Combined conducting ring and use method thereof

Abstract

The invention relates to a combined conducting ring and a use method thereof.The conducting ring is mainly composed of an upper conducting strip, a lower conducting strip and a middle supporting spring, in the installation process, the conducting ring is assembled in a corresponding groove position in a motor shaft, after installation is completed, due to the effect of the supporting spring, the inner peripheries of the upper conducting strip and the lower conducting strip are opened, and the inner peripheries of the upper conducting strip and the lower conducting strip are sealed. Therefore, the side face of the conducting strip is tightly attached to the motor shaft, the periphery of the conducting strip is tightly contacted with the shell, and a stable conducting path is formed between the motor shaft and the shell. According to the motor, bearing voltage is formed on the inner ring and the outer ring of a bearing due to the existence of common-mode voltage, in addition, common-mode current generated by the common-mode voltage also flows through the motor bearing, so that the problems of electric discharge, pits, spots and the like of the bearing are caused at the motor bearing, and an effective solution is provided aiming at the conditions. Through the combined conducting ring, the bearing voltage can be effectively conducted to the shell, so that the bearing electrocorrosion is avoided, and the normal operation and the service life of the motor are ensured.

Description

Technical Field

[0001] The invention relates to the field of motor grounding, and in particular to a combined conductive ring and a use method thereof. Background Art

[0002] The AC power operated by the variable frequency drive (VFD) uses pulse width modulation (PWM) to control the motor speed. This means that due to the existence of common mode voltage, the motor will form bearing voltage on the inner and outer rings of the bearings. In addition, the common mode current generated by the common mode voltage will also flow through the motor bearings, and then discharge on the motor bearings, causing EDM pits, electrical corrosion spots and groove damage, resulting in unexpected downtime and repair costs.

[0003] Therefore, motors running with VFD or DC drives must be equipped with bearing protection devices, that is, conductive rings, to conduct the current in the motor to prevent these two currents from damaging the bearings. Summary of the invention

[0004] The main purpose of the present invention is to provide a combined conductive ring and a method for using the same, which solves the problem of electric spark discharge at the motor shaft bearing causing electrical corrosion of the bearing due to the existence of common mode voltage during the operation of a motor operated by a VFD or a DC drive.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a combined conductive ring, including an intermediate support spring, which is used to be installed on the motor shaft. Removable conductive sheets are provided on both sides of the intermediate support spring, the inner periphery of the conductive sheet abuts against the intermediate support spring, the outer periphery of the conductive sheet abuts against the motor housing, and the side surface of the conductive sheet abuts against the motor shaft.

[0006] In a preferred embodiment, a mounting groove is provided on the motor shaft, and the middle support spring is sleeved in the mounting groove. One side of the conductive sheet abuts against the side wall of the mounting groove, and the other side abuts against the middle support spring in a sliding manner.

[0007] In a preferred embodiment, the conductive sheet is connected to the motor housing, and the motor housing is provided with a ground wire for grounding.

[0008] In the preferred embodiment, the middle support spring is an open-loop annular corrugated spring, and a palm-jointing portion is provided at the open loop of the middle support spring, so that the palm-jointing portion facilitates the middle support spring to be connected end to end; The conductive sheet is an open-loop annular thin sheet.

[0009] In the preferred embodiment, the top of the wave crest and trough of the middle support spring is provided with a groove, one side of the groove is provided with a supporting portion, and the other side is provided with a supporting portion; The top of the supporting part is a plane, and the supporting part is used to place the conductive sheet. The top of the abutting part is a semicircular surface, and the top of the abutting part is higher than the top of the supporting part.

[0010] In a preferred embodiment, an arc surface is provided on the inner side of the arc of the conductive sheet, and a plane is provided on the outer side of the arc of the conductive sheet. The arc surface is used to abut against the abutting surface, and the plane abuts against the motor housing.

[0011] In a preferred embodiment, the conductive sheet is placed on the support portion, and there is a gap between the conductive sheet and the groove.

[0012] In a preferred embodiment, a side of the abutting portion facing the groove is provided with an abutting surface, and a certain angle A is formed between the abutting surface and the bottom surface of the groove, and the angle A is 10 degrees to 20 degrees; The thickness of the conductive sheet is 0.35 mm to 0.5 mm.

[0013] In a preferred embodiment, the angle A is 10 degrees, and the thickness of the conductive sheet is 0.35 mm.

[0014] A method for using the combined conductive ring described above includes: S1. Place the middle support spring in the installation groove; S2. Place the conductive sheet on both sides of the middle support spring, with one side of the conductive sheet abutting against the inner wall of the mounting groove and the other side slidingly abutting against the middle support spring; S3, the motor housing outside the conductive sheet abuts against the motor housing, and the motor housing clamps the conductive sheet, so that the open loop of the conductive sheet and the middle support spring shrinks and closes; S4. When the motor shaft rotates, the conductive sheet is supported by the abutment surface of the middle support spring, so that the outer circular plane of the conductive sheet is in close contact with the inner wall of the motor housing, and the side surface of the conductive sheet is in close contact with the inner wall of the mounting groove; S5. The shaft voltage generated when the motor shaft rotates is transmitted to the motor housing through the conductive sheet, and the shaft voltage is released by the ground wire.

[0015] The present invention provides a combined conductive ring and a method for using the same, which have the following beneficial effects: 1. The combined conductive ring uses the coordinated work of the middle support spring, the conductive sheet and the grounding ring (or the housing) to effectively conduct the shaft voltage generated when the motor shaft rotates to the outside of the motor, avoiding the shaft voltage from discharging on the motor bearings, thereby preventing the motor from unexpectedly shutting down due to EDM pits, electrical corrosion spots and groove damage, greatly reducing maintenance costs, significantly extending the service life of the motor bearings, and ensuring the stable operation of the motor; 2. In this structure, the conductive sheet is placed on the support part, and the inner periphery is in contact with the abutment surface. The abutment surface is provided with an inclined surface with an angle of 10°-20°, which provides support force for the side surface of the conductive sheet and the end surface of the shaft groove, and the outer periphery and the shell. Under the action of this support force, it can always maintain a good fit with the grounding ring and the inner wall of the installation groove, ensuring the stability and reliability of the shaft voltage transmission, and improving the overall conductivity and working efficiency of the conductive ring; 3. Compared with the traditional carbon brush conductive ring, the combined conductive ring used in this structure has a lower-cost manufacturing process and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 is an isometric view of the conductive ring of the present invention; Figure 2 is an isometric view of the intermediate support spring of the present invention; Figure 3 is a cross-sectional view of a conductive sheet of the present invention; Figure 4 is a side view of the conductive ring of the present invention; Figure 5 It is a partial view of the middle support spring of the present invention; Figure 6 It is a partial isometric view of the intermediate support spring of the present invention; Figure 7 is a cross-sectional view of the intermediate support spring of the present invention; Figure 8 is a schematic diagram of the angle A of the present invention; Fig. 9 It is a schematic diagram of the assembly of the conductive ring of the present invention; Fig.10 It is a partial view of the conductive ring assembly of the present invention; Fig.11 is a schematic diagram of a circuit for generating a common mode voltage according to the present invention; Fig.12 It is a schematic diagram of voltage change of the present invention; Fig.13 is a schematic diagram of a common mode voltage loop of the present invention; Fig.14 is a schematic diagram of bearing corrosion of the present invention; Fig.15 It is a schematic diagram of the corrosion pattern of the bearing of the present invention; Fig.16 This is a schematic diagram of the current conduction of the conductive ring of the present invention; Fig.17 It is a schematic diagram of deriving the conductive ring current of the present invention.

[0017] In the figure: the middle support spring 1; the palm-joining part 101; the groove 102; the abutting part 103; the supporting part 104; the abutting surface 105; the conductive sheet 2; the arc surface 201; the plane 202; the motor shaft 3; the mounting groove 301; the motor housing 4; the ground wire 5. DETAILED DESCRIPTION

[0018] Example 1 like Figure 1-10As shown, a combined conductive ring includes an intermediate support spring 1, which is used to be installed on a motor shaft 3. Removable conductive sheets 2 are provided on both sides of the intermediate support spring 1. The inner periphery of the conductive sheet 2 abuts against the intermediate support spring 1, the outer periphery of the conductive sheet 2 abuts against the motor housing 4, and the side surface of the conductive sheet 2 abuts against the motor shaft 3.

[0019] In the preferred embodiment, a mounting groove 301 is provided on the motor shaft 3 , and the middle support spring 1 is sleeved in the mounting groove 301 . One side of the conductive sheet 2 abuts against the side wall of the mounting groove 301 , and the other side abuts against the middle support spring 1 in a sliding manner.

[0020] In a preferred embodiment, the conductive sheet 2 is connected to the motor housing 4, and the motor housing 4 is provided with a ground wire 5 for grounding.

[0021] In the preferred embodiment, the middle support spring 1 is an open-loop annular corrugated spring, and a palm-joining portion 101 is provided at the open loop of the middle support spring 1, and the palm-joining portion 101 facilitates the middle support spring 1 to be connected end to end; The conductive sheet 2 is an open-loop annular thin sheet.

[0022] In the preferred embodiment, a groove 102 is provided at the top of the wave crest and trough of the middle support spring 1, a support portion 104 is provided on one side of the groove 102, and a supporting portion 103 is provided on the other side; The top of the supporting portion 104 is a plane, and the supporting portion 104 is used to place the conductive sheet 2 . The top of the abutting portion 103 is a semicircular surface, and the top of the abutting portion 103 is higher than the top of the supporting portion 104 .

[0023] In a preferred embodiment, an arc surface 201 is provided on the inner side of the arc of the conductive sheet 2 , and a plane 202 is provided on the outer side of the arc of the conductive sheet 2 . The arc surface 201 is used to abut against the abutting surface 105 , and the plane 202 abuts against the motor housing 4 .

[0024] In a preferred solution, the conductive sheet 2 is placed on the support portion 104 , and there is a gap between the conductive sheet 2 and the groove 102 .

[0025] In the preferred embodiment, abutment surface 105 is provided on one side of the abutment portion 103 facing the groove 1, and a certain angle A is formed between the abutment surface 105 and the bottom surface of the groove 102, and the angle A is 10 to 20 degrees; The thickness of the conductive sheet 2 is 0.35 mm to 0.5 mm.

[0026] In a preferred embodiment, the angle A is 10 degrees, and the thickness of the conductive sheet 2 is 0.35 mm.

[0027] Example 2 Further illustrate with reference to Example 1, Figure 9-10 The structure shown in FIG. 1 is applied with the above-mentioned method for using a multi-layer conductive ring, the method comprising: S1, placing the middle support spring 1 in the installation groove 301; S2, placing the conductive sheet 2 on both sides of the middle support spring 1, with one side of the conductive sheet 2 abutting against the inner wall of the mounting groove 301, and the other side slidingly abutting against the middle support spring 1; S3, the outer side of the conductive sheet 2 abuts against the motor housing 4, and the motor housing 4 clamps the conductive sheet 2, so that the open loop of the conductive sheet 2 and the middle support spring 1 shrinks and closes; S4, when the motor shaft 3 rotates, the conductive sheet 2 is supported by the abutting surface 105 of the intermediate support spring 1, so that the outer circular plane 202 of the conductive sheet 2 is in close contact with the inner wall of the motor housing 4, and the outer side of the conductive sheet 2 is in close contact with the inner wall of the mounting groove 301; S5. The shaft voltage generated when the motor shaft 3 rotates is transmitted to the motor housing 4 through the conductive sheet 2, thereby completing the release of the shaft voltage.

[0028] Example 3 Further illustrate with reference to Example 1, Figure 3 In the structure shown, the conductive sheet 2 is made of high-performance PEEK conductive resin. The loss calculation method of the combined conductive ring on the motor power and torque loss is as follows: 1. (When an ideal sphere contacts a plane, the contact surface radius is Contact force When elastic deformation , during plastic deformation ); 2. ; 3. ; 4. ( is the contact resistance, in units of ; is the material coefficient; It’s pressure; It is a contact form, point contact , line contact , face contact ) Assuming that the supporting force Ft of the middle supporting spring 1 on the conductive sheet 2 is 12N, when the angle of the abutting surface 105 is 10°, the resultant force Fn=Ft*sin10°=2N; When n=20000rpm, the outer diameter of the conductive sheet 2 is 50mm, and the friction coefficient u (peek) of the conductive sheet 2 is 0.24, The torque loss of the motor is: T₋loss=u * Fn * R=0.012Nm The power loss of the motor is: P₋loss =T・n / 9549=25.1w When the motor power is 70 kW or more, when the angle of the abutment surface 105 is 10°, the power loss can be reduced to less than 0.035%, that is, the angle of 10° is judged to be an appropriate angle.

[0029] Embodiment 4, as Figure 11-12 As shown, the inverter uses switches to block the DC output and convert it into pulse voltages of equal amplitude and unequal width to equal sinusoidal AC. The neutral point voltage of the stator winding of traditional three-phase AC is zero, while for PWM variable frequency motor, the neutral point voltage of the stator winding is not zero at any time. The non-zero voltage to the ground of the neutral point is the common mode voltage of the motor.

[0030] like Fig.13 As shown, 1. There are electrostatic capacities between the motor rotor and stator, stator and winding, and winding and rotor, which are Csr, Cws, and Cwr respectively. The common mode voltage is divided layer by layer under these capacitive components, thus forming a capacitance Cb at the inner and outer rings of the bearing to generate a potential difference. Since the bearing cannot maintain a stable gap during rotation, it causes the phenomenon of power on or discharge.

[0031] 2. Under common mode voltage, common mode current will be generated when the winding, stator, and the earth form a loop. This high-frequency common mode current induces high-frequency magnetic flux, and the high-frequency voltage induced at both ends of the rotor flows in the direction of: one end of the rotor → bearing → stator → bearing → the other end of the rotor, forming a loop, such as Fig.13 As shown by the red arrow, shaft current is generated and flows through the bearing.

[0032] 3. From winding → rotor → bearing → housing → earth, such as Fig.13 As shown by the yellow arrow, when a loop is formed, a bearing current component will flow through the bearing.

[0033] like Figure 14-15 As shown, the bearing electrical corrosion mechanism: 1. The bearing consists of an inner ring, an outer ring and rolling elements. When the bearing is running, due to the presence of lubricant, a capacitor is formed.

[0034] 2. Under the above common mode voltage, a potential difference is generated at both ends of the bearing, and the grease performs a blocking operation. When the potential difference reaches a certain value, it will break through the capacitor and cause spark discharge.

[0035] 3. At this time, the local temperature rises, the grease carbonizes, and the bearing surface melts.

[0036] 4. The melting point is pulled apart during rolling, forming corrosion phenomena such as pits.

[0037] like Figure 16-17As shown, the current conduction process of the scheme of the present invention is as follows: the conductive ring is installed at one end of the motor shaft 3, and the current flows to the side of the conductive sheet 2 and the outer periphery of the conductive sheet 2 through the end face of the installation groove 301, and then flows from the outer periphery of the conductive sheet 2 to the motor housing 4 to form a loop, reducing the potential difference at both ends of the bearing, thereby protecting the bearing from electrical corrosion.

[0038] Considering the application trend of high motor speed and peak value ≧20000rpm, a high wear-resistant material with conductive properties, PEEK resin material, is developed. The conductive properties of the material are evaluated as follows: We use the Japanese standard JIS-K7194-1994 four-probe method to evaluate the conductivity of resin materials. The measurement index is surface resistivity. .

[0039] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A combined conductive ring, characterized in that: The invention comprises an intermediate support spring (1), wherein detachable conductive sheets (2) are provided on both sides of the intermediate support spring (1), the inner periphery of the conductive sheet (2) abuts against the intermediate support spring (1), the outer periphery of the conductive sheet (2) abuts against the motor housing (4), and the side surface of the conductive sheet (2) abuts against the motor shaft (3).

2. A combined conductive ring according to claim 1, characterized in that: The motor shaft (3) is provided with a mounting groove (301), the middle support spring (1) is sleeved in the mounting groove (301), one side of the conductive sheet (2) abuts against a side wall of the mounting groove (301), and the other side abuts against the middle support spring (1) in a sliding manner.

3. The combined conductive ring according to claim 1, characterized in that: The conductive sheet (2) is connected to the motor housing (4), and the motor housing (4) is provided with a ground wire (5) for grounding.

4. The combined conductive ring according to claim 1, characterized in that: The middle support spring (1) is an open-loop annular corrugated spring, and a palm-jointing portion (101) is provided at the open loop of the middle support spring (1), and the palm-jointing portion (101) facilitates the middle support spring (1) to be connected end to end; The conductive sheet (2) is an open-loop annular thin sheet.

5. The combined conductive ring according to claim 1, characterized in that: A groove (102) is provided at the top of the wave crest and trough of the middle support spring (1); a support portion (104) is provided on one side of the groove (102) and a supporting portion (103) is provided on the other side; The top of the support portion (104) is a plane, and the support portion (104) is used to place the conductive sheet (2); the top of the abutment portion (103) is a semicircular surface, and the top of the abutment portion (103) is higher than the top of the support portion (104).

6. The combined conductive ring according to claim 5, characterized in that: An arc surface (201) is provided on the inner side of the arc of the conductive sheet (2), and a plane (202) is provided on the outer side of the arc of the conductive sheet (2). The arc surface (201) is used to abut against the abutting surface (105), and the plane (202) abuts against the motor housing (4).

7. A combined conductive ring according to claim 6, characterized in that: The conductive sheet (2) is placed on the support portion (104), and a gap exists between the conductive sheet (2) and the groove (102).

8. The combined conductive ring according to claim 5, characterized in that: A side of the abutting portion (103) facing the groove (1) is provided with an abutting surface (105), and a certain angle A is formed between the abutting surface (105) and the bottom surface of the groove (102), and the angle A is in the range of 10 to 20 degrees.

9. The combined conductive ring according to claim 8, characterized in that: The angle A is 10 degrees, and the thickness of the conductive sheet (2) is 0.35 mm.

10. A method for using a combined conductive ring according to any one of claims 1 to 9, characterized in that: The method includes: S1. Place the middle support spring (1) in the mounting groove (301); S2, placing the conductive sheet (2) on both sides of the middle support spring (1), with one side of the conductive sheet (2) abutting against the inner wall of the mounting groove (301), and the other side slidingly abutting against the middle support spring (1); S3, the motor housing outside the conductive sheet (2) abuts against the motor housing (4), and the motor housing (4) clamps the conductive sheet (2), so that the open loop of the conductive sheet (2) and the middle support spring (1) shrinks and closes; S4, when the motor shaft (3) rotates, the conductive sheet (2) is supported by the abutment surface (105) of the intermediate support spring (1), so that the outer circular plane (202) of the conductive sheet (2) is in close contact with the inner wall of the motor housing (4), and the side surface of the conductive sheet (2) is in close contact with the inner wall of the mounting groove (301); S5. The shaft voltage generated when the motor shaft (3) rotates is transmitted to the motor housing (4) through the conductive sheet (2), and the shaft voltage is released by the ground wire (5).

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