With this successful breakthrough, ABB becomes the first supplier worldwide to design and realize this kind of function in a hoist system, according to the company. This function will greatly reduce the maintenance time and increase the reliability and availability of coal mine production.

The Ma JiaLiang coal mine is a major construction project of Shanxi Province with a planned annual production capacity of 12 million metric tons (mt) of coal and maximum capacity of 15 million mt. When put in operation, it will be the coal mine shaft with the highest production in China.

ABB provided two hoist systems for the main shaft, with each hoist pulley having a diameter of 5.7 m, a payload of 45 mt, and a motor power of 7,000 kW. It uses MV AC-DC-AC direct torque control (DTC) technology and is the largest hoist system ever installed in China.

In June 2011, ABB started the installation and no-load commissioning of the mine s No. 2 main shaft hoist, which covers the mechanical part, the motor, the control system, as well as the ACS 6000 MV drive and brake control system. The half-speed under full-load function is designed to maintain the safety of the hoist system and a continued production in case of failure of the hoists drive system. Half-speed with full-load redundancy has been available for systems using DC drives and AC-AC direct conversion frequency drives, but this specific function has never been realized before for hoist systems based on AC-DC-AC frequency conversion drives.

Stephen Zhu, manager of ABB’s mining and minerals business in China, said ABB designed the drive system using two independent sets of active rectifier units (ARU) and inverter units (INU) for the Ma JiaLiang project. Under normal conditions, the two operate together, providing power to the motor. If one fails, a switch cabinet will connect the redundancy operation mode and start the operational set. This is a significant achievement which can greatly reduce shutdown time, providing our customers continuous production with improved reliability.