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Efficient Tap Changing for Arc Melting

Aug. 22, 2011
Reduced maintenance, higher availability and reliability for transformers
With a maintenance interval of 300,000 switching operations, the Vacutap VM on-load tap-changer reduces maintenance downtime in applications with a high number of tap-change operations, such as arc furnaces.

Maschinenfabrik Reinhausen GmbH (MR) is offering a new on-load tap-changer that matches the reliability and efficiency required for electric arc melting. Such operations depend on a reliable transformer, and an on-load tap-changer ensures process voltage control. With MR’s Vacutap® VM, The retrofitable vacuum switching device significantly reduces maintenance requirements, and thus downtime, and its arc control and step protection system protects against damage to the tap-changer and transformer.

The process reliability of melting operations places special demands on the supply of power. Optimal voltage regulation and switching strategies that are designed to meet demands are essential for consistent performance and quality. The on-load tap-changer meets these demands in the process and furnace transformer. The new Vacutap VM offers advantages that contribute to greater efficiency, and has innovative details that increase operational reliability in vacuum switching technology.

With a maintenance interval of 300,000 switching operations without time or electricity criteria and a contact life of 600,000 switching operations, the Vacutap VM is designed for industrial applications with a very high number of switching operations. The lifespan of the diverter switch unit is 1.2 million switching operations. As the on-load tap-changer oil is not polluted by the arc extinction in vacuum switching technology, neither an oil filter system nor the associated filter changes are required.

With 200,000 switching operations per year, normal in metal production, and a transformer lifespan of 20 years, up to 45% of the costs for maintenance, spare parts and oil filters can be saved with the Vacutap VM, compared with conventional oil switching tap-changers (maintenance is required after 40,000 to 100,000 switching operations.)

The interrupter exchange module helps to reduce downtime due to maintenance when the vacuum valves need to be exchanged after 600,000 tap-change operations. This intelligent spare-part solution consists of a completely assembled and preconfigured module, including a supporting unit that allows a simple, timesaving change to ensure a fast return to service for the transformer.

Oil transformers can be converted into vacuum transformers just as easily thanks to the retrofitable diverter switch insert of the new Vacutap VM, with complete connection compatibility to the Oiltap M/MS. This allows the diverter switch insert to be exchanged in a plug-and-play procedure.