By Nitin Kulkarni
Smart Application Engineering by detailed understanding of the operating conditions and function of the product is needed for many industries. It is especially critical for Wind Industry due to accessibility challenges up tower compared to typical industrial applications on the ground. But there are enough warning signs in most cases before the catastrophic failures or flashovers. Too often, these signs are either not understood or underestimated. Wind turbine generators are high-voltage machines; design or manufacturing faults and use of cheap products are common root causes of electrical failures. These products are not commodity. After install, the lack of preventive maintenance could result in severe damage, costly repairs, and unexpected shutdown of the wind turbine, all of which can be significantly minimized by applying better product and timely service by wind farm technicians.
The growth in wind as a major source of power is closely related to improved reliability of wind turbines. The rotation of the blades and shaft must include wear of the interacting parts and thereby concerns for maintenance and life of the related components. The wind turbine includes a wide variety of sliding electrical contacts to conduct electric power to and from the rotating parts. Along with generators and motors, some other systems also include grounding and lightning protection. Majority of these electrical systems include the sliding contact, commonly called a carbon brush, the brush holders with spring, and the rotating collector rings. The wear at the sliding contact interface can be a limiting factor with reduced reliability, and more frequent high-cost maintenance cycles.
A carbon brush is subject to wear from both friction and from electrical erosion. The objective is to attain a balance between these factors for a minimal total wear rate of the interacting sliding surfaces. Optimal designs and appropriate preventive maintenance service can offer impressive results with minimal planned downtime and reduced operating costs, but it takes some effort.
Following are significant elements for continually improving the function of the carbon brushes in a wind turbine.
There is always an opportunity for improvement by first understanding the symptoms and then fixing it. Predictive and preventive maintenance is the KEY to success. Show your used carbon brushes, springs, and holders to subject matter experts to learn the warning symptoms. With many turbines going out of warranty, look for improvement for life expectancy and reduction in long term maintenance cost. Be flexible for engineering trials with constant monitoring. With information on the existing design, data on the operating conditions, and observation of trends toward undesirable symptoms, adjustments in the sliding electrical contact system can attain excellent results. (image 6) The reward for satisfactory wind generator operation is significant and it is certainly worth the time investment!
Nitin Kulkarni is Vice President Engineering and Business Development at Helwig Carbon Products, a family-owned, American manufacturer which specializes in carbon brushes, brush holders, spring assemblies, metal graphite brushes, and carbon graphite components.