertion groove (11) is provided at the bottom of the carbon brush box (8), and the compression retaining spring (9) includes a V-shaped spring piece (12) and a coil spring (13). The coil spring (13) is installed on the top of the V-shaped spring piece (12) through a rivet. The V-shaped spring piece (12) is inserted into the retaining spring insertion groove (11). The coil spring (13) is pressed against the end of the graphite carbon brush (7), and the coil spring (13) continuously provides a pressing force to the graphite carbon brush (7).

6. The tool for eliminating shaft current of a three-phase asynchronous motor according to claim 5, characterized in that: The grounding assembly (3) comprises a down conductor (14) and a grounding plate (15). One end of the down conductor (14) is connected to the A arm (4) via a terminal block. The grounding plate (15) is installed at the other end of the down conductor (14). The grounding plate (15) is connected to the motor protective grounding resistor.

7. The tool for eliminating shaft current of a three-phase asynchronous motor according to claim 6, characterized in that: The connection terminal at one end of the down conductor (14) is a DT type copper terminal.

8. The tool for eliminating shaft current of a three-phase asynchronous motor according to claim 7, characterized in that: The down conductor (14) is a soft copper down conductor.

9. The tool for eliminating shaft current of a three-phase asynchronous motor according to claim 8, characterized in that: The adjustable bracket (1) is made of pure copper or copper alloy material, and the outer wall of the adjustable bracket (1) is covered with an insulating paint layer or an insulating heat shrink tube sleeve.

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