28 n MOTORS May 2026 www.drivesncontrols.com Custom slipring motors give London waterworks a new lease of life Thames Water serves 16 million customers across London and the Thames Valley. The utility’s high-lift pump installation at its Coppermills Water Treatment Works had experienced repeated failures, due mainly to the age of its equipment. Because Thames Water is planning to build a new station in about 10 years’ time, it put out a tender for an economic drive system that would ensure that the existing pumps would continue to operate reliably until then. Some bidders proposed using variablespeed drives (VFDs), which would have required major reconstruction to accommodate the control systems and transformers, and would have been a costly exercise. The German large motors specialist Menzel Elektromotoren suggested an alternative – using slipring motors that would be compatible with the existing installation and would use the electric infrastructure and starting equipment already in place. Menzel Great Britain was awarded the contract to supply ten 3.3kV slipring motors, each weighing seven tonnes – its biggest project to date. The motors, with shaft heights of 500mm, are designed to mount vertically on top of the pumps. Six of the IP55-protected motors have air-to-water heat exchangers and four have air-to-air heat exchangers. Between then, they provide outputs of 746 or 343kW and have rated torques of 1.2075 or 5.551 kNm. Menzel has an expertise in building and customising large slipring motors. The 10 motors supplied to Thames Water are using the site’s existing pump pedestals, reducing work and minimising disruption. Menzel tailored the terminal boxes to match the existing installation to make the cabling as easy and cost-efficient as possible. The design also anticipates future extreme summer temperatures. The new motors have a 5% higher efficiency than the original motors, and are easier to maintain. They have an expected lifespan of at least 25 years. The motor engineers worked closely with Thames Water’s contractor, MWH Treatment. The project came in under budget and was completed on schedule. Compared to the proposed VSD-based alternatives, the slipring motors have saved Thames Water hundreds of thousands of pounds, and took much less time to install n Ten slipring motors, each weighing seven tonnes, have extended the lifespan of a key water treatment plant in London, securing the water supply until a new plant is built in about ten years’time. The slipring motors were custom-built to mount on top of existing pumps at the Thames Water treatment works
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