L48A1 Mast Section realize the speed regulation of medium and large tower cranes
Medium and large tower crane hoisting speed regulation mode:
L48A1 Mast Section
http://www.towercranesupply.com/product/l48a1-mast-section-for-tower-crane-masts
1. Ordinary reducer
Compared with the squirrel cage motor, the multi-speed wound rotor motor with eddy current braking has the disadvantage of large impact on shifting. The multi-speed wound rotor motor with eddy current braking acquires soft M-N characteristics through series resistance, and the starting braking and gear switching is more stable, with slow emplacement speed. The rate can be larger than the cage motor, generally up to 55-75kW. This kind of speed regulating mode has simple structure, easy maintenance and high reliability.
After repeated exploration, the motor matching plant successfully solved the problem of heat dissipation of eddy current braking and wound rotor motor several years ago, which greatly improved the reliability of this speed regulation mode. At present, domestic 8-12T lifting mechanism mostly adopts this speed regulation mode. However, the motor braking and gear shifting still have a large peak current and impact, and the electrical control system is relatively complex, so the large tonnage lifting mechanism above 16T is generally not suitable to adopt this speed regulation mode.
2. Electromagnetic clutch
The advantages of the gearbox and the single-speed wound rotor motor with eddy current braking are that the operation ratio is stable and the speed ratio can be designed to be larger. Its shortcomings are more, first of all, the electromagnetic clutch is generally used in domestic machine tool products, short life, poor reliability; Secondly, the clutch gear can not be dynamically changed in the air, or it will slip, which is very dangerous; Finally, the cost of reducer is higher.
3. Differential planetary reducer
The solar wheel with double motor planetary reducer is driven by one motor, the planetary frame is driven by another motor through planetary deceleration, and the inner gear ring of outer orbit is fixed on the lifting reel. This is the construction of a differential planetary reducer. After the planetary system is determined as a certain appropriate parameter, the speed of the drum depends on the speed and steering of the two motors, which are fast in the same direction and slow in the opposite direction. If it is a single speed motor, each motor has three states of forward rotation, reverse and stop matching with the other motor, so there are many speed gears. If you use a multi-speed motor, you have more speed gear. This is the principle of differential speed regulation. The motor can be combined with squirrel cage or frequency conversion and squirrel cage. For small tonnage, the frequency conversion and squirrel cage can be combined for large tonnage. This way of speed regulation ratio is large, can fully meet the requirements of heavy load low speed, light load high speed, and high reliability, especially suitable for large tonnage lifting mechanism.
4. Variable frequency speed regulation
Frequency conversion speed regulation is the most advanced mode of ac speed regulation. With the gradual decrease of the price of international frequency converter, frequency control technology is more and more widely used. Domestic tower crane lifting mechanism has been used for many years, with good results, but not widely used. Its advantages are slow emplacement speed can run for a long time, achieve zero speed braking, smooth operation without impact, can prolong the life of structure and transmission parts, is of great benefit to wire rope and life, at the same time improve the safety of tower crane.
But, the price of imported frequency converter is more expensive, domestic frequency converter is not very stable. Once there is a problem with the frequency converter, it can't be repaired. Most of them can only be replaced. Variable frequency speed regulation due to the high cost, the general small and medium tonnage lifting mechanism less application, large tonnage is more. Speed adjustment in small and medium tonnage large area use, only waiting for the rise of domestic frequency converter.
L48A1 Mast Section
http://www.towercranesupply.com/product/l48a1-mast-section-for-tower-crane-masts
