Hold steady

The ACS800 drives with the anti-sway control program are specifically designed for indoor crane use, and replace the existing drives without the need for external sensors or other hardware.

Grabs on two electrical overhead travelling (EOT) cranes at Renova AB’s Gothenburg facility transport household and industrial waste from a 22,000m3 bunker to a feeder shaft. This then feeds the plant’s three furnaces, which generate around 220,000MWh of electricity a year. The grabs can carry up to 5t of waste in one lift.

The cranes each use two 15 kW motors on the long-travel movement, while the trolleys are powered by one 7.5 kW motor. Both motions use ABB’s motor control platform, direct torque control (DTC), in open loop mode. The hoist has one 200 kW motor in closed loop DTC mode, which uses an incremental pulse encoder to generate speed feedback.

Preconfigured control programs within the drives give accurate and stable control of the load. The ABB crane control program, for instance, is used in hoist movement for precise lifting and lowering of the load.

The ABB anti-sway control program is installed in the trolley and long travel drives, enabling them to control the load sway without additional hardware such as anti-sway sensors. The drives are connected to each other through an optical link to share feedback information on the hook position. The program gives the operator better crane control, cutting the time to feed waste to the furnace and maximising the amount of waste handled in a day.

Mihkel Albo, electrical manager of Renova AB says: “The anti-sway function is easy to use, which is especially crucial when a crane driver does not have a lot of experience. Reliability of the crane is the key to shortening the waste handling time in the bunker and avoiding downtime to achieve an optimised process.”

ABB’s drives were needed as the existing low voltage AC drives used on the cranes were coming to the end of their life cycle and needed upgrading. The major requirement was to optimize the waste handling process. With the plant operating 24 hours a day, seven days a week, a highly reliable, accurate and stable crane control system was needed in order to maximise process uptime.

“Compared to the previous drives, the new AC drives feature DTC, which improves the process control, enabling fast start and stop of motors. Using regenerative drives provides quicker acceleration and deceleration time of the motor, thus shortening cycle time,” says Albo.