Introduction
As we said in the latest article "Slip Rings in New Energy: Applications, Benefits and Future Trends", slip rings are used in new energy field. That includes the hydroelectric power stations on rivers, solar photovoltaic panels, new energy vehicles, etc.
Among them, the use of wind turbines is particularly common. When its blades rotate to collect the kinetic energy of the wind, wind turbine slip rings convert this energy into usable electrical energy and transmit it to the power grid. Without them, the complex mechanical components inside the turbine will not be able to operate stably. Today, let's learn about the specific application of slip rings in wind turbines!
How Do Slip Rings Work on Wind Turbines?
(1). Working principle of slip rings
During the operation of wind turbines, the blades, nacelles and other parts are in a state of continuous rotation, while many of the electrical systems and control systems connected to them are fixed.
Slip rings are mainly composed of stators and rotors, with brushes and conductive rings respectively. They are connected to the fixed structure of the turbine (tower or nacelle fixing place) and the rotating part (generator rotor shaft). Through the continuous contact between the brushes and the conductive rings, the slip rings transmit power, signals and data. Finally, they transmit power to the converter and other equipment at the bottom of the tower for subsequent processing and grid connection.
(2). Different Signals They Transmit
Generator
● Speed signal: The speed of modern large wind turbines can be as low as 5-10 rpm at low wind speeds and around 15-20 rpm near rated wind speeds. When the wind speed increases and the generator speed rises too fast, the control system adjusts the blade pitch angle and the electromagnetic torque of the generator according to the speed signal transmitted by the wind generator slip ring, so that its windward area is reduced, thereby reducing the speed.
● Temperature signal: During the operation of the generator, the normal operating temperature range is generally between 60-120℃. However, when the current passes through the winding, heat is generated, causing the internal temperature of the motor to gradually increase. The slip ring can transmit the temperature signal collected by the temperature sensor inside the generator. Once the control system receives the high temperature signal, it will start the cooling system, increase the speed of the cooling fan or adjust the flow of the cooling medium.
Variable Pitch System
● Pitch angle position signal: The main function of the variable pitch system is to adjust the pitch angle of the blade to adapt to different wind speeds. In this process, the slip ring transmits the pitch angle position signal of the blade and maintains an accuracy of about ±0.1°. The control system determines the current angle state of the blade according to the pitch angle position signal transmitted by the slip ring, and then issues instructions to drive the pitch motor to adjust.
● Pitch motor control signal: The pitch motor receives the control signal from the control system to drive the pitch action of the blade. These control signals are transmitted through the slip ring, and their signal frequency is generally between 500-1500Hz. The control signal includes the start and stop signal of the motor, the speed adjustment signal, etc.
Yaw system
● Wind direction signal: The task of the yaw system is to align the nacelle of the wind turbine with the wind direction and capture as much wind energy as possible. The wind direction sensor is installed on the top of the nacelle, and the measured wind direction signal is transmitted to the control system through the slip ring with an accuracy of ±5°. The control system calculates the deviation angle between the nacelle and the wind direction according to the wind direction signal transmitted by the slip ring, and then drives the yaw motor to adjust the direction of the nacelle.
● Yaw motor control signal: The operation of the yaw motor also depends on the control signal transmitted by the slip ring. Its control signal includes information such as start, stop, steering and speed control. When the wind direction changes, the control system sends a control signal through the slip ring, causing the motor to drive the nacelle to rotate in a more appropriate direction and speed.
Environmental Tests on Wind Turbine Slip Ring
(1). Common Environmental Challenges
Climate Factors
● Temperature: Wind turbines often work in outdoor environments and experience temperature changes during the day and night and seasons. In cold weather, the materials of various components of the slip ring may shrink, causing the contact pressure between the brush and the conductive ring to change. The increase in temperature will accelerate the aging of the slip ring materials, especially the insulating materials.
● Humidity and precipitation: When the humidity reaches saturation or even condensation occurs, water will form a conductive path on the surface of the slip ring. In wind farms at sea or in coastal areas, the air contains a lot of salt, which adheres to the slip ring with rain or fog, accelerating the corrosion of metal parts (housing, conductive ring, etc.).
● Dust and particulate matter: These tiny particles will enter the slip ring and continuously wear the surface of the brush and conductive ring like sandpaper. This will increase the contact resistance and generate electric sparks, which will not only affect transmission but also cause local overheating.
Mechanical Factors
● Vibration and impact: When the turbine blades encounter strong winds, the vibration amplitude will increase. This vibration will be transmitted to the slip ring, causing relative displacement and intermittent poor contact between the brush and the conductive ring.
● Rotational speed change: The slip ring needs to work stably at different speeds, such as from 100 to 5000 revolutions per minute. At high speeds, the friction between the brush and the conductive ring will increase. Centrifugal force may also cause the brush of the slip ring to wear more and the conductive ring to deform.
Electromagnetic Factors
● Electromagnetic interference: There are a large number of electrical equipment and lines inside the wind turbine, such as generators, inverters, etc. These devices will generate electromagnetic fields during operation. They will change the frequency and amplitude of the signal, causing the control system to receive wrong information and guide wrong instructions.
(2). How Can We Avoid Them?
● Material selection: For the brushes of the slip ring, precious metals, alloys, etc. are used. The conductive ring material can be plated with copper (gold, silver). For the shell and insulation materials, stainless steel, aluminum alloy, PTFE, POM, etc. are common choices. These materials have high conductivity, chemical stability and insulation, which can improve the transmission efficiency when used.
● Overall sealing structure: We can install fluororubber rings between the outer shell and shaft of the slip ring, at the interface and gap. At the same time, the internal channel of the slip ring is highly closed through the labyrinth sealing structure. This can prevent dust, moisture, etc. from entering the channel.
● Strengthen anti-seismic design: In the structural design of the slip ring, reasonable installation brackets and shock-absorbing materials can buffer its impact during operation. Alternatively, the components inside the slip ring can be connected by screw fastening and snap fastening.
● Optimize the contacts: The elastic brush bracket can automatically adjust the pressure of the brush according to the speed and working environment of the slip ring. In addition, the arc contact surface design can also reduce contact resistance, heat generation and wear.
● Heat sink design: We can design a large-area, multi-layer heat sink structure on the outer shell of the slip ring to improve the heat dissipation efficiency by increasing the heat dissipation area. Because they can quickly dissipate the heat generated during the working process to the surrounding air.
● Heat dissipation channel: In addition to the heat sink, a heat dissipation channel can also be designed inside the slip ring. This uses natural convection or forced convection to make the cooling air or cooling liquid flow in the channel to take away the heat.
Parameter Range of Wind Turbine Slip Ring
Different turbines have very different requirements in terms of power, speed, installation space, etc. It is difficult for a slip ring to meet all standards. Our standard through-hole slip rings such as BTH2586 or BTH3899 are suitable for some common wind turbine applications. And for specific functions, ByTune can provide some customized options for slip rings according to your wind turbine system requirements. These include:
• Size: outer diameter/length/with or without inner hole (with inner hole for easy through-shaft installation)
• With or without housing (housing protects internal components/without housing for easy heat dissipation)
• Number of channels
• Power or signal size of each channel
• Mounting interface (standard flange/special flange, etc.)
• Wire gauge and wire length (22AWG/300 mm or specified)
• Working environment: temperature (generally from -40℃ to +80℃)/speed (generally 500rpm/IP level (if it is a closed model, IP54-IP68)
FAQ
Q: What is the power transmission efficiency of your slip rings at rated power? Is it guaranteed?
A: Our slip rings can achieve power transmission efficiency of more than 95-98% at rated power. They have passed international quality certifications such as CE, UL, FCC, ISO, SGS, etc. In addition, we have professional testing equipment and laboratories, and detailed product test data reports can be attached to the order.
Q: For signal transmission, what is the transmission accuracy of your slip rings?
A: For various signal transmissions, our slip ring transmission accuracy can reach ±0.01%, especially in complex electromagnetic environments. We also use high-quality shielding materials and optimized signal transmission line design to reduce the impact of electromagnetic interference on signals.
Q: Does the insulation of the slip ring meet the relevant industry electrical safety standards?
A: You can rest assured that the maximum voltage peak that our slip rings can withstand is 10kV, which is fully in line with industry electrical safety standards such as IEC. We control the quality of insulation materials at every step of the production process.
Q: Can slip rings with specific signal transmission protocols be customized according to our control system requirements?
A: Yes. We customize slip rings with specific signal transmission protocols (such as CAN bus protocol) and frequency ranges (such as 1 - 10kHz) according to your control system requirements. Our professional technical team is able to develop an adaptive signal transmission module and integrate it into the slip ring design. The customization cycle is generally 4 - 6 weeks, during which technical solution discussions and design reviews will be provided.
Q: What is the expected service life of the slip ring?
A: Our slip rings are expected to have a service life of up to 10-15 years. Under normal use conditions, the mean time between failures (MTBF) can reach 50,000 hours. This is based on our strict raw material screening, production process and quality inspection system.
Q: What is your slip ring production process and quality control process?
A: We use advanced automated production processes, and have strict process standards and operating specifications from component processing to assembly. For example, we conduct strict factory inspections on each batch of raw materials, including material composition analysis and physical performance testing. Finished products also need to pass electrical performance, environmental adaptability, reliability and other tests.
Q: What is the current order delivery cycle? What if we have urgent needs?
A: Normally, the order delivery cycle for standard slip rings is 2 weeks, and for custom slip rings it is 4-6 weeks. If you have urgent needs, we will arrange expedited production based on the order quantity and urgency.
Q: What is your production capacity? Can it meet our future large-scale procurement needs?
A: We have an 80,000 square foot factory, and the annual production capacity is 80-10 million. With the adjustment of production plans and the expansion of equipment, we are confident that we can meet your large-scale procurement needs.
Q: Do you provide installation guidance and commissioning services?
A: Yes. We provide comprehensive after-sales services, including free online installation guidance and commissioning services. During the warranty period, we will regularly visit customers to understand the use of slip rings and provide free maintenance training. The warranty period is 2 years. During the warranty period, we will repair or replace any failure caused by non-human factors free of charge.
Conclusion
We believe that through today's article, you have learned more about wind turbine slip rings. For example, you know that they are responsible for electrical connections during the continuous rotation of the turbine and transmit signals between the generator, variable pitch system, and yaw system.
And during use, these slip rings are also subject to various moisture, dust, and vibration environments. But we can solve these problems through sealing structures, precious metal materials, and customized slip ring designs. If you want to customize slip rings for your wind turbine, please click "here", and more useful information can be acquired.