The Evolution of Transformers and Coils in Power Supply Applications

The advancement of control ICs running at higher frequencies allow power supplies to be smaller and more efficient. The wound components must cope with this higher expectation.

The advancements in transformers and coils

  • Ferrite core material
    Ferrites used in power applications now have lower losses, leading to greater efficiency. They are capable of operating at higher frequencies. They demonstrate more stability across a wider range of temperatures, frequencies and currents.
  • Size to Power relationship changes
    The higher frequency allows units to produce the same power, but be physically smaller. Smaller wound components must match this size reduction, which they have been able to do, with the ferrite coping at higher frequencies.
  • Insulation requirements
    As the wound components get smaller there is less room for the insulation required to prevent voltage breakdown. This has led to a change in materials and construction methods.
  • Conductor changes
    The use of higher frequencies has led to changes in the conductors used, in order to ensure there is little or no “skin effect” with larger CSA conductors, but, even though there may be fewer turns in the newer wound components, the conductor must still be capable of carrying the required current.
  • New Standard Requirements
    The higher technical demands on power supply components now include smaller and lower rated power units. This means more components are being encompassed within tighter technical specifications. A good example is the Partial Discharge requirements that now encompass smaller power supplies and management, as well as the traditional power transmission requirements. This is particularly pertinent within the renewable energy industry where the life of a component is critical e.g. In an off –shore wind turbine.

How these changes affect transformers and coils

  1. The use of different core material, such as nano-crystalline and specialised metals
  2. The use of multi-stranded Litz wire and copper foil, to cope with the “skin effect” caused by the higher frequencies.
  3. The use of triple insulated wire to give excellent insulation and still meet the creepage and clearance requirements in smaller coils.
  4. Increased use of insulation margin tape, sleeving, and encapsulation to offer protection.
  5. The development of different core styles, such as planar.
  6. More onerous testing, especially high voltage insulation and partial discharge.

How AGW have evolved with the changes

  • Winding methods
    Alongside the traditional ferrite core and bobbin shapes and sizes, AGW are able to wind self bonding air coils, wave wound coils, copper strip coils and supply planar coils. We have the facility and expertise to use the various wire types and are able to manufacture the items that require intricate insulation construction.
  • Materials
    We have experience using the Stranded Litz Wire, the Triple Insulated Wire. We are aware of the lower loss ferrites for design purposes. We have developed knowledge regarding the preferred bobbin material and encapsulation material to reduce and remove the occurance of partial discharge.
  • Manufacturing facilities
    AGW has the varnish and impregnation facilities that are now required to ensure that coils meet the insulation and environmental requirements. These facilities include the use of vacuum impregnation.
  • Testing methods
    AGW have automated production testing, in order to 100% test all items. AGW also has the facility to measure Q readings, in order to tune coils to be their most effective. AGW is able to carry out high voltage breakdown and impulse testing. AGW invested in partial discharge testing equipment and now has an automated system to carry out partial discharge testing to 20kV.

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