Every transformer humming on a pole, every substation feeding a city, every locomotive pulling a train has the same hidden heart: coils of copper, wound with extraordinary precision, carrying current without wasting it as heat. It is one of the most unglamorous jobs in the power industry — and one of the most exacting. In Thane, Maharashtra, a company that has been perfecting it for over three decades is now winding conductors for some of the biggest names in global power equipment. That company is Rational Engineers Limited.
Copper winding conductors at Rational Engineers’ facility. (Image: Rational Engineers)
The conductor that carries the grid
Rational Engineers’ signature product is the continuously transposed conductor, or CTC — a bundle of enamelled rectangular copper strips, transposed in parallel and wrapped in pure cellulose paper tapes, that forms the winding inside a power transformer. The transposition is the clever part: by constantly swapping the position of each strand along the length of the conductor, CTC evens out current distribution and cuts the eddy-current losses that would otherwise heat a transformer from the inside. It is the difference between a transformer that merely works and one that runs efficiently for decades.
Around that flagship, the company has built a catalogue of twelve conductor families. Paper-insulated copper conductors (PICC) to IEC, IS, DIN and BS specifications. Enamelled copper and aluminium magnet wire in round and rectangular sections. Mica-insulated conductors for high-voltage rotating machines and inverter-driven motors. Kapton-insulated copper that resists corona discharge at high temperatures. Fibreglass-covered conductors impregnated with Class F and Class H varnish. High-frequency litz wires that minimise skin and proximity-effect losses — the kind of conductor that goes into EV battery charging equipment. And precision bare and tin-coated copper busbars, machined and finished to order.
The range is deliberately wide because the applications are. The company’s conductors go into power transformers and distribution transformers, into HT and LT motors, into locomotives and traction systems, into on-load tap changers, switchgear and busbar systems, and into earthing cables. Wherever electricity has to be carried, switched or transformed, there is a Rational conductor designed for the job.
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Three plants, 38,000 tonnes a year
Scale is what turns a good conductor maker into a supplier the world’s transformer giants can rely on. Rational Engineers runs three manufacturing locations — at Wada, Daman and Vadodara — with a combined annual capacity of 38,000 metric tonnes of copper and aluminium winding conductors. The company says its copper is electrolytic grade at 99.97% purity, sourced from verified suppliers, and every order passes multi-stage quality checks: incoming, in-process and final.
Power transformers in a substation yard — the machines Rational Engineers’ conductors are wound into. (Image: Rational Engineers)
That discipline shows up in the numbers the company reports: 98% on-time delivery across all orders, and a team of more than 350 skilled people across its plants and Thane headquarters. The company’s manufacturing and quality control is certified to ISO 9001:2015, and its operations run on a simple principle the company states plainly — copper and aluminium are infinitely recyclable, and the business is managed around resource efficiency and continuous reduction of energy and water intensity.
From Thane to the world
The customer list reads like a roll call of the power industry. Rational Engineers supplies Siemens, Toshiba, TBEA, Crompton, BHEL, CG Power & Industrial Solutions, Voltamp, Schneider, GE Vernova, Hitachi, Alfanar and T&R Transformers and Rectifiers — more than 350 customers in all, across 25 countries and four continents. One leading power transformer maker has called the company its preferred copper conductor supplier for over a decade.
The company has built its own bridge to those markets. Its international trade and distribution arm, REL Metals Trading LLC in the UAE, serves the Middle East, Africa and emerging markets, putting Rational’s conductors into grids far beyond India’s borders. It is a quiet kind of export story: not a finished consumer product with a brand on the box, but the precision-engineered material inside the machines that keep the lights on.
A family business that scaled
Rational Engineers was founded in 1989, and its modern chapter began in 2006, when Mahendra Jain — a mechanical engineer — took over the company with a vision of transforming how copper conductors are produced and distributed in India. His son Jubin Jain, an electrical engineer, joined in 2018, bringing the next generation into a business that has now been manufacturing continuously for over three decades.
The growth has accelerated sharply. Company filings show revenue of ₹1,413 crore in FY26, up 58% on the previous year — a surge that reflects both India’s grid build-out and the company’s expanding share of it. In November 2026, Mumbai investment firm ValueQuest announced new investment commitments in Rational Engineers alongside Sagar Defence Engineering, as part of ₹775 crore of commitments across three Indian manufacturing and defence businesses. The firm said the investments reflect its conviction in India’s growing role in global industrial supply chains and in building sovereign capabilities in strategically important industries.
India is adding transmission capacity, electrifying railways, expanding renewable energy and upgrading distribution networks at a pace the country has never attempted before. Every one of those projects needs transformers, and every transformer needs windings. The copper thread running through that entire build-out is, increasingly, wound in Thane. Rational Engineers has spent 37 years becoming the company the grid builders call first — and the next decade of India’s electrification will run, quite literally, through its conductors.
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