Tower crane is aimed at Mold Technology of caution heavy plant crossing, apply to Reinforced Concrete Structures in industrial and civil construction crane transport building materials and components.
1. Currently the main mode of speed – lifting mechanism :
Hoisting mechanism is the most important transmission mechanism of Tower Crane. Under the traditional timing method, overload requires low speed, low – speed and wide speed range; Lifting speed influences the whole performance directly. There are 3 principles to choose the speed control of hoisting mechanism: the first is stable and small impact; secondly, reliable and cheap; finally easy to be maintained.
1) Multi – speed motor pole – changing speed
The maximum weight of 6t or less keen competition in the small – medium tower crane, must control the cost strictly. Mainly based on variable – pole multi – speed motor speed, the scheme is simple, application is widely. Often achieved by 4/8/32 pole multi – speed motor.
2) Electromagnetic clutch gear reducer and Single – speed Wire – wound rotor motor with eddy current brake
To change the gear ratio by shifting electromagnetic clutch, Its advantages are running smoothly, the speed ratio range can be designed is wide. Its drawbacks are short Life, poor reliability, can’t change the clutch gear dynamically and the cost of decelerator is high.
3) Multi – speed Wire – wound rotor motor with general gear reducer and eddy current brake
This motor can connect resistor to get soft M-n characteristic, starting and braking are steady, its power can be bigger than the squirrel – cage motor used. This mode of speed regulation, the structure is simple, it is easy to maintenance, and the reliability is high.
Most of the 8~12t lifting mechanisms are using this speed control mode, but under this mode the motor has higher peak currents and impact when braking and shifting, Generally it is not used this mode of speed control for heavy lifting mechanism which the lifting weight is more than 8～12t.
4) Differential planetary gear speed reducer add dual-motors
This mode’s speed regulation ratio is big, can fully meet the requirements for overload with low speed and light load with high speed. And the reliability is high, particularly suitable for heavy lifting hoist body. But the structure is complex, need to design and produce non-standard parts, add dual-motors, the cost is high and the operation is complex.
5) VVVF AC speed regulation
VVVF AC speed regulation is the Most Advanced way, it’s widely applied in lifting Industry, its advantage is running long time in slow speed,Zero – speed brake,stability and safety.
2. AD300 series inverter
AD300 series inverter is a new generation,modular high – performance, phasor inverter. It has the following characteristics.
Perfect reliability of the design,all components meet industrial or military rank, professional production platform to make sure the reliability.
Compared with the starting mode of line frequency, the converter control can reduce mechanical vibrations and structure of the fake shock,save maintenance costs and make running stable.
3) H-VT HIGH W. CT-START
Using the High Performance flux vector control mode,to provide a stable and high output torque in low frequencies.