light industry

一、preface
With the industrial production of crane speed performance requirements continuously improve, commonly used in traditional method of crane speed make on-site maintenance, speed control system of the high failure rate, and poor speed control system of integrated technical indicators, has been unable to meet the special requirements of industrial production. David chuangfei ECF500 vector inverter used in hoisting industry has got good results, has been widely used in the industry. The current domestic tower crane hoisting mechanism of several main control mode are introduced in this paper. The pointing out the advantages and disadvantages of various ways and the scope of application; for rope 4 maximum lifting weight is less than or equal to the 6T small and medium tower proposed using AC variable frequency speed regulation method, is given by using Yi Chong Fei ECF500 vector frequency converter to realize the perfect solution. Tower crane for the construction of the template technology for research and development, applicable to the construction of reinforced concrete structure of the industrial and civil construction materials and components of the hoisting and lifting.

二、At present, the main speed regulation mode of domestic hoisting mechanism
Lifting mechanism is the most important transmission mechanism of tower crane. At present, the traditional speed control mode requires heavy load and low speed, light load and high speed range, and the speed regulation mode of lifting mechanism directly affects the performance of the whole machine. Lifting mechanism to choose the principle of choice has three: first, to be stable, the impact of small; second to the economy and reliability; three is to facilitate maintenance.
1, multi speed motor variable speed
Rope 4 maximum lifting weight is less than or equal to the 6T fierce competition in the small and medium tower, control cost strictly, the domestic to multi speed motor variable speed regulating pole mainly, scheme is simple, application is wide, often used at the multispeed motor to achieve.
2, ordinary reducer with eddy current braking of the multi speed winding rotor motor
Multi speed motor drive ordinary single speed ratio reducer and disadvantage relative to large multi speed motor shift shock, the eddy current brake speed belt wound rotor motor can be resistor string get softer Mn characteristic, from braking and gear shifting is relatively stable, slow positioning speed, the power can be than squirrel cage motor with large. This speed control method is simple in structure, easy to maintain and high reliability. At present, the heat dissipation problem of the eddy current brake winding rotor motor is solved, and the reliability of the speed regulation mode is greatly improved.
At home 8 ~ 12t lifting mechanism mostly adopts the speed adjustment way, but this kind of motor has brake and shift is still greater peak current and impact, the electrical control system is complex, 16t above the large tonnage from 3, frequency control
Variable frequency speed regulation is the most advanced mode of AC speed regulation. With the gradual decline in the price of the international frequency converter, the application of frequency control technology is more and more widely. The tower crane hoisting mechanism has been used for many years, the effect is good, but not wide. It has the advantages of slow positioning speed can run for a long time, to achieve zero speed braking, stable operation and no impact, can prolong the life of the structure and transmission parts, of wire rope row rope and a life of great benefit, and safety of the tower crane is improved. 

三、Scheme of frequency converter in tower crane hoisting mechanism
Early tower crane hoisting mechanism in application of frequency conversion technology in Japan Yaskawa inverter based, mainly used in the shaft of machine, and rope 4 maximum lifting weight is less than or equal to the 6T small and medium tower fierce competition, cost control strictly, so the application of frequency converter is very little. With the development of power electronic technology, domestic inverter technology is becoming more and more mature, price performance advantage obviously, is widely used in small and medium-sized tower crane has become a reality.
1, Yi chuangfei inverter introduction
ECF500 series inverter Shenzhen Yi Chong fly Electrical Co., Ltd. launched on behalf of the future direction of transducer development of a new generation of module of high performance inverter. Compared with the traditional sense of V / F converter, in order to meet the requirements of customers of different performance and function demand aspect. It is not through a number of series of products to achieve (thereby increasing the additional manufacturing, sales, use, maintenance costs), but in the customer needs the reasonable segmentation based, for modular design, through a combination of single series products of multi module, create a custom tailored platform. Is a few of the real magnetic flux vector technology in the inverter.
Excellent no velocity vector control strategy which has a faster dynamic response, current limiting technology and hardware optimization design of advanced, can guarantee under the frequent fluctuation of load and inverter without tripping by the series inverter. And has the following characteristics:
A, reliability
Perfect reliability design scheme: such as redundant design, reduce the amount of design and so on, all components are used in industrial or military level; professional production platform, so as to ensure the reliability of the whole machine.
B, soft start
Compared to the power frequency starting mode, the inverter control can reduce the vibration of the mechanical part and the impact of the structure, to save the cost of maintenance, and stable operation.
C, high starting torque
Using high performance flux vector control mode, the low frequency segment provides stable high output torque.
2, process introduction
In the small tower crane typical specifications qtz315 tower crane, a wide range of applications; 2 times the rate of major technical indicators: maximum liter weight 3T, lifting speed 52/26/5.5m/min and lifting mechanism 15/15/5.5kW at the multipole motor, gear ratio I=12.5 drum diameter of 300mm.
3, parameter calculation
Crane variable frequency drive system consists of a main controller and a potentiometer for the given input, through the use of frequency modulation speed control equipment, load measuring and controlling instrument, limit position switch, brake etc. with, to control the crane hoisting mechanism. AC asynchronous motor, braking, reversible operation and control.
Equipment selection parameters: moving pulley 2 magnification, lifting mechanism 18.5kW 4 pole asynchronous squirrel cage motor, reducer ratio I=31.5; drum diameter 300mm, that is, I=31.5, R=D/2=150mm=0.15m, Nn=1450,, Pn=18.5kW.
A, the calculation of the maximum lifting weight
Pn=2* PI *Nn*Tn/60*1000
Tn=: Pn*1000*60/2* * Nn=18.5*1000*60/2 Pi Pi *1450=121.9Nm
The theory of lifting weight is: F=2*Tn*I*/R*10000=2*121.9*31.5/0.15*10000=5.1198T
Considering the transmission efficiency is 0.64, the maximum lifting weight is: Fmax=0.64*F=0.64*5.1198=3.28T
Compared with the requirements of the maximum lifting weight is 1.1 times the insurance coefficient, basically in line with the requirements of the.
B, maximum lifting speed calculation
Vmax= *D*Nn/2*I= Pi Pi *0.3*1450/2*31.5=21.7 m/min
According to the known, frequency conversion mode, motor maximum lifting speed is reduced a lot, mainly considering the cost saving, to be competitive in the market, design related hardware cost estimate to optimization; by shortening the time of startup and in place, empty hook is higher than 50Hz operation and so on many kinds of coordination methods, the practice does not obviously feel slow down.
4, performance characteristics
The advanced modern AC variable frequency speed control technology technical reconstruction of the tower crane electric drive system, the crane can realize stable operation, improve operational efficiency, improve the overload operation, eliminate the impact of brake, reduce electrical maintenance, reduce the power consumption, improve power deficiency factor can be achieved good results. Also has over current, over voltage, under voltage and input lack phase protection, and over temperature transducer, overload, overspeed, overheated brake unit, I / O fault protection, motor fault protection, frequency conversion method has significant characteristics are as follows:
A, wide speed range, can achieve precise control of the positioning requirements of the job;
B, soft start, soft stop function reduces the impact of mechanical transmission, can significantly improve the bearing capacity of the steel structure, and the service life of the crane is prolonged;
C, high integration component and high reliability low voltage electrical equipment, effectively solve the complicated problem of the original electrical system wiring, not only reduce the system failure probability, but also easy to maintain;
D, the motor at zero speed, the full torque output, even if the brakes loose or failure, there will be no heavy fall, to ensure that the system is safe and reliable;
E, with a fast dynamic response, will not slip hook and really achieve zero speed cross function;
F, special load weight measurement and control instrument with the corresponding software, lifting speed can be changed with the change of load weight from the switch, to achieve "light load fast, heavy load slow" job requirements;
G, the system used frequency converter, with automatic energy-saving operation mode, can greatly improve the system power factor and the efficiency of the whole machine, energy saving effect is remarkable, the average power saving rate can reach more than 20%.

四、Concluding remarks
So far, the design of speed sensorless vector frequency control tower crane test machine has been six months, the whole equipment is running well, and accept orders more than taiwan.
At present, most of the tower crane is used in the most of the speed regulation, although it is the development direction, but it is still limited by the cost and so on. The above similar without increasing the transducer selection, appropriate to sacrifice speed method, the cost of frequency conversion stepless speed regulation with eddy current brake speed around the rotor pole changing speed difference is not big, performance, but greatly improved, visible significance is great.