A new energy automobile motor bearing voltage non-contact active elimination topology structure and its suppression method

Abstract

The application provides a new energy automobile motor bearing voltage non-contact active elimination topology structure and a suppression method thereof.The application injects an opposite-phase voltage into a bearing voltage coupling path in a motor through a common-mode transformer to eliminate the bearing voltage, and then eliminates the electric corrosion problem.The common-mode transformer takes a motor rotating shaft as a secondary single-turn winding, and the common-mode transformer and the motor rotating shaft do not have mechanical contact.The suppression method can effectively eliminate the motor bearing voltage, the bearing no longer has a discharge breakdown phenomenon, and the bearing electric corrosion problem can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle motor bearing electro-corrosion suppression technology, and in particular to a non-contact active elimination topology for voltage in new energy vehicle motor bearings and its suppression method. Background Technology

[0002] As new energy vehicles develop towards higher voltage and higher power density, the widespread application of 800V high-voltage platforms and SiC power devices has led to increasingly serious bearing electro-corrosion problems in drive motor systems. Statistics show that over 40% of motor failures originate from rolling bearing failures, with electro-corrosion becoming one of the main failure modes. In motor systems driven by high-voltage SiC inverters, the bearing voltage and bearing current generated by the coupling of common-mode voltage, high-frequency switching noise, and bearing parasitic parameters can cause "washboard pattern" electro-erosion damage on the bearing raceway, leading to serious consequences such as abnormal noise, increased vibration, and even bearing seizure.

[0003] The current response strategies of the new energy vehicle industry can be divided into the following two categories:

[0004] Insulation-blocking bearings, such as ceramic ball bearings or ceramic-coated bearings, can block the current path. However, ceramic materials are brittle and prone to fracture under high-speed impact loads. These fragments accelerate raceway wear. The insulating coating is also prone to peeling off under long-term mechanical friction, creating localized current concentrations in the peeling areas, which exacerbates the synergistic damage of electro-erosion and wear. Although ceramic ball bearings can block bearing current, bearing voltage still exists and may leak into the motor housing through other non-insulated bearings. For example, it can form a circuit through the bearings and gears in the reducer, causing electro-erosion problems in the reducer bearings and gears.

[0005] Conductive venting components include conductive carbon brushes and grounding rings. Sliding friction occurs when the carbon brush contacts the rotating shaft, resulting in a mechanical wear rate as high as 0.1-0.3 mm / 1000 hours. The metal / carbon dust generated by this wear contaminates the lubrication system, leading to bearing lubrication failure and abrasive wear. Furthermore, uneven carbon brush pressure can cause localized overheating at the contact surface, further accelerating electrochemical corrosion. Currently, the rotational speed of new energy vehicles has exceeded 20,000 r / min. High speeds accelerate the mechanical wear of conductive rings, leading to increased contact resistance and reduced voltage venting from the bearing. This suppression effect is particularly poor in demanding applications involving high oil temperatures, high speeds, and high voltages.

[0006] In summary, existing solutions for bearing electro-corrosion all rely on physical contact conduction or blocking. Their inherent mechanical wear problems not only fail to eradicate electro-corrosion, but also accelerate the compound damage to the bearing. During long-term operation of the motor, the suppression effect is not ideal. Summary of the Invention

[0007] The purpose of this invention is to solve the problems in the prior art and proposes a non-contact active elimination method for topology of bearing voltage in new energy vehicle motors and its suppression method.

[0008] This invention is achieved through the following technical solution: This invention proposes a non-contact active voltage elimination topology for bearings in new energy vehicle motors. The topology includes a motor controller, a common-mode transformer, and a power compensation circuit. The motor controller is connected to the power compensation circuit, and the power compensation circuit is connected to the common-mode transformer. The topology injects a reverse voltage V into the bearing voltage coupling path inside the motor through the common-mode transformer. inject Eliminating bearing voltage V b The reverse voltage V inject It consists of four-level stepped wave voltages with equal amplitude and opposite phase; the common-mode transformer uses the motor shaft as a single-turn winding on the secondary side, and there is no mechanical contact between the common-mode transformer and the motor shaft.

[0009] Furthermore, the power compensation circuit includes four power switching transistors Q7, Q8, Q9, and Q10. 10 It has four independent DC power supplies and two independent DC buses, referred to as the first DC bus and the second DC bus, respectively. The first DC bus forms a circuit with power switches Q7 and Q8, and the second DC bus forms a circuit with power switches Q9 and Q1. 10 A circuit is formed.

[0010] Furthermore, two identical DC power supplies are connected in series on the first DC bus, with the voltage of the power supply on the first DC bus denoted as V1. Similarly, two identical DC power supplies are connected in series on the second DC bus, with the voltage of the power supply on the second DC bus denoted as V2. The values ​​of V1 = 2V2 = U / 3, where U is the bearing voltage. b The amplitude.

[0011] Furthermore, the common-mode transformer is a magnetic winding group CMT1 and CMT2 on the motor shaft. The magnetic winding group CMT1 includes a1 end and b1 end, and the magnetic winding group CMT2 includes a2 end and b2 end, wherein the two magnetic winding groups are connected in parallel.

[0012] Furthermore, the four power switches Q7, Q8, Q9, Q... 10 The bridge consists of two arms. The first arm includes Q7 and Q8, with point D at its midpoint. Point D is connected to ends a1 and a2 of the magnetic winding assembly. The second arm includes Q9 and Q8. 10 The midpoint of the bridge arm is point E, which is connected to the b1 and b2 ends of the magnetic winding assembly.

[0013] Furthermore, terminals a1 and a2 of the magnetic ring are designated as terminal A; terminals b1 and b2 of the magnetic ring are designated as terminal B; and terminal A is taken as the positive voltage reference terminal of the magnetic ring, with a voltage of V. A Terminal B of the magnetic ring serves as the negative voltage reference terminal for the magnetic ring, and its voltage is V. B .

[0014] Furthermore, the motor controller outputs four PWM signals: PWM7, PWM8, PWM9, and PWM1. 10 These correspond to the four power switching transistors Q7, Q8, Q9, and Q1 connected to the power compensation circuit, respectively. 10 Through four power switching transistors Q7, Q8, Q9, Q... 10 The timing control, combined with the power supply configuration of V1=2V2=U / 3, enables V A V B A specific combination of potentials is generated, which ultimately synthesizes a four-level stepped waveform containing ±U / 2 and ±U / 6, i.e., an inverted voltage V, across the common-mode transformer. inject .

[0015] Furthermore, the carrier period T of the four PWM control signals output by the motor controller is related to the bearing voltage V at one end of the motor. b1 The PWM cycle is strictly synchronized; the voltage signal synthesized across the common-mode transformer is V. inject It should be a four-level stepped wave shape, with amplitude and V. b1 They are the same but opposite in phase.

[0016] Furthermore, the motor controller employs an independent master controller.

[0017] This invention also proposes a suppression method based on the aforementioned topology, the suppression method comprising four operating modes: in the first operating mode, corresponding to times t0~t1 and t7~t8, Q7, Q 10 With the circuit open and all others closed, the output at point D of the first bridge arm is +U / 3, which is applied to terminal A of the magnetic ring. The output at point E of the second bridge arm is -U / 6, which is applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage V across the magnetic ring is... AB =V A -V B =(+U / 3)-(-U / 6)=+U / 2, forming the first level; In the second operating mode, corresponding to times t1~t2 and t6~t7, Q7 and Q9 are turned on, and the others are turned off. Point D of the first bridge arm outputs +U / 3, which is applied to terminal A of the magnetic ring, and point E of the second bridge arm outputs +U / 6, which is applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage across the magnetic ring is +U / 6, forming the second level; In the third operating mode, corresponding to times t2~t3 and t5~t6, Q8 and Q9 are turned on, and the voltage across the magnetic ring is +U / 6, forming the second level. 10When the first bridge arm is turned on and the others are turned off, point D of the first bridge arm outputs -U / 3, which is applied to terminal A of the magnetic ring. Point E of the second bridge arm outputs -U / 6, which is applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage across the magnetic ring is -U / 6, forming the third level. In the fourth working mode, corresponding to times t3 to t5, Q8 and Q9 are turned on and the others are turned off. Point D of the first bridge arm outputs -U / 3, which is applied to terminal A of the magnetic ring. Point E of the second bridge arm outputs +U / 6, which is applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage across the magnetic ring is -U / 2, forming the fourth level.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. Good inhibitory effect:

[0020] The voltage cancellation method can completely eliminate the motor bearing voltage, thoroughly eliminate EDM discharge-type bearing current, and fundamentally solve the problem of bearing electro-corrosion.

[0021] 2. Advantages of contactless design:

[0022] It completely avoids the mechanical wear problems of traditional contact solutions such as carbon brushes, ensuring long-term operational reliability; the innovative design of using the motor shaft as the secondary side of the transformer achieves efficient energy coupling without direct contact with the power circuit, resulting in higher system safety.

[0023] 3. Advantages of low-pressure, small-size design:

[0024] Since the compensation circuit and common mode transformer cancel out the motor bearing voltage with a voltage amplitude of only a few tens of volts, rather than the motor common mode voltage with a large amplitude, the required compensation circuit components have low voltage and current stress, and the magnetic ring of the common mode transformer is also small in size, making it easy to integrate into the design. The common mode transformer can be integrated into the motor end cover, and the compensation circuit can be integrated into the motor controller circuit.

[0025] 4. Strong application scalability:

[0026] It is not only applicable to the protection of bearings inside motors, but can also be extended to the protection of electrical corrosion of external mechanical loads (such as reducer bearings and gears).

[0027] This invention, through innovative non-contact voltage cancellation technology, solves key problems of existing technologies such as mechanical wear, system complexity, and limited applicability while ensuring high-efficiency suppression, providing a brand-new solution for bearing electro-corrosion protection. Attached Figure Description

[0028] 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 only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0029] Figure 1 This is a topology diagram of a non-contact active voltage elimination method for motor bearings in new energy vehicles, as described in this invention.

[0030] Figure 2 The voltage V of the original bearing on one side of the motor b1 Waveform diagram.

[0031] Figure 3 It is the injected voltage V that is output to both sides of one of the magnetic rings CMT1 via the power compensation circuit. inject Waveform diagram.

[0032] Figure 4 This is achieved by controlling the primary winding of CMT1 to inject a voltage V that is equal in size and opposite in phase to the bearing voltage. inject Injecting coupling loop to cancel V b1 The bearing voltage V on the rear side of the motor is now present. b_c1 Waveform diagram.

[0033] Figure 5 This is a cross-sectional view of a common-mode transformer (selecting one of the magnetic rings). Detailed Implementation

[0034] 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. 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.

[0035] To address the shortcomings of the aforementioned technologies, this invention proposes a non-contact active elimination topology for bearing voltage in new energy vehicle motors and a method for suppressing it. This method involves injecting a reverse voltage into the bearing voltage coupling path inside the motor using a common-mode transformer to cancel the bearing voltage, thereby eliminating the electro-corrosion problem. The common-mode transformer uses the motor shaft as a single-turn secondary winding, and there is no mechanical contact between the common-mode transformer and the motor shaft. The proposed suppression method effectively eliminates the bearing voltage, preventing discharge breakdown in the bearing and effectively solving the bearing electro-corrosion problem.

[0036] Figure 1This is a schematic diagram of the topology of the present invention, which includes a power compensation circuit and two toroidal common-mode transformers CMT1 and CMT2. The compensation circuit has two independent DC buses, referred to as the first DC bus and the second DC bus. Two identical DC power supplies, V1 and V2, are connected in series on each of the first and second DC buses, with an amplitude of V1 = 2V2. The midpoint of the series connection of each DC bus is connected to the same ground. The motor controller outputs PWM1 to PWM6 signals to the drive circuit, causing the motor to generate a bearing voltage V at one end of the motor. b1 Since the winding assemblies at both ends of the common-mode transformer are connected in parallel, only one end needs to be discussed here; the other end is the same. Therefore, this discussion focuses only on the bearing voltage V at one end of the motor. b1 Please explain the cancellation process, such as... Figure 2 As shown; the motor controller outputs PWM7~PWM 10 The signal is given to the power compensation circuit; and in order to cancel out V b1 The common-mode transformer generates the injection voltage V. inject Must be with V b1 Equal amplitude and opposite phase, such as Figure 3 As shown.

[0037] Specifically, in combination Figures 1-5 This invention proposes a non-contact active voltage cancellation topology for bearings in new energy vehicle motors. The topology includes a motor controller, a common-mode transformer, and a power compensation circuit. The motor controller is connected to the power compensation circuit, which in turn is connected to the common-mode transformer. The topology injects a reverse voltage V into the bearing voltage coupling path inside the motor through the common-mode transformer. inject Eliminate the bearing voltage V at one end of the motor b1 The reverse voltage V inject A four-level stepped-wave voltage with equal amplitude and opposite phase is used to precisely cancel out the original signal, thereby effectively suppressing voltage fluctuations. The topology diagram of this power compensation circuit is shown in the attached figure. Figure 1 As shown; the common-mode transformer uses the motor shaft as a single-turn secondary winding, and there is no mechanical contact between the common-mode transformer and the motor shaft. The canceled bearing voltage V... b1 The motor controller outputs a four-level stepped voltage (+U / 2, +U / 6, -U / 6, -U / 2) through PWM modulation of the switching transistors (Q1-Q6), as shown in the waveform diagram below. Figure 2 As shown.

[0038] The power compensation circuit includes four power switching transistors Q7, Q8, Q9, and Q1. 10It has four independent DC power supplies and two independent DC buses, referred to as the first DC bus and the second DC bus, respectively. Two identical DC power supplies are connected in series on each of the first and second DC buses. The first DC bus forms a loop with power switches Q7 and Q8, and the second DC bus forms a loop with power switches Q9 and Q1. 10 A circuit is formed.

[0039] The voltage of the power supply on the first DC bus is V1, and the voltage of the power supply on the second DC bus is V2. Numerically, V1 = 2V2 = U / 3, where U is the bearing voltage. b The amplitude.

[0040] Furthermore, the common-mode transformer is a magnetic winding group CMT1 and CMT2 on the motor shaft. The magnetic winding group CMT1 includes a1 end and b1 end, and the magnetic winding group CMT2 includes a2 end and b2 end, wherein the two magnetic winding groups are connected in parallel.

[0041] The four power switching transistors Q7, Q8, Q9, Q 10 The bridge consists of two arms. The first arm includes Q7 and Q8, with point D at its midpoint. Point D is connected to ends a1 and a2 of the magnetic winding assembly. The second arm includes Q9 and Q8. 10 The midpoint of the bridge arm is point E, which is connected to the b1 and b2 ends of the magnetic winding assembly.

[0042] Take ends a1 and a2 of the magnetic ring as end A; take ends b1 and b2 of the magnetic ring as end B; take end A as the positive voltage reference terminal of the magnetic ring, and its voltage is V. A Terminal B of the magnetic ring serves as the negative voltage reference terminal for the magnetic ring, and its voltage is V. B .

[0043] The motor controller outputs four PWM signals: PWM7, PWM8, PWM9, and PWM1. 10 These correspond to the four power switching transistors Q7, Q8, Q9, and Q1 connected to the power compensation circuit, respectively. 10 Through four power switching transistors Q7, Q8, Q9, Q... 10 The timing control, combined with the power supply configuration of V1=2V2=U / 3, enables V A V B A specific combination of potentials is generated, which ultimately synthesizes a four-level stepped waveform containing ±U / 2 and ±U / 6, i.e., an inverted voltage V, across the common-mode transformer. inject .

[0044] Want to cancel V b1 The carrier period T of the four PWM control signals output by the motor controller must be synchronized with the bearing voltage V. b1The PWM cycle is strictly synchronized; the voltage signal synthesized across the common-mode transformer is V. inject It should be a four-level stepped wave shape, with amplitude and V. b1 They are the same but opposite in phase.

[0045] The motor controller uses an independent master controller.

[0046] This invention also proposes a suppression method based on the aforementioned topology, the suppression method comprising four operating modes: in the first operating mode, corresponding to times t0~t1 and t7~t8, Q7, Q 10 With the circuit open and all others closed, the output at point D of the first bridge arm is +U / 3, which is applied to terminal A of the magnetic ring. The output at point E of the second bridge arm is -U / 6, which is applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage V across the magnetic ring is... AB =V A -V B =(+U / 3)-(-U / 6)=+U / 2, forming the first level; In the second operating mode, corresponding to times t1~t2 and t6~t7, Q7 and Q9 are turned on, and the others are turned off. Point D of the first bridge arm outputs +U / 3, which is applied to terminal A of the magnetic ring, and point E of the second bridge arm outputs +U / 6, which is applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage across the magnetic ring is +U / 6, forming the second level; In the third operating mode, corresponding to times t2~t3 and t5~t6, Q8 and Q9 are turned on, and the voltage across the magnetic ring is +U / 6, forming the second level. 10 When Q8 and Q9 are on and the others are off, the output of point D on the first bridge arm is -U / 3, which is applied to terminal A of the magnetic ring. The output of point E on the second bridge arm is -U / 6, which is applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage across the magnetic ring is -U / 6, forming the third level. In the fourth operating mode, corresponding to times t3 to t5, Q8 and Q9 are on and the others are off. The output of point D on the first bridge arm is -U / 3, which is applied to terminal A of the magnetic ring. The output of point E on the second bridge arm is +U / 6, which is applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage across the magnetic ring is -U / 2, forming the fourth level. Table 1 shows the proposed circuit topology for suppressing electro-corrosion of electric vehicle motor bearings under the four operating modes, with Q7 to Q9 connected. 10 The on / off state.

[0047] Table 1

[0048]

[0049] The above provides a detailed description of the non-contact active elimination topology structure and suppression method for the bearing voltage of a new energy vehicle motor proposed in this invention. Specific examples have been used to illustrate the principle and implementation of this invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A non-contact active voltage elimination topology for motor bearings in new energy vehicles, characterized in that, The topology includes a motor controller, a common-mode transformer, and a power compensation circuit; the motor controller is connected to the power compensation circuit, and the power compensation circuit is connected to the common-mode transformer; the topology injects a reverse voltage into the bearing voltage coupling path inside the motor through the common-mode transformer. V inject Eliminate bearing voltage V b The reverse voltage V inject With bearing voltage V b All are four-level stepped wave voltages, inverted voltages. V inject Levels of each step and bearing voltage V b The corresponding step levels have equal amplitudes, opposite polarities, and the same duration; the common-mode transformer uses the motor shaft as a single-turn winding on the secondary side, and there is no mechanical contact between the common-mode transformer and the motor shaft; The power compensation circuit includes four power switching transistors. Q 7. Q 8. Q 9. Q 10 It has four independent DC power supplies and two independent DC buses, referred to as the first DC bus and the second DC bus, respectively. The power switching transistors... Q 7 and Q The 8 series-connected transistors are then bridging the two ends of the first DC bus. Q 9 and Q 10 After being connected in series, it is bridging the two ends of the second DC bus; Two identical DC power supplies are connected in series at both ends of the first DC bus, and the voltage of the DC power supply is denoted as... V 1. Two identical DC power supplies are connected in series at both ends of the second DC bus, and the voltage of the DC power supply is denoted as... V 2, and numerically... V 1=2 V 2= U / 3, of which U Bearing voltage V b The amplitude; The common-mode transformer includes a magnetic winding assembly on the motor shaft. CMT 1 and CMT 2. Magnetic winding assembly CMT 1 includes a 1 end and b 1 end, magnetic winding assembly CMT 2 includes a 2 ends and b Two ends, in which the two magnetic winding groups are connected in parallel; The four power switching transistors Q 7. Q 8. Q 9. Q 10 It consists of two bridge arms, the first bridge arm includes Q 7, Q 8. The midpoint of the bridge arm is point D. Point D is adjacent to the magnetic winding assembly. a 1, a The two ends are connected; the second bridge arm includes Q 9, Q 10 The midpoint of the bridge arm is point E, and point E is the midpoint of the magnetic winding assembly. b 1, b Connect the two ends; magnetic surround group a 1, a End 2 serves as end A of the magnetic ring; the magnetic ring is then enclosed. b 1, b Terminal 2 is used as terminal B of the magnetic ring; terminal A of the magnetic ring is taken as the positive voltage reference terminal of the magnetic ring, and its voltage is... V A Terminal B of the magnetic ring serves as the negative voltage reference terminal for the magnetic ring, and its voltage is... V B .

2. The topology according to claim 1, characterized in that, Motor controller output four channels PWM Signal PWM 7. PWM 8. PWM 9. PWM 10 The four power switching transistors are respectively connected to the power compensation circuit. Q 7. Q 8. Q 9. Q 10 Through four power switching transistors Q 7. Q 8. Q 9. Q 10 Timing control, in conjunction with V 1=2 V 2= U The power configuration of / 3 enables V A , V B The corresponding potential combinations are generated, and finally synthesized at both ends of the common-mode transformer, including ± U / 2 and ± U The four-level stepped waveform of / 6 is the inverted voltage. V inject .

3. The topology according to claim 2, characterized in that, The four output channels of the motor controller PWM control signals PWM 7. PWM 8. PWM 9. PWM 10 The carrier period is the same as the PWM carrier period output by the motor controller to the drive circuit.

4. A method for suppressing topology structures based on any one of claims 1-3, characterized in that, The suppression method includes four operating modes: in the first operating mode, corresponding to... t 0~ t 1. t 7~ t At 8 o'clock, at this time Q 7, Q 10 Open, others off, first bridge arm D Point output + U / 3, add to end A of the magnetic ring, the second bridge arm E Point output - U / 6, Add to the magnetic ring B At the terminals, according to the principle of voltage superposition, the voltage across the magnetic ring is... V AB = V A - V B =(+ U / 3)-(- U / 6)=+ U / 2, forming the first level; In the second working mode, corresponding t 1~ t 2. t 6~ t At 7 o'clock, at this time Q 7, Q 9 is open, others are closed, first bridge arm D Point output + U / 3, added to end A of the magnetic ring, output + at point E of the second bridge arm. U / 6, applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage across the magnetic ring is now + U / 6, forming the second level; in the third working mode, corresponding to t 2~ t 3. t 5~ t At 6 o'clock, at this time Q 8, Q 10 Open, others off, first bridge arm D Point output - U / 3, added to end A of the magnetic ring, output at point E of the second bridge arm - U / 6, applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage across the magnetic ring is now - U / 6, forming the third level; in the fourth working mode, corresponding to t 3~ t At 5 o'clock, at this time Q 8, Q 9 is open, others are closed, first bridge arm D Point output - U / 3, add to end A of the magnetic ring, the second bridge arm E Point output + U / 6, applied to terminal B of the magnetic ring. According to the principle of voltage superposition, the voltage across the magnetic ring is now - U / 2, forming the fourth level.

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