Safety and performance optimization of industrial cranes
Hoisting of equipment and goods in production or in transportation is a common function across all heavy industries, performed by cranes. And the drive to improve safety in working conditions and efficiency in operations mean that cranes increasingly contribute to improve heavy industries.
Some of the most common industrial cranes are overhead travelling cranes and gantry cranes. In these cranes the load is suspended from a gripping device by cables, and acts like a pendulum. These swaying loads are a safety hazard and place additional stress on the crane structure. The solution is to control the motion closely using an AC drive on the input to the electric motor.
Brake control, energy storage and more
The user experience of the crane consists of many factors. AC drives from Danfoss offer crane-dedicated features which enhance performance in a myriad of ways:
For open loop operation, Danfoss drives help to ensure excellent crane performance without encoders. The crane is simple to commission for travel and hoist. For parallel operation of two motors, droop control equalizes torque between the two motors.
Cranes achieve better dynamics in closed loop operation. Danfoss offers flexible encoder interfaces, enabling broader choice of components
Advanced mechanical brake control
Danfoss drives prevent load shocks at start and stop of lifting. For vertical motion, Danfoss provides smooth torque ramping to ensure that the load is held, stopped, raised and lowered in a perfectly safe mode at all times.
For closed loop operation, the master drive is speed controlled and transmits a torque reference to the follower drives via analog output or fieldbus. The follower drive works in torque control mode and master drive works in speed control mode.
Danfoss AC drives are well-suited to this task of stabilizing swaying loads since they are equipped with integrated sensorless anti-sway software. The anti-sway function takes account of the hoist and load type to ensure the load remains stable and does not sway. The anti-sway function improves safety, reduces cycle time to improve productivity and requires no special operator skills.
The braking energy of a crane is traditionally lost as heat. However, by capturing this braking energy using a regenerative drive, it can be put to work to improve energy efficiency. Danfoss AC drives are available with Active Front End (AFE) for regenerative capacity
Using a combination of diesel and battery-stored electrical energy creates opportunities to shave peak loads, optimize use of cheaper off-peak power, and maintain operation in the event of power cuts.
- Shift consumption from the grid to off-peak periods. By charging batteries at nighttime off-peak rates, then using the stored power as the demand arises during the working day, crane operators can use time-shifting to reduce electricity costs for daily operations.
- Peak load shaving for incoming power. By using battery-stored power to boost peak load demands, for example when high torque is requied at the start of a lifting operation, the electric motors are shielded from the peak load demands. Ultimately this means the crane manufacturer can dimension the motors to the regular load, rather than to the peak load.
- Back-up power or black-out start. Use battery backup to replace spinning reserve that might be otherwise achieved by running diesel generators. As batteries become gets cheaper, the viability of integrating batteries in cranes for back-up in the event of power supply failure, increases.
Features and benefits
Easy commissioning thanks to built-in crane-dedicated features
Smooth operation with no jerks or oscillations during startup and ramping
Tandem load balancing for trolley and travel applications, via speed-torque sharing or load drop control
Tandem hoist, synchronizing the shaft speed between two hoists
Choice of open loop or closed loop control
Mechanical brake for smooth operation and optimal safety
Controlled stop in the event of dropping a load
Integrated crane safety software ensures legal compliance with functional safety STOP functions: Safe Torque Off, SS1, SS2, SQS and more
Anti-sway control to ensure highly stable transverse movement
Crane applications served by Danfoss drives
- Hoist: Lifting and lowering of the load.
- Bridge, gantry, or long travel: The part of an overhead crane consisting of girders, trucks, end ties, walkway and drive mechanism which carries the trolley and travels in a direction parallel to the runway.
- Trolley, or cross travel: The unit carrying the hoisting mechanism which travels on the bridge rails. The trolley run on a single motor or two motors coupled with common shaft.
- Jib or boom: The horizontal member supporting a moveable hoist fixed to a wall or to a floor-mounted pillar is known as a jib crane.
- Slewing: The angular movement of a crane boom or crane jib in the horizontal plane, as seen for example in tower cranes.
Crane types served by Danfoss drives
- Overhead crane
- Process crane
- Rail-mounted gantry crane
- Rubber tired gantry crane
- Goliath crane
- Grab crane
- Ship to shore (STS) container crane
- Marine crane
- Mobile crane
- Mobile harbor cane
- Tower crane
- Construction hoist
Danfoss Drives offers personal advice and application design from our drives experts to support OEMs, system integrators and industrial users. We also provide customized solutions for hardware and software that enable seamless integration and a range of features that optimize the total system.
Danfoss Drives is a leading supplier of AC drives for the cranes industry. More than 100,000 Danfoss drives are providing effortless speed control and optimized efficiency for the smallest chain hoists up to the largest mobile crane vessels with lifting capacities up to 10,000 tons.
Solutions for new developments and modernizations
When designing new cranes, Danfoss Drives is able to draw on years of experience related to applications and AC-drives technology to support the development.
Cooperation in analyzing the operation of drives using test cranes, and optimization of the controls, performance and system as a whole, are important areas of our expertise. And our wide service offering covers scheduled maintenance requirements and optimization of modernization packages.
Danfoss Drives’ engineering support and service teams are capable of assisting system integrators and crane manufacturers at all stages of projects from cabinet building to commissioning. Covering the full lifetime of the crane, our key services include technical support, start-up, maintenance, spare parts, upgrades and training.