An electromagnetic damping generator for oil drilling downhole

Abstract

The present invention discloses an electromagnetic damping generator for oil drilling downhole, comprising a turbine, a permanent magnet generator portion, and an electromagnetic damper portion. The electromagnetic damper portion comprises an electromagnetic damper rotor, an excitation coil, a bearing seat, and a retaining ring for a hole. The electromagnetic damper rotor is fixed to the rotating shaft, and the excitation coil is fixed to the bearing seat via two left and right holes using retaining rings. The bearing seat is made of a magnetically conductive material and can act as an electromagnetic damper stator and rotate within the generator housing. The excitation coil current comes from a power supply after full-wave rectification of a three-phase permanent magnet generator. The permanent magnet motor winding is wound on the permanent magnet motor stator, and the permanent magnet motor stator is axially fixed via the bearing seat and the bearing seat. The present invention can reduce the current in the electromagnetic damper excitation coil when the rotating shaft rotates too low, thereby increasing the rotating shaft rotate speed. This ensures that the output power and output voltage of the generator are relatively stable, meeting operating requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors and relates to an electromagnetic damping generator for oil drilling downhole, comprising a turbine, a permanent magnet generator and an electromagnetic damper. The damper regulates the speed of the permanent magnet generator to ensure the stability of the output power and voltage of the permanent magnet generator, thereby preventing the generated voltage from being too high and damaging electrical equipment. Technical Background

[0002] To rapidly convert and utilize unstable energy, generators that rely on unstable fluids such as mud, water, or wind as their prime movers experience unstable output voltage. For example, the trend in modern drilling is toward intelligent drilling. Downhole intelligent tools are evolving from simple data measurement and signal transmission to integrated measurement, control, and transmission, resulting in an ever-increasing demand for current. Downhole turbine generators powered by flowing mud can effectively address the power requirements of these intelligent instruments. However, they suffer from unstable mud flow rates and dynamically changing power loads, leading to unstable generator voltage. Conventional voltage stabilization technologies struggle to adapt to downhole operating conditions under high power conditions, making it easy for intelligent tools to overload and burn out. This severely impacts drilling efficiency and incurs significant costs during equipment maintenance. Summary of the Invention

[0003] The present invention overcomes the shortcomings of existing downhole turbine generators and designs an downhole electromagnetic damping generator for oil drilling based on the eddy current braking principle and the generator principle, which can prevent the generator output voltage from being too high or the power from being insufficient; and the generator structure is relatively simple and easy to control.

[0004] The present invention is achieved through the following solutions:

[0005] An electromagnetic damping generator for oil drilling downhole, comprising: a turbine, a permanent magnet generator part and an electromagnetic damper part; wherein,

[0006] The electromagnetic damper comprises an electromagnetic damper rotor 17, an excitation coil 16, a bearing seat (right) 15, and a retaining ring 14 for the holes. The electromagnetic damper rotor 17 is a toothed rotating disk with four (or more) salient poles on one side and an L-shaped axial cross-section. The damper stator is replaced by the bearing seat (right) 15, which is made of magnetically conductive material and can rotate within the generator housing 6. The electromagnetic damper rotor 17 is fixed to the rotating shaft 2. The excitation coil 16 is secured to the bearing seat (right) 15 via retaining rings 14 through two holes on the left and right. The excitation coil 16 draws its current from the full-wave rectified power supply of the three-phase permanent magnet generator. Its current is regulated by the CPU using PWM control according to the PID control principle based on the generator output voltage (which varies proportionally with the generator speed). The left side of the electromagnetic damper rotor 17 is axially fixed by a deep groove ball bearing 8, and the right side is axially fixed by a round nut retaining washer 19 and a stop nut 18. Shock-absorbing pads 10 are provided between the outer rings of the bearings on both sides and the bearing seats for buffering and shock absorption.

[0007] The permanent magnet generator (PMG) is a conventional three-phase PMG structure, comprising a three-phase PMG stator 13, a rotating shaft 2, PMG windings 11, and permanent magnets 12. The permanent magnets 12 are embedded in grooves on the rotating shaft 2 and are evenly distributed along the circumference. The PMG windings 11 are wound around the three-phase PMG stator 13, which is axially secured by bearing blocks (left) 7 and (right) 15. Bearings 8 and 9 are used between the bearing blocks (left) 7 and (right) 15 and the rotating shaft 2 for support and rotation.

[0008] The permanent magnet generator part and the electromagnetic damper part are immersed in lubricating oil for operation. The anti-rotation support housing 4, the generator housing 6 and the breathing joint 22 separate the permanent magnet generator part and the electromagnetic damper part from the outside world through the O-ring 5.

[0009] The rotating shaft 2 of the permanent magnet generator is made of 17-4ph stainless steel, and the stator 13 of the three-phase permanent magnet motor is made of silicon steel sheets.

[0010] A gap of approximately 1 mm is maintained between the outer circumference of the salient poles of the electromagnetic damper rotor 17 and the inner wall of the bearing seat (right) 15. A gap of approximately 1 mm is maintained between the permanent magnet generator rotor assembly and the inner circumference of the three-phase permanent magnet motor stator 13.

[0011] Mud or other fluids continuously flow through the outer surface of the generator housing 6, which serves as a power source and can also be used for cooling and heat dissipation.

[0012] When an electromagnetic damping generator for oil drilling downhole according to the present invention is working, fluids such as mud impact the turbine at the shaft end, driving the rotating shaft 2 to rotate. By controlling the current of the excitation coil 16 to change the braking torque provided by the electromagnetic damper, the speed of the generator rotating shaft 2 is adjusted to ensure that the output power and output voltage of the generator are relatively stable to meet working requirements.

[0013] A portion of the full-wave rectified current generated by the permanent magnet generator powers the electromagnetic damper excitation coil 16, generating an induced magnetic field around the excitation coil 16. This creates a closed magnetic circuit between the electromagnetic damper rotor 17, the air gap, and the bearing seat (right) 15. As the electromagnetic damper rotor 17 rotates synchronously with the rotating shaft 2, the bearing seat (right) 15 continuously cuts through the magnetic lines of force generated by the electromagnetic damper rotor 17, generating eddy currents within a certain depth of the bearing seat (right) 15. The eddy current field generated by these induced eddy currents interacts with the original magnetic field generated by the excitation coil 16, generating a braking torque that hinders the rotation of the electromagnetic damper rotor 17, thereby regulating the speed of the permanent magnet generator rotor assembly. Adjusting the current in the excitation coil can alter the braking power of the electromagnetic damper. The eddy currents act on the bearing seat (right) 15, generating heat that is conducted to the generator housing 6. Fluids such as mud continuously flow across the outer surface of the generator housing 6, dissipating heat.

[0014] When braking is not required, the excitation current in the excitation coil 16 is cut off, and the electromagnetic damper rotor 17 will not generate magnetic lines of force, that is, no braking torque effect will be generated.

[0015] The main advantages of the electromagnetic damping generator for oil drilling downhole of the present invention are as follows:

[0016] The electromagnetic damper of the present invention maintains a 50% maximum braking torque during normal generator operation. When the generator speed is too high, the electromagnetic damper's braking power is increased to suppress it, reducing the speed of the rotating shaft 2 and preventing damage to the generator components caused by overload. When the rotating shaft speed is too low, the electromagnetic damper's braking power is reduced, increasing the speed of the rotating shaft 2 so that the generator's output power and output voltage meet operating requirements.

[0017] In the present invention, the sealing ring 5 on the left anti-rotation support shell 4 and the right breathing joint 22 seals the internal permanent magnet generator and the electromagnetic damper in a closed space, achieving complete isolation between fluids such as mud and the internal permanent magnet generator and the electromagnetic damper, preventing fluids such as mud from entering the interior and affecting the permanent magnet 12, stator assembly and excitation coil 16 of the permanent magnet generator, providing a stable environment for the electromagnetic damping generator in the oil drilling well, and improving the overall life.

[0018] In the present invention, the bearings inside the body are completely in lubricating oil, which provides good conditions for lubrication and cooling of the bearings. At the same time, the bearings are not in contact with fluids such as mud, thereby increasing the service life of the bearings and improving the service life of the generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1, a front view of an electromagnetic damping generator for oil drilling downhole according to the present invention;

[0020] Figure 2 , a partial cross-sectional view of the electromagnetic damper of an electromagnetic damping generator for oil drilling downhole according to the present invention.

[0021] Figure 3 , a control principle diagram of an electromagnetic damping generator for oil drilling downhole according to the present invention.

[0022] In the figure: 1. Turbine, 2. Rotating shaft, 3. Bushing, 4. Anti-rotation support housing, 5. Sealing ring, 6. Generator housing, 7. Bearing seat (left), 8. Deep groove ball bearing, 9. Tapered roller bearing, 10. Shock absorber pad, 11. Permanent magnet motor winding, 12. Permanent magnet, 13. Three-phase permanent magnet motor stator, 14. Retaining ring for hole, 15. Bearing seat (right), 16. Excitation coil, 17. Electromagnetic damper rotor, 18. Stop nut, 19. Round nut stop washer, 20. Bearing cover, 21. Wire locking nut, 22. Breathing connector. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. Figure 1 As shown, the left turbine 1 of the present embodiment is fixedly connected to the rotating shaft 2. The permanent magnet generator (PMG) is powered by a fluid such as mud impacting the turbine 1. The permanent magnets 12 of the PMG are embedded in grooves on the rotating shaft 2 and are evenly distributed along the circumference. The three-phase PMG stator 13 is secured by a bearing block (left) 7 and a bearing block (right) 15. These blocks, along with the rotating shaft 2, are supported and rotated using bearings 8 and 9. The PMG windings 11 are wound around the three-phase PMG stator 13. In the electromagnetic damper, the excitation coil 16 is secured to the bearing block (right) 15 via two holes on the left and right sides using a retaining ring 14. The current in the excitation coil 16 is derived from the full-wave rectified power supply of the three-phase PMG. Its current is controlled by the CPU using PWM (Pulse Width Modulation) according to the PID control principle, based on the generator output voltage (which varies proportionally with the generator speed). The braking torque is controlled by adjusting the current in the excitation coil 16. A gap of about 1 mm is maintained between the outer circle of the salient pole of the electromagnetic damper rotor 17 and the inner wall of the bearing seat (right) 15.

[0024] In the present invention, mud impacts the turbine, driving the rotating shaft 2 to rotate, thereby generating current in the permanent magnet generator. This current is then full-wave rectified and output to other electrical devices. A portion of this rectified current is then input into the electromagnetic damper excitation coil 16 by the CPU according to PID control principles through PWM regulation, thereby activating the electromagnetic damper. The turbine drives the rotating shaft 4, causing the power P1 generated by the permanent magnet generator and the braking power P2 generated by the electromagnetic damper to be calculated by an adder to obtain the adjusted permanent magnet generator power P. This allows the permanent magnet generator's output voltage and power to be controlled, maintaining a relatively stable output power and voltage range to meet operational requirements.

[0025] This downhole electromagnetic damping generator for oil drilling has two main operating modes. Mode 1: When the flow rate of a fluid, such as mud, is excessive, impacting turbine 1 and causing shaft 2 to rotate too fast, the permanent magnet generator may become overloaded. Increasing the current in the electromagnetic damper's excitation coil 16 can increase the electromagnetic damper's braking power, i.e., the braking torque on shaft 2, thereby reducing shaft 2's rotational speed and preventing the permanent magnet generator from overloading. Mode 2: When the flow rate of a fluid, such as mud, suddenly decreases, causing shaft 2's rotational speed to drop, the permanent magnet generator's output power and voltage may not meet operating requirements. In this case, since the electromagnetic damper initially operates at 50% of its maximum braking torque, reducing or cutting the excitation current in excitation coil 16 reduces the electromagnetic damper's braking power, increasing shaft 2's rotational speed and thereby increasing the permanent magnet generator's output power and voltage to meet operating requirements.

[0026] The fluid such as mud flows over the outer surface of the generator housing 6, which can take away the heat generated by the permanent magnet generator part and the electromagnetic damper part.

Claims

1. An electromagnetic damping generator for oil drilling, characterized by: It includes a turbine, a permanent magnet generator and an electromagnetic damper part; the electromagnetic damper part includes: an electromagnetic damper rotor, an excitation coil, a right bearing seat and a retaining ring for the hole; the electromagnetic damper rotor is a toothed turntable with multiple salient poles distributed on one side and an L-shaped axial section. The electromagnetic damper stator is replaced by a right bearing seat, which is made of magnetic conductive material and rotates in the generator housing; the electromagnetic damper rotor is fixed to the rotating shaft, and the excitation coil is fixed to the right bearing seat with a retaining ring through two left and right holes. The excitation coil current comes from the power supply after full-wave rectification of the three-phase permanent magnet generator. Its size is adjusted by the CPU according to the PID regulation law and PWM according to the change of the generator output voltage; the left side of the electromagnetic damper rotor is axially fixed by the bearing, and the right side is axially fixed by a round nut stop washer and a stop nut; and a shock-absorbing pad is provided between the outer ring of the bearing and the bearing seat on both sides; The permanent magnet generator consists of a three-phase permanent magnet motor stator, a rotating shaft, permanent magnet motor windings, and permanent magnets. The permanent magnets are embedded in the grooves of the rotating shaft and are evenly distributed along the circumference. The permanent magnet motor windings are wound around the three-phase permanent magnet motor stator, which is axially fixed by left and right bearing seats. Deep groove ball bearings and tapered roller bearings are used between the left and right bearing seats and the rotating shaft for support and rotation. The two bearings between the left bearing seat and the rotating shaft are fixed with a shaft shoulder and a sleeve. The mud impacts the turbine mud pump to drive the shaft to rotate, thereby causing the permanent magnet generator to generate current, which is then output to other electrical equipment through full-wave rectification. After a part of the current is rectified, the CPU uses PWM regulation according to the PID regulation law to input the current into the excitation coil of the electromagnetic damper, so that the electromagnetic damper starts working; the turbine drives the shaft to rotate, so that the power P1 generated by the permanent magnet generator and the braking power P2 generated by the electromagnetic damper are calculated by the adder to obtain the adjusted permanent magnet generator power P, thereby controlling the output voltage and power of the permanent magnet generator. Within a relatively stable range, the working requirements are met; when the mud flow is too large and impacts the turbine, causing the shaft to rotate too fast, the current in the electromagnetic damper excitation coil is controlled to increase, thereby increasing the braking power of the electromagnetic damper, that is, increasing the braking torque on the shaft to reduce the shaft speed; when the mud flow suddenly decreases, causing the shaft speed to decrease, since the electromagnetic damper is in a working state of 50% of the maximum braking torque when it starts working, reducing or cutting off the excitation current in the excitation coil will reduce the braking power of the electromagnetic damper and increase the shaft speed, thereby increasing the output power and output voltage of the permanent magnet generator.

2. The electromagnetic damping generator for oil drilling downhole according to claim 1, characterized in that: The rotating shaft of the permanent magnet generator is made of stainless steel, and the stator of the three-phase permanent magnet motor is made of silicon steel sheets.

3. The electromagnetic damping generator for oil drilling according to claim 1, characterized in that: The permanent magnet generator part and the electromagnetic damper part are immersed in lubricating oil for operation, and the anti-rotation support housing, the generator housing and the breathing joint separate the permanent magnet generator part and the electromagnetic damper part from the outside world through O-rings.

4. The electromagnetic damping generator for oil drilling downhole according to claim 1, characterized in that: A gap of 1mm is maintained between the outer circle of the electromagnetic damper rotor salient pole and the inner wall of the right bearing seat; a gap of 1mm is maintained between the permanent magnet generator rotor assembly and the inner circle of the three-phase permanent magnet motor stator.

5. The electromagnetic damping generator for oil drilling downhole according to claim 1, characterized in that: Mud continuously flows through the outer surface of the generator housing, serving as a power source while also being used for cooling and heat dissipation.

6. The electromagnetic damping generator for oil drilling downhole according to claim 1, characterized in that: After a part of the full-wave rectified current generated by the permanent magnet generator is used to power the electromagnetic damper excitation coil, an induced magnetic field is generated around the excitation coil, forming a closed magnetic circuit between the electromagnetic damper rotor, the air gap and the right bearing seat; when the electromagnetic damper rotor rotates synchronously with the rotating shaft, the right bearing seat continuously cuts the magnetic lines of force generated by the electromagnetic damper rotor, generating eddy currents in the right bearing seat. The eddy current field formed by the induced eddy current interacts with the original magnetic field generated by the excitation coil, thereby generating a braking torque to hinder the rotation of the electromagnetic damper rotor, thereby adjusting the speed of the permanent magnet generator rotor assembly.

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