Application of energy feedback of the hottest freq

The application of frequency converter + energy feedback in crane system (2)

structure introduction

the application of frequency conversion and speed regulation technology in the transmission mechanism of tower crane has been in China for nearly 10 years. Although some successful application experience has been obtained, and many frequency conversion hoisting mechanisms are now in normal operation on the construction site, compared with other industries, the application of frequency conversion and speed regulation technology in tower crane is far from reaching its due level, There are both cost and technology reasons

in terms of technology, the typical schemes currently adopted at home and abroad are similar, with the following differences:

(1) the brands of frequency converters are different, and their control circuits are different

(2) the system is open-loop (without PG) or closed-loop (with PG)

(3) the form of mechanical structure is different: L-shaped layout п Type layout or one-way layout, etc

(4) the types of reducers are different, such as cylindrical gear reducers or planetary reducers; It is constant speed ratio or variable speed ratio, etc

in terms of transmission control technology, the above differences do not involve the change of control mode, but the slow change of temperature drop. They are all typical modes of using a frequency converter to control a motor for speed regulation, which can also be called conventional frequency conversion lifting mechanism. Among all these conventional frequency conversion mechanisms, the frequency conversion lifting mechanism assembled by Liebherr on ec-h tower crane has the most prominent characteristics. It adopts 250V motor and its matching frequency converter, and is equipped with reducer with variable speed ratio and L-type layout. The scheme has good lifting speed characteristics, and its disadvantages are high system cost and poor component versatility

2. Design points of conventional variable frequency lifting mechanism

(1) verification of motor pole number and power

when the basic parameters of the lifting mechanism (such as maximum lifting weight, maximum working speed, etc.) are given, the pole number and power of the motor should be determined and calculated, The key points of its design are:

a) the output speed of the motor should be less than 3000 R/min (the working speed limit of the starting level from the inspection operation of the reducer input materials)

b) the maximum working frequency of the system should be small to change the volume of the sealed working cavity to achieve oil absorption and pressure at 100Hz (the higher the frequency, the greater the loss power of the motor, which will destroy the constant power characteristics, and the lifting capacity will be greatly reduced without practical application value)

c) the rated torque of the motor is used to check the maximum lifting capacity (considering the total transmission ratio, efficiency, magnification, etc.)

d) the rated power of the motor is used to check the lifting capacity at high speed (considering the total transmission ratio, efficiency, magnification, etc., if the frequency is close to 100Hz, the effective power should be reduced by 10 ~ 15%

when selecting motor power, the reduction ratio of reducer, motor power and pole number can be basically determined according to the above conditions