Turnkey MV motor system moves monster crane

Transformers, motors and frequency inverters are used to automate the second largest overhead crane in the world, at the Usiminas steel plant in Brazil.

WEG has supplied a full turnkey system including transformers, MV motors and MV frequency inverters to automate the second largest overhead crane in the world, at the Usiminas steel plant in Brazil, one of the largest in the world.

The crane provides a 260-tonne lifting capacity on its main hook, and 40 tonnes on its auxiliary hook, while transporting molten steel at speeds of up to 8m/min.

Usiminas the largest producer of iron and steel industry in Brazil, is also one of the most profitable in the world, currently producing over 9.5Mt of steel a year for the global market.

At its plant in Ipatinga, Minas Gerais, Brazil, Usimas employs the second largest overhead crane in the world.

The crane is used to carry molten metal, and is one of the very few in the world to be controlled by a PLC and digital frequency inverters connected over the Profibus-DP communication network.

The WEG system for the overhead crane includes the power supply at medium voltage (with transformer and cubicles at 3.3kV), and the supply to the WEG MVW-01 MV drives and M-Line range of motors.

The motors, for example, have been designed specifically for this application, and incorporate speed sensor (encoder) and independent forced ventilation.

One of the major advantages of this bespoke solution is the operating flexibility and safety inherent in the system.

This is the result of designing the system to accept failure of one or two of the four motors that drive the main lifting of bucket that carries the molten steel.

WEG's MV motors and drives are ideal for use in steelworks, as they are designed for use in some of the most arduous operating environments imaginable; notably offshore oil and gas installations where robustness, reliability are safety are paramount.

To ensure reliable, long life operation in the demanding applications, WEG's MV motors use coils that are specially designed to suit the voltage and the application for which the motor is intended.

Further aiding reliability is WEG's state-of the-art (and environmentally friendly) VPI (vacuum pressure impregnation) system.

This guarantees high quality insulation and stator coil protection through the application of a special epoxy based resin to the motor windings.

Optimising the performance of WEG's MV motors in the Usiminas package is the new MVW-01 range of MV drives.

These set a new benchmark for medium voltage (MV) drive efficiency, achieving 99% with a new design that employs multilevel topology to minimise component levels, and high-voltage (6.5kV) IBGTs to reduce motor harmonic currents to extremely low levels.

"Usiminas has a policy of investing in new technologies, so we decided, in partnership with WEG, to develop a new control package for our high capacity crane", says Ney Otaviano Batista Leite, Electrical-Electronic Project Engineer at Usiminas.

"This was not easy as the crane carries molten metal and is subject to the most stringent safety requirements".

"Initially there was some resistance to using frequency inverters, but WEG convinced us of the benefits".

"WEG has a long association with Usiminas, and is a recommended supplier for all our control needs".

"We also use WEG for the high levels of after sale support provided; as evidence of this, the support on the turnkey package for the crane has been highly satisfactory".

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