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FEATURE GEARS & GEARBOXES For companies in the renewable energy space,


advanced motor systems such as those operating on magnetic gears can be instrumental in


delivering efficiency, reliability and cost-effective operation. Gary Rodgers, CEO of Magnomatics, answers key questions about the practical benefits of magnetic gear technology in the ocean and wind renewable energy sectors


Energy efficiency is becoming ever more important for businesses, especially in times of increased energy costs. How important is system efficiency to manufacturers and what benefits does this efficiency bring? Efficient systems are those which achieve maximum output with the minimum of energy going to waste. Old-fashioned incandescent light bulbs are a typical example of an inefficient system because 80% of their energy was turned into heat, not light. As such, they wasted significant amounts of energy and were expensive to run. In the field of motor systems, traditional motors have the same issue. In electrical machines, energy is wasted


due to the heat generated within the motor windings and core through friction in seals and bearings. Large, direct-drive electric generators used in wind turbine and ocean energy applications are constrained to operate at the speed of the turbine blades, so it can be difficult to achieve a high efficiency due to the relatively high torque and low speed.


Improving system efficiency brings important benefits to operators and the environment, including the reduction of operational costs throughout the system’s lifespan. Given the high costs of energy today, such savings can be considerable. As 33% of National Grid energy is still being generated by fossil fuels (32% gas, 1% coal), energy-efficient systems powered by


the grid can help reduce CO2 emissions. Compared with traditional systems, magnetically geared generators are significantly more efficient. With a design that uses magnets to transmit torque between the input and output shafts of the gear, these systems do not require mechanical contact, as with a traditional mechanical gearbox. As a consequence, energy is not wasted through friction and pumping of lubricants. Efficiency is further increased because these generators run at a higher speed than the input shaft by virtue of the integrated magnetic gear. This reduces the load and the resulting energy wasted as heat in the coils is significantly reduced, in turn leading to lower


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operating temperatures. Reduced operating temperatures lead to higher reliability. They also benefit from reduced noise and vibration compared to mechanically geared generators. Together, these features help operators to cut energy costs, reduce their carbon footprint and overcome operational bottlenecks.


What are the key factors that need to be considered when choosing a magnetic gear solution in the renewables space? Turbine gearboxes have become key technologies in the global renewable energy sector and are critical components in both wind and ocean generation systems. Given the heavy demands on these systems and their operational locations, energy efficiency and reliability are vital factors when considering which generator system to use. Aside from the energy efficiency benefits mentioned above, magnetically geared motors are also extremely reliable. Designed to overcome the torque limitations of conventional generator systems through magnetic gearing, they can be 33% smaller and lighter than an equivalent permanent magnet motor, and less than half the size of an induction motor. These lightweight generators have a knock-on effect on the structural requirements for the tower, significantly reducing the cost per MW installed. Indeed, even with this compact size, their design can make them 2% to 3% more efficient without torque density being affected. Additionally, besides bringing great efficiency, the gears’ ability to operate with low load, low currents and at low operating temperatures extends their lifespan. Importantly, as mechanical contact is not required, these gears do not suffer from wear. With all these factors considered, magnetic motors are highly efficient and reliable systems


48 DESIGN SOLUTIONS JUNE 2024


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