Steel giant automates world's second largest crane

Redditch, UK - The Usiminas steel plant in Brazil has automated what, it claims, is the world's second largest crane: providing 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 8 metres per minute. The project was carried out in collaboration with WEG, which supplied a full turnkey system including, transformers, MV motors, and MV frequency inverters.

The crane at Usiminas' plant in Ipatinga, Minas Gerais, Brazil, 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 includes the power supply at medium voltage (with transformer and cubicles at 3.3 kV), and the supply to the WEG MVW-01 MV drives and M-Line range of motors.

According to WEG, the motors have been designed specifically for this application and incorporate speed sensor encoder and independent forced ventilation. This system, it adds, is designed 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 use coils that are specially designed to suit the voltage and the application for which the motor is intended. Another feature is the epoxy-based resin Vacuum Pressure Impregnation system to enhance insulation quality and stator coil protection of the motor windings.

WEG's package for Usiminas package also includes its new MVW-01 range of medium voltage drives, which offer 99%efficiency via a new design that employs Multilevel Topology to minimise component levels, and high voltage (6.5kV) IBGT’s 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,” said 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."