The core space factors, used as a measure in this regard, vary between 10 to 30%, depending on the insulating class of the windings, which results in a marginal increase for the magnetic circuit of approximately 10 to 20%. [4] This means that electrical connections at the ends can be made without stripping off the insulation first. the same efficiency? 7-22, Joseph, Günter, 1999, Copper: Its Trade, Manufacture, Use, and Environmental Status, edited by Kundig, Konrad J.A., ASM International Vol. The cost difference between copper and aluminium varies as a result of the fluctuating cost of the base metals on the commodities market. For large power transformers, a copper–copper design is more common. For most dry type transformer applications, copper windings are the industry standard, although both types are commonly used. When factors such as chemical, physical, and mechanical property requirements are considered, copper is considered the first choice conductor for magnet wire.[1]. In the case of oil cooled transformers, it is recognised that the catalytic action of aluminium on oil oxidation is significantly less than those with copper. Aluminum has only 62% of the electrical conductivity of copper, making copper a much more effective conductor. Self-supporting coils are wound with wire coated with at least two layers, the outermost being a thermoplastic that bonds the turns together when heated. Magnet wire or enameled wire is a copper or aluminium wire coated with a very thin layer of insulation. To obtain equal ratings in aluminium transformers, a 66% larger cross-sectional area is required than for copper conductors. However, the use of larger-sized conductors results in aluminium winding strength nearly equivalent to copper windings. To select the right material, the designer has to take several factors, such as weight, maximum size, transformer total cost, availability and cost of the material, into consideration. The skin effect causes the effective resistance of the conductor to increase at higher frequencies where the skin depth is smaller, thus reducing the effective cross section of the conductor. As described above, a few minor adjustments on windings supports and spacers is enough to achieve the same mechanical integrity of transformer with aluminium windings as in the case of copper. So, the value of current density in copper conductor in coil is kept around 2.5 - 3.5 Amp/sq.mm . In modern designs, thanks to advancements that allow for reduced copper winding heat loss, copper windings often outrank aluminum windings in their long-term operational cost-effectiveness. Find expert, Guide to Oil-Filled Transformer Maintenance, Guide to Dry Type Transformer Maintenance, 4 Signs Your Dry Type Transformer Needs Repaired. WEG Transformers has successfully manufactured thousands of distribution and hundreds of small power transformers with aluminium windings. Therefore for equal losses, the aluminium-oil temperature gradient will be smaller than the copper-oil gradient. Both will give the user a transformer with the same quality of performance operation. For small products, the wire must be strong enough to be wound without breakage, yet flexible enough to provide close-packed windings. Although modern design improvements have let transformer experts navigate the technical problems associated with aluminum, copper is typically a superior option for protection against fault current stresses and overall longevity. Aluminium is used in a number of industrial applications, and some 200 aluminium alloys are available on the market. The lower thermal conductivity of aluminium does not affect the performance in the overall temperature of the transformer and the temperature differences in the conductor are negligible in relation to the temperature rise between the ambient air and the windings (gradient). In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. Dry type transformers typically feature either copper or aluminum windings, also known as coils. For example, to reduce load losses in continuous-use induction-type motors above 1 horsepower, manufacturers invariably use copper as the conducting material in windings. ancements that allow for reduced copper winding heat loss, copper windings often outrank aluminum windings in their long-term operational cost-effectiveness. Older insulation materials included cotton, paper, or silk, but these are only useful for low-temperature applications (up to 105°C). This larger cross-sectional area translates to a lower current density and an equivalent operating temperature. There are no significant differences in this regard between the design applying aluminium or copper windings. Copper windings usually feature tighter coils that can also be optimized for lower current density. The most suitable materials for magnet wire applications are unalloyed pure metals, particularly copper.