With the continuous development of China's construction industry and the improvement of construction mechanization level, tower crane's manufacturing, technical level and overall performance requirements are higher and higher. The system control level of tower crane, the operability and maintainability of users basically reflect the technical level of tower crane. The mechanical impact produced in the process of speed regulation will directly affect the performance of the whole machine.
Variable frequency stepless speed regulation is a kind of AC speed regulation technology, which surpasses any other speed regulating methods with relative advantages. Its advantages are numerous, such as: low frequency, high torque, slow positioning speed, long-time operation, fast start and stop, zero speed braking, stable operation without impact, which can extend the service life of mechanical structure and transmission device, and greatly improve the safety and reliability of tower crane.
Traditional tower crane control scheme
Traditional small and medium-sized tower cranes are generally controlled by contactors, which have great impact on machinery due to large speed jump, complex circuit, poor reliability of contact contact contact and inconvenient installation and maintenance.
1. The hoisting mechanism is an important transmission mechanism of tower crane. The control mode mostly adopts winding rotor motor series resistance speed regulation or multi speed motor pole changing speed regulation. The circuit is complex, has great impact on machinery, frequent positive and negative rotation, easy to damage contactor contact, high failure rate, and is not easy to maintain.
2. Rotary mechanism is a load with large inertia, which has large impact on starting, difficult positioning and frequent reverse gear stopping, which will cause great damage to the mechanical transmission mechanism. Improper operation will easily cause tower body distortion, and in serious cases, it will cause tower crane arm folding, which will cause great safety risks to people and equipment. The traditional control method is to use winding motor series resistance or torque motor for speed regulation. These two control methods can't carry out smooth speed regulation in the process of starting and stopping, which will cause shaking of the rotating arm.
3. The luffing mechanism adopts multi speed motor pole changing speed regulation, step action and mechanical vibration are large, and the heavy objects are easy to shake in the air during the operation, and there are potential safety hazards.
Tower crane frequency conversion integrated control scheme
LD500T series tower crane integrated special driver is a medium and high-end model, which is intelligent modular and lightweight designed for tower crane electric control requirements. It integrates the frequency conversion control unit, logic control unit and black box monitoring unit (extension) of lifting, slewing and luffing mechanism. It can improve the safety and stability of tower crane and solve the problems of equipment maintenance difficulty, and provide a high-performance and complete tower crane system solution for customers.
1. The lifting mechanism uses frequency converter to drive three-phase asynchronous motor to replace the traditional speed control mode, which can improve the operation efficiency, eliminate the impact of starting and braking, and reduce the failure rate of electrical system. Moreover, the frequency conversion speed regulation technology is advanced and the control is simple. It is an ideal transmission control device for the lifting mechanism.
2. The rotary mechanism adopts frequency converter stepless speed regulation and flexible torque control. The "flexible with rigid" inching is powerful and fast response, which makes it more stable when starting and braking, so as to avoid the shaking of tower arm and greatly improve the safety performance of tower crane.
3. The luffing mechanism uses frequency converter to drive ordinary squirrel cage motor instead of pole changing speed regulation of multi speed motor. By dynamically adjusting the frequency and acceleration and deceleration time of the frequency converter, the swing is limited and its operation is more stable.
4. The system adopts PL logic control, the input and output have clear status indication, the circuit is simple, the installation and maintenance are extremely convenient; the safety and braking circuit realize the dual interlock of logic software and hardware, and the safety is more guaranteed.
Application advantages of LD500T series tower crane integrated special driver
1. It adopts full frequency conversion and modular design, with perfect functions; the hoisting, slewing and luffing mechanisms operate independently and do not affect each other.
2. When the brake fails due to mechanical reasons, the stall protection and zero servo hover function provide double protection to prevent hook slipping accident (closed-loop mode).
3. Light load or empty hook, enter light load high-speed mode, automatic overclocking, improve work efficiency.
4. According to the input voltage, adjust the V / F ratio dynamically and output enough torque to ensure the safety and reliability of the lifting mechanism.
5. Through the brake release frequency, brake release current, brake release time and brake closing time, the special brake holding logic control is realized to ensure the safety and reliability of the system.
6. Almost zero speed brake and zero speed brake, soft start and soft stop, prolong the service life of brake.
7. Flexible torque control, stable operation, no need to frequently reverse gear parking, fast stop in place. It can return to zero directly from high speed gear, and the working efficiency is greatly improved.
8. The logic input and output have clear LED indication and silk screen mark, which solves the problems of field installation and maintenance inconvenience.
9. Expand the remote monitoring module, establish intelligent management system of construction machinery, realize on-line monitoring, remote fault diagnosis, and provide customers with a larger range of value-added services.
10. Intelligent management system of construction machinery: it monitors whether the tower crane is overweight or over torque, records the alarm information, and feeds back to the project supervisor in real time to prevent the occurrence of tower crane safety accidents, which plays an important role in safety monitoring and management.
