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Harwell’s particle accelerator transformed by Carroll and Meynell

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As part of a major project to allow the ISIS Synchrotron Particle Accelerator* at Harwell’s Rutherford Laboratory to move forward into the 21st century with new and innovative research projects, the power supply for the magnets that contain the proton beams and accelerate them to 84% of the speed of light, is being up-graded.

As part of this upgrade Carroll & Meynell Transformers was asked to supply a 1.2MVA single phase transformer to a very exacting specification. The customer specified a particular voltage per turn ratio in order to meet their exact requirements electrically and imposed a height restriction for access purposes.  Both of these factors combined to make very specific demands on the design of the thermal management of the unit, terms of conductor size and cooling ducts.  

This challenging project required the Carroll & Meynell design and engineering team to revise and upgrade the transformer design methods to achieve an operating design that met the standards. It also required the development of new tooling and production engineering methods to perform the construction and assembly of the unit. The engineering developments for this project have expanded the capability of Carroll & Meynell to manufacture dry type transformer units up to 2.0MVA.

The 1.2 MVA transformer is a three phase to single phase unit with multiple primary taps.  The input to the transformer included a Steinmetz LC circuit and a phase controlled power factor correction system that ensured balanced current loading from the 3 phase supply.

The transformer had a 480V – 0V – 240V -480V primary tapped winding. The three phase supply connections are to the 480V – 0V – 240V taps with the other 480V line being stepped up to operate the power factor correction system.

The output is nominally 800V – 0V – 800V single phase with a set of trim taps to supply a series of capacitor banks and reactor in resonant circuits that provide the AC power components to the magnets of a particle accelerator

*ISIS is a world-leading research centre in the physical and life sciences which has changed the way the world conducts neutron scattering research. The ISIS synchrotron accelerator works by accelerating protons to 84% of the speed of light ad then firing them into two tungsten targets. This releases neutrons which scientists use to study the atomic structure of materials and even measure the forces between atoms

About Carroll & Meynell

From its design and manufacturing facility in Stockton-on-Tees, Carroll & Meynell Transformers Ltd has excelled in the design and manufacture of high quality transformers and coil wound products for over 40 years. Founded in 1970 , it is still a family-run business under the direction of co-founder Mike Meynell. In 2000 the business moved to its current location to accommodate the company’s continued growth and expansion, where it now occupies a 30,000 ft² site.

Market leader for several years in the UK for construction industry products, Carroll & Meynell Transformers now provides power solutions to a wide range of industries including traction, railway infrastructure and signalling, marine (ROV),  aerospace, mining and power generation / distribution.

Today the company’s emphasis is on bespoke designs to meet our customers’ specific requirements, and achieve the best and most cost effective solutions.

Environmentally conscious, all of our products have been reviewed and found to be compliant with the EU Ecodesign Directive 548/2014


Our product portfolio comprises small panel transformers from 50VA single and 3 phase power transformers up to 2MVA, 

Our product range includes: 

  • High frequency high power transformers up to 50 kHz, 200kW
  • High voltage transformers up to 7.2KV
  • Bespoke single phase transformers (50VA – 1.5MVA)
  • Bespoke three phase transformers (50VA – 2.0 MVA)
  • Current transformers
  • Single and three phase variable transformers
  • UK to US supply conversion
  • Enclosed Transformers – IP67
  • Low voltage high current transformers  (eg for heating systems)
  • 3ph – single phase conversion (Open Delta) transformers
  • K Factor transformers
  • Panel transformers
  • Motor start Korndoffer transformers
  • Toroidal transformers
  • Cathodic protection transformers
  • Portable tool transformers
  • Energy recovery applications
  • Power distribution systems 
  • Power factor correction products
  • Chokes and inductors (50Hz – 100KHz)
  • DC power supplies

All of our non-exempt transformers comply with EU Ecodesign Directive No. 548/2014


High-end magnetics

Carroll & Meynell manufactures a wide range of magnetics for a large number of varied applications; one of the very few companies in Europe which incorporates the design, development and manufacturing functions on a single site. Our capabilities range from 50VA to 2 MVA in the case of single phase, three phase, poly phase and phase conversion low frequency (50/60Hz) transformers.

Our design and development team is continuously working on the development and improvement of advanced mathematical models that define the optimum selection of constructions, core material combinations and conductor arrangements. These analyses are carried out based on application specific approaches which give a parametric approach to the designs. This approach enables us to arrive at the best possible design solutions for demanding magnetic applications in modern environments where in most cases the transformers and inductors are subjected to higher order harmonics of significant amplitudes. 

Applications include modern power electronics applications such as high power AC/ DC ,  DC /DC , AC/AC converters used in rail, traction, renewable energy and similar applications , uninterrupted power supplies, and high K-factor transformers.  Furthermore Carroll & Meynell is a leader in addressing the challenges to magnetic designs for the newel power electronics developments made with the emergence of SiC MOSFET technology, something which has drawn the attention of industry experts at symposia such as PCIM.

Materials optimisation

In addition to the conventional transformer core materials such as standard non-oriented lamination steel, and grain oriented silicon steel, we work with a wide range of core materials such as Amorphous, Nanocrystalline, the latest high temperature rated ferrite, high-silicon content steel and a range of standard ferrites, enabling us to carry out application specific material optimisation.  This has given us a competitive edge in developing magnetics with minimal acoustic noise optimal efficiency for specific applications.  

Our high frequency transformers, which range from 1kW to 200kW, can be engineered using different grades of ferrite, including the new 3C97 which has higher power density and a wider operating temperature range. We are also producing competitive designs for high frequency transformers with Nanocrystalline core material and controllable leakage inductance techniques.

In terms of noise-minimisation our capability already exceeds current industry requirements. When combined with the use of appropriate materials we are more than adequately equipped to meet any anticipate future standards in respect of the noise levels at higher frequencies which irritate animals.  

By applying the optimum selection of core materials and conductor types, we can create solutions which produce better performance, compact size and reduced cost in application areas such as traction, renewable energy and dc-dc power conversion.

Power electronics applications

As the leading power electronics companies strive towards the further miniaturisation of inverters and converters in high power applications, we are working hand in hand with them to build up a family of compatible transformers and inductors. We have already successfully achieved 50kW in 50kHz applications and are close to attaining powers as high as 200kW in 20kHz applications.

We are also working towards the development of customized finite element simulation tools in association with the research groups based in leading universities. These enable a better visualization of electromagnetic behaviours in complicated practical applications.

A current high profile project involved the incorporation of passive power factor correction stages to rectification units that substantially reduces the complexity and EMC generation of these units.  In addition to raising the overall efficiency to the order of 98% this concept has given us the possibility of developing stable Electric Vehicle chargers which can fast charge up to 10 standard EV cars or 4 Tesla cars at one go handling a total power of up to 500kW.

Our new brochure provides detailed information about our specific range of products. To request a copy, or to speak to one of our team to discuss your individual requirements, please contact us on:

Tel: +44 (01642) 617406


Or visit our website


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