Preformed Windings produces high-voltage coils and bars, driving innovation, excellence, and the global energy transition
Preformed Windings (Preformed) is a leading manufacturer of high-voltage coils and bars, operating from two state-of-the-art facilities near Sheffield, UK, with over 50 years of experience. Priding itself on delivering the best quality coils and bars for high-voltage motors and generators, Preformed is a trusted partner to the most respected quality-focused service companies globally.
Offering 24/7 service, Preformed is the preferred supplier across industries such as hydro, nuclear power, oil and gas and power generation. Its focus on quality and service drives the delivery of bespoke solutions using the latest technologies and materials. “We’ve been around since 1968,” begins James Stevens, CEO, “and at our core, we’re a pure product manufacturer. What we do is very specialized. We design and manufacture high-voltage bars and coils for motors and generators. 
Over the past few years, we’ve grown rapidly. In fact, in the last two years alone, we’ve doubled in size. We’re now a team of around 120 people, working across two manufacturing facilities, sitting side by side.
“Our expertise is in shaping and insulating copper. That’s really the heart of what we do, and we’ve invested heavily in staying at the forefront of that craft. Over the last five or six years, we’ve invested well over 30,000 hours of R&D to develop high-quality insulation systems aimed at extending the life of high-voltage machines, reducing maintenance, and delivering specific performance advantages such as ultra-low partial discharge levels, which is a key indicator of insulation health,” he elaborates.
“We export 98-to-99 percent of our products globally, mainly into sustainable power generation. A large portion goes into hydroelectric and nuclear applications around the world. We’re honored to be the supplier of choice for organizations like GE Vernova and Voith, among others, and to be trusted by end users ranging from the US Army Corps of Engineers to major nuclear operators.”
James goes on to share the company’s three core value propositions, believing service organizations and utilities deserve a supply chain that doesn’t compete with them. “This is why we focus purely on product manufacture, unlike many others in our sector,” he explains. “We integrate within the supply chain, so our customers’ success is our success. Alongside that, we’re service leaders: we offer 24/7 technical support and build multi-tier relationships to deliver a genuinely world-class level of service. Those three pillars: non-competing, high quality, and true partnership are what define us.”
At the end of Q4 2024, Preformed opened its second manufacturing facility, which increased capacity by around 60 percent. That expansion was entirely driven by market demand. “The new facility allows us to keep lead times aligned with customer expectations while meeting the growing volume requirements we’re seeing both from our partners and across the global market,” James shares. “We’re in the middle of what I’d call an electrification super-cycle, driven by rising power demand from AI, population growth, and industrialization. Our products fit directly into both the push for more power and the drive toward Net Zero. The expansion was the first step, and we’re already planning the next: moving to a single, much larger facility, roughly twice the size of our two current sites, to support the continued demand.
“Our mantra, and our whole identity really, is ‘obsessed with quality.’ It’s what our brand is built on,” James explains. “A strong reputation takes years to build and only moments to lose, and our customers think the same way. They’re proud of the quality they deliver, and they rely on us to help them uphold that.”
While Preformed has grown quickly, over the past two years, its non-conformance and scrap rates have fallen. Achieving that while doubling the workforce meant being extremely deliberate about how it approached expansion. “In our world,” he continues, “it takes six-to-nine months before a new team member is ready to handle customer product, so we front-load investment heavily. We accept that a new hire won’t deliver direct value immediately, because the alternative, which compromises quality, is far more costly in every sense.
“A big part of maintaining standards has been developing a robust training system. We focus not only on quantitative knowledge but also tacit knowledge, which comes only from experience. We’ve mapped the complexity of each production process, identified the true minimum competency levels, and built training paths that progress logically. People learn differently, so we’ve designed a system flexible enough to accommodate all styles. The result is a team we can sign off with genuine confidence, and a structured approach that ensures skills continue to grow and stay sharp.”
Automation
Automation is increasingly important for Preformed, as it is for all manufacturing firms, and the company’s approach is to bring in proven technologies that aren’t typically used in the industry, such as 3D scanning, 3D printing, and, increasingly, AI, and applying them in ways that genuinely add value. “For example, our new training system is AI-supported,” James elaborates. “We didn’t want a static library of modules; we wanted people to ask specific questions and receive tailored answers, matched to different learning styles.
“We also work closely with Sheffield Hallam University through our KTP associates, who have helped us integrate advanced CAD tools, 3D scanning and additive manufacturing capabilities. Beyond that, we’ve invested in smarter production scheduling. Off-the-shelf software doesn’t give a holistic view, so we’ve built a system that supports the whole business.” 
The industries Preformed serves are inherently involved in the sustainable energy transition, but the company perceives its role in supporting the development and maintenance of energy infrastructure more broadly.
“In our business, we don’t just provide a like-for-like replacement when motors and generators are modernized,” James continues. “We look at how we can use cutting-edge insulation systems and technology to not only replace what’s there but improve it, by extending the life, increasing efficiency, and even boosting generator output. It’s not unusual for our windings to raise output by ten-to-45 percent. With the average hydro generator in North America around 55 years old, there’s a massive opportunity to increase renewable energy output quickly and with minimal carbon footprint.
“At the same time, we’re focused on sustainability, reducing our Scope 1 and 2 emissions, and offsetting locally where our customers are, so by Q1 2026, we’ll be Scope 1 and 2 carbon neutral, with Scope 3 reductions following shortly after.”
Turning to the future, James shares his hopes for the business in the years to come: “We’re currently a £15 million business, and our plan is to triple in size over the next five years; a target I think is reasonably conservative given the market demand we’re seeing. Nuclear is back in focus, and the development of small modular reactors is taking off, creating real opportunities for high-quality windings. We’re also about to launch Preformed Windings Labs in Q1 next year; a facility for voltage endurance, thermal cycle, and PD assessment, simulating the life of windings. This will accelerate R&D and demonstrate that our products, for example in hydro dams, are expected to outlast the concrete itself. While there’s interest in expanding internationally, our immediate focus is on growing our UK operation and meeting current market demand.
“Because we’re purely focused on our product, we’re hungry to share knowledge and carry out R&D with the industry. Our call to action for utilities, consultants, and partners is simple: collaborate with us to develop products that meet the demands of today’s electrification stage. We work closely with organizations like the International Hydropower Association, for example, to share best practice and upskill the industry,” James concludes. “We’re committed to sharing knowledge freely and helping the industry specify products designed to last and perform at the cutting edge.”