As a Tower Crane Manufacturer, share with you. The lifting mechanism is the
most important transmission mechanism of a tower crane. It requires heavy load
at low speed, light load at high speed, and a large speed range. The advantages
and disadvantages of the speed regulation method of the lifting mechanism
directly affect the performance of the whole machine. Small and medium-sized
tower cranes with a maximum lifting capacity of 4 tons or less are fiercely
competitive, and their cost control is strict. In China, multi-speed motors are mainly used for variable pole speed regulation. The scheme is simple and can
still meet the work needs. Flat Top Tower Cranes of 8t and 8t need better speed
regulation performance. There are many speed regulation methods. There are three
selection principles: first, they must be stable and the impact is small;
secondly, they must be economical and reliable, in line with national
Flat Top Tower Cranes
1.1 Gear reducer for electromagnetic clutch shifting and single speed winding rotor motor with eddy current brake
This speed regulation method is widely used in German LIEBHERR tower cranes. China has been using it for decades, but it has gradually faded out. It changes the speed ratio of the reducer by shifting the electromagnetic clutch, and obtains the soft characteristics and the slow in-position speed by the resistance of the single-speed wound rotor motor with eddy current braking. Its advantage is that the running efficiency is stable and the speed regulation ratio can be designed to be larger. It has many disadvantages. First, the electromagnetic clutch is generally made of domestic machine tools, which has a short life and poor reliability. Second, the clutch gear cannot be dynamically changed in the air, otherwise it will slide down, which is very dangerous. Third, the cost of the reducer is higher.
If our country can develop a more economical electromagnetic clutch with a long life, it will still be a better way of speed regulation. Many users are used to using electromagnetic clutches.
1.2 Ordinary reducer plus multi-speed wound rotor motor with eddy current brake
Changing the electromagnetic clutch shift of the previous method to a multi-speed motor-driven ordinary single-speed ratio reducer is the idea of this method.
Compared with the shortcomings of the multi-speed squirrel cage motor, the gear shifting impact is large. The multi-speed wound rotor motor with eddy current brake can obtain a soft Mn characteristic by series resistance. (It should not be used for a long time in place), the power can be larger than that of squirrel cage motor, generally it can reach 55 ~ 75kW. This speed regulation method has simple structure, easy maintenance and high reliability. After repeated exploration, the motor supporting factory successfully solved the heat dissipation problem of the eddy current brake wound rotor motor a few years ago, which greatly improved the reliability of this speed regulation method.
1.3 Differential planetary reducer plus dual motors
The sun gear of the planetary reducer is driven by one motor, the planet carrier is driven by another motor through planetary deceleration, and the inner ring gear of the outer track is fixed on the lifting drum. This is the structure of the differential planetary reducer.
Our company also has 12 T Top Kit Tower Crane for sale, welcome to consult.