Electricity + Control June 2017

STANDBY + BACK-UP PLANT MAINTENANCE, TEST + MEASUREMENT

• Aluminium windings and copper windings give transformers the same quality of operation and per- formance. • Aluminium-wound transformers do not have bigger losses of electricity. • Global specialist, WEG Transformers, successfully manufactures transformers with aluminiumwindings.

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shortage of copper, which was in huge demand for the arms industry. By the 1960s, when copper prices rocketed due to high demand, aluminium again became popular in windings; previous technological problems were overcome, and these transformers became more reliable. Since 1970, aluminium was used intensively in the United States and the technology of alumini- um-wound transformers was further enhanced; it has now gained widespread acceptance in European countries and other parts of the world. Just a myth One of the myths that has been disproved is the belief that alumini- um-wound transformers have bigger losses of electricity. While the aluminium conductors are larger than copper conductors, they are lighter; the result is that the mass of the core in an aluminium trans- former is 5 to 20% more, but the total transformer mass is almost the same – for the same level of electrical loss. Temperatures With regard to the respective thermal properties, aluminium has a lower melting point than copper but it is still well above the real working temperatures of the windings. In normal circumstances, the ‘hot-spot’ temperature in the windings is between 105°C and 120°C, while aluminium only melts at 665°C. More importantly, the lower thermal conductivity of aluminium does not affect the performance; the temperature differences in the conductor are negligible in rela- tion to the temperature difference between the ambient air and the windings. Also, as a result of the difference in the material properties of the two metals, Eddy loss in aluminium winding is 38 % less than in copper with the same volume of conductor. Conclusion While there was historically some concern about joining and terminat- ing aluminium – either to itself or to copper – when it was to be used outdoors, these joints and terminations are today made without any problems. Techniques such as bolting, crimping and arc welding un- der inert gas (with or without refractory electrodes) have undergone severe testing over many years and have been proven.

Aluminium bus bar.

Aluminium coil.

Winding underway at WTA's Wadeville manufacturing facility.

Aluminium connectors.

Enquiries: Tel. +27 (0) 11 723 6000 or email marketing@zestweg.com Visit www.zestweg.com

June ‘17 Electricity+Control

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