Dedicated crane control program
06 January 2009
Crane control software that brings increased safety, reliability and improved performance to industrial, harbour and tower cranes has been developed by ABB for use with its variable speed drives.
Called crane control program, the software is an optional add-on for the ABB industrial drives range which extends from 0.55 kW to 5600 kW. It incorporates all the functions commonly required for the hoist, trolley and long travel motions in 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 utilizes DTC to deliver enhanced operational safety and provides accurate slow speed control with high torque levels.
Flexible control platform
The crane control program offers flexible interfaces for different types of analogue, digital or fieldbus 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 program using the drive’s control panel. Adaptive programming enables the user to integrate external control logics or create new functions, so the software can be customized quickly and easily.
Mechanical brake control and torque memory
The program features an integrated brake control logic which in turn utilizes torque memory and pre-magnetizing to open and close the mechanical brake safely and reliably. The mechanical brake is applied by a spring and is electrically released when the drive system has been started and torque applied to the motor shaft.
The crane control program can accommodate different start torque methods, and it also includes a brake monitoring function for start, stop or running sequences.
The software incorporates programmable counters to provide information on total crane operating time and the number of times the mechanical brake is used.
Master/follower and shaft synchro control
In a master/follower application, the system is operated by a number of drives which are interlinked by fibre optics for reliable control. 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 the hooks are in the correct start position.
Crane system check
A crane system check function 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.
Load speed control
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.
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.
Speed monitor and speed matching
The speed monitor function ensures that the crane motor speed remains within safe limits to prevent over speed. The speed matching function continuously compares the speed reference and the actual motor shaft speed to detect any possible difference. One of these functions will stop the motor immediately if a fault should occur in the operation of the motor.
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