Helix is a Milton Keynes-based designer and manufacturer of high-performance electric motors, high-voltage inverters and electric drive units.
It said the deal would help it invest in product development, increase production and expand into new markets, including North America.
"With MiddleGround’s operational expertise and guidance, we are confident in our ability to grow and reach a wider range of clients at a greater scale," said Darren Cairns, Helix director and CEO.
MiddleGround Capital specialises in B2B industrial businesses and has invested in companies like Xtrac, New Eagle and Race Winning Brands.
John Stewart, its founding partner, said: "Helix is well positioned to scale its product offerings and expand its market, capitalizing on the shift toward electric vehicles. We are eager to support their talented team in reaching their next stage of growth."
The group added that it aimed to enhance Helix’s commercial strategy, build production capacity, implement procurement best practices, invest in new product development and expand into new markets.
All content produced by The Business Magazine’s expert journalists will now be featured in Insider’s market-leading business magazines and on the Insider Media website.
This means even more in-depth business news, exclusive insights and unrivalled coverage of key regional deals - all brought to you by the UK’s leading regional business news platform.
Stay ahead of the competition with the stories that matter most to you.
