Application status and development trend of frequency conversion technology in tower crane industry


2019-03-28 10:13

1. Types and characteristics of control technology for the hoisting mechanism of tower cranes

1. Pole-changing speed regulation type This type is mainly used in small and medium-sized tower cranes. Usually a squirrel-cage three-speed motor is used, and the working speed of high and low gears and the slow in-position speed of the first gear are obtained by changing the number of poles. It can meet the basic requirements of tower cranes for speed regulation. The advantage is that the mechanism is simplified, but the disadvantage is that the impact is large when shifting gears, the speed regulation range is about 1:8, and it cannot maintain low-speed operation for a long time.


2. Two-speed wound rotor series resistance speed regulation type This type is mainly used in large and medium tower cranes. Usually the construction machinery industry uses a two-speed wound rotor motor. This motor has two pole pairs, and the speed is regulated by series resistance and changing electrodes. Usually five-speed control is used, the advantage is that the operation is relatively stable and the impact on the mechanism is small.


3. Double motor drive speed regulation type Mainly used in large and medium tower cranes. Usually two wound motors are used for driving. Two motors are connected by gears (speed ratio is 1:2), one is used for driving and the other is used for braking. It is also possible to use two multi-speed cage motors for driving, or a speed-regulated winding motor and a cage-type motor for each speed-regulated drive, which can obtain different speed-regulation characteristics. The advantage of dual-motor drive speed regulation is that the hoisting mechanism can adjust the speed during the load movement, and can achieve airborne descent at the maximum speed, thereby improving the construction efficiency, realizing the accurate positioning of the hoisting load, stable work, large speed regulation range, up to One to forty. However, the mechanism is relatively complex, and its transmission components need to be specially designed and manufactured.


4. Variable frequency speed regulation This is the most advanced drive scheme at present, suitable for various types of tower cranes. The frequency converter is used to drive the variable frequency motor, which has a large range of speed regulation, and the speed can be adjusted according to the scene, which is more flexible. At the same time, it has a strong protective effect on the motor protection, and the impact on the mechanism is small. And this kind of hoisting mechanism also has the ability to adjust the speed during the load movement, can use the maximum speed to drop the air, the hoisting load can be accurately positioned, the work is stable, the production efficiency is high, the adjustable speed range is large, and the mechanism is relatively simple.


2. Difficulties encountered in the popularization of frequency converters in the industry At present, frequency converters are only used by a few manufacturers, and more and more are used in large and medium-sized tower cranes. As far as the entire tower crane industry is concerned, frequency converters are not widely used.


There are still some difficulties in the popularization of frequency converters, which are embodied in the following aspects:
1. In terms of cost, its price is relatively high, which increases the cost of equipment.
2. Unfamiliar, customers are afraid when using new technologies and new products.
3. Tower crane maintenance personnel are unfamiliar with frequency converters, and subjectively believe that after using frequency converters, they cannot be repaired, will not be repaired, or are more difficult to maintain, and have a psychology of resistance.
4. In order to achieve the best effect, the variable frequency tower crane needs to adjust the parameters according to the working conditions, so it is more complicated than the ordinary tower crane.


3. Status quo of domestic inverters There are few domestic inverter manufacturers that have large-scale applications on tower cranes, such as Sine, Megmeet and so on. Now with the development of frequency conversion technology, more practitioners in the construction machinery industry have an increasing understanding of frequency converters and frequency conversion tower cranes, and everyone has formed a consensus that the use of frequency converters is the trend of the times and cannot be reversed.


At present, there are many manufacturers of domestic inverters, and the inverter industry is also uneven and mixed. Technical capabilities, R&D level, and industrial concentration all need to be optimized, and the tower crane industry is more willing to trust foreign brands. With the industrialization, informatization and urbanization environment, the development of my country's inverter industry will have a huge market and development space.


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