An optional software add-on for the ABB industrial drives range, covering the vast majority of crane applications from 0.55kW to 5,600kW, incorporates all the functions commonly required for the hoist, trolley and long travel motions of industrial, harbour and tower cranes.
At the heart of the design is ABB’s motor control platform, Direct Torque Control (DTC). DTC technology allows accurate control of speed and torque with or without pulse encoder feedback from the motor shaft. The Crane Control Program utilises DTC to deliver enhanced operational safety and provides accurate slow speed control with high torque levels. The program offers flexible interfaces for different types of analogue, digital or fieldbus based systems, enabling a wide range of connectivity for start, stop and reference change signals.
Function block programming - known as adaptive programming - eliminates the need for an external PLC. The 15 function blocks are easy to programme using the drive’s control panel, while adaptive programming enables the user to integrate external control logic or create new functions in order to customise the application.
Torque ‘memory’
The program features integrated brake control logic, which in turn, utilises torque memory and pre-magnetising to open and close a mechanical brake safely and reliably. Mechanical braking effort is spring applied and electrically released when the drive system has been started and torque applied to the motor shaft. The program can accommodate different start torque methods, and it also includes a brake monitoring function for start, stop or running sequences. In addition, programmable counters provide information on total crane operating time and the number of times the brake has been operated.
In a master/follower application, the system is operated by a number of drives which are interlinked by fibre optics. The system can be designed for a maximum of five motors, either with a common drum and separate motors with load sharing, or with separate drums and separate motors with shaft synchro control. Fast switch-over logic, between stand-alone mode and master/follower mode, is incorporated. The homing function is used to calibrate the actual position value to a reference value to ensure that lift hooks are in the correct start position.
A crane system check function is provided that includes both electrical and mechanical checks. Torque proving ensures that the drive and motor are able to produce torque and that the mechanical brake does not slip before the drive releases the brake and starts operating the crane. Meanwhile, load speed control maximizes the hoist speed for the given load and ensures that there is sufficient motor torque in the field weakening area. This minimizes operating time and optimizes crane capacity.
Safety
The ‘slow down’ safety control function limits the speed to a preset level in critical zones. High and low limit sensors stop the drive at the end positions. The ‘fast stop’ safety control function is used in emergency situations. The speed monitor function ensures that the crane motor speed remains within safe limits to prevent over speed. A speed matching function continuously compares the speed reference and the actual motor shaft speed to detect any possible difference. And one of these functions will stop the motor immediately if a motor fault should occur.