I. Introduction
The winch is also called a winch, and it is a device that is driven by a manpower or a mechanical power to drive a reel or a reel to complete the traction work. A simple lifting machine that lifts, levels, or inclines the weight vertically. Manual and electric two.
The electric winch is composed of a motor, a coupling, a brake, a gear box and a reel, and is mounted together on a rack. In the case of high lift, heavy loading and unloading, and heavy work, the speed control performance is required to be good, and in particular the empty hook can be rapidly lowered. Materials that are in place or sensitive to installation must be able to decrease in jog speed.
Winches include electric winches, construction hoists, and mini hoists. The main products are: JM electronically controlled large tonnage winches, JM electronically controlled low speed winches, JK electronically controlled high speed winches, JKL manual controlled quick release winches, and 2JKL manual double wins. Sliding hoists, electronically controlled hand-operated dual-use winches, JT speed hoists, etc., can only be used on the ground and can be modified for use on board. It is powered by an electric motor, and is equipped with an elastic coupling, a three-stage closed gear reduction box, and a tooth-coupled coupling to drive the reel. Electromagnetic brakes are used. The hoisting machine has high versatility, compact structure, small size, light weight, heavy lifting, and convenient use and transfer. It is widely used in the lifting, leveling and dragging of materials such as construction, water conservancy projects, forestry, mining and docks, and can also be used for modern electronic control. Automatic line equipment.
Second, the traditional winch control method
The working characteristics of the hoisting hoist are: slow starting speed, large torque, quick acceleration, smooth and accurate parking. The traditional speed regulation method is: using a wound rotor asynchronous motor, through the collector ring and carbon brush in the rotor loop in series of several resistance, the contactor to control the number of access resistance to control the speed.
However, there are the following disadvantages:
(1) The resistance of the series resistance is variable, and the speed change is jump-like, which makes the gears of the reducer, the sky wheel, the middle wheel, the material truck and the guide rail of the skew bridge be subjected to the impact force in the acceleration and deceleration operation phases, and the equipment is easy. Damage, the steel rope is easy to fatigue, resulting in a large amount of maintenance, maintenance costs increase.
(2) The series resistance has a small range of speed regulation, which makes the speed of the material truck abruptly, and it still has a relatively high speed when it is stopped after deceleration. This has a high requirement for the adjustment precision of the brake and the limit switch, and it is prone to off-site and off-track accidents and affect production. .
(3) The series resistance speed regulation makes most of the electric energy consumed in the resistor when starting and decelerating the material car. When the voltage of the electric motor decreases, the torque decreases and the slip rate increases. When the material is serious, the material car cannot start, and it is easy to start. An accident occurred.
(4) High energy consumption and low-speed mechanical properties are soft. Because the speed reduction is achieved through the external resistance of the rotor to consume energy, and the lower the speed, the softer the mechanical characteristics, the greater the proportion of energy consumed in the resistance, the most uneconomical, and the level of the grid voltage has a great influence on the speed.
Schedule: Comparison of Rotor Resistor Speed ​​Regulation and Variable Frequency Speed ​​Regulation
No.
project
Rotor series resistor speed regulation
Frequency
1
Addition and deceleration time
Acceleration and deceleration times change with load changes, and problems such as overspeed and overwinding of the deceleration section are likely to occur.
The acceleration and deceleration times do not change with the load, increasing the production efficiency.
2
Mechanical shock
Mechanical shock during acceleration and deceleration is large, and mechanical shock is large during crawling.
Smooth operation without mechanical shock
3
Grid impact
The impact on the power grid at start-up is 3 to 5 times of the rated current, and it also has a large impact on the power grid during deceleration and crawling.
The output current at start-up is about 1.2 times the rated current, and there is no output electric shock in the constant speed section, deceleration section, and creep section.
4
Slow crawl
Low-speed crawling mainly depends on the brake control and is unstable.
Stable at low speed, it can run smoothly at a low speed of 0.1M/S.
5
System energy saving
Without energy saving, the slip power on the resistor consumes a lot of energy.
Energy conservation is obvious, generally 20% to 40%.
6
Brake shoe wear
The brakes are frequent, the brakes are worn badly and the dust is large.
The brake wear is small, dust is reduced, and the work environment is good.
Third, AC80 vector converter winch control program
The Flextronics AC80 Vector Inverter uses the world's leading vector control algorithm to decompose the stator current of the motor into a torque current component and an excitation current component according to a coordinate transformation, thereby realizing accurate torque control. Compared with the V/F control algorithm, it has the advantages of good low-frequency torque characteristics, good dynamic response characteristics, and high speed control accuracy.
When the inverter has a 0.50Hz output, it has a high starting torque of more than 180% to ensure the motor torque at the time of flying start and low speed operation, and can be 100% torque in the speed range of 1:50 (1~50Hz). continue to operate. The speed regulation deviation is less than ±1%. And using a high-speed microprocessor and the latest generation of DSP to improve the response speed, in the lifting equipment to prevent "slip" is very effective, torque response time of about 0.1 seconds to reach 150% of the torque. When it falls, the inverter will be subjected to a higher potential energy release process. In order to ensure that the inverter does not overpower the pressure trip, a dynamic braking unit shall be added to ensure the normal operation of the inverter. When braking, the braking resistor and the active loss of the motor are combined into braking torque.
1) Traditional control of frequency conversion
1. Short circuit winding motor rotor windings, cancel the original string resistor speed control program; can also design the switching circuit, the original series resistor speed adjustment program as a backup program.
2. The motor brake system is independently powered and controlled by the inverter.
3, the original speed control device transformation, so that it can control the speed of the inverter.
4. Connect the inverter fault protection signal into the safety circuit.
The program is simple to invest in the transformation of simple equipment, can make good use of the original control system, and does not change the operating habits of workers. It is suitable for frequency conversion reform of the hoisting system of the control system.
2) Complete set of winch frequency conversion control system
1. AC80 vector frequency converter is used as the core of the speed control system and PLC is used as the core of the control system.
2, according to the configuration can be designed a variety of protection. And can flexibly customize the control system as needed.
According to the control requirements of the winch process and the signal from the signal system, the start, acceleration, deceleration, and stop of the winch are controlled, and the operation is stable and reliable.
(1) It realizes trip monitoring and position closed-loop control of winches, and has perfect depth and speed display and control functions.
(2) Realizing the vacuum and non-contact requirements of the main loop control device of the winch, adopting PLC control, simple hardware configuration, flexible software programming, convenient debugging and low maintenance. At the same time, it has good closed-loop performance.
(3) Improve the safety and reliability of the winch operation and the level of control technology, and play an important role in reducing equipment failure rate, increasing production efficiency, and reducing the labor intensity of operators.
(4) Security and interlocking functions. The safety circuit blocks the operating conditions of the winch. Only when the external equipment operates normally and has the driving conditions, the hoisting machine is allowed to operate. The safety circuit blocks all the heavy fault protection signals of the winch. Once the fault occurs, the winch immediately enters emergency braking; Failure can continue to run.
(5) Perfect comprehensive backup protection function.
(6) The use of photoelectric encoder to achieve the digital detection and control of the operating speed and position of the hoist, and improve the system control accuracy and reliability.
(7) The safety loops are double-redundant, with at least one software safety loop and one hardware safety loop.
(8) Failure of the PLC itself, such as "deadlock", "low battery voltage," "data transfer error," should be reliably detected and appropriate protective measures taken.
(9) There is a problem with one-way speed detection and depth detection, and under normal conditions on the other road, it should be possible to use the PLC for speed limit driving.
(10) Automatically send position signals, such as deceleration, stop, fixed point, over-roll signals, etc.; important points such as deceleration, over-rolling have two or more together.
(11) Speed ​​and depth are completely independent and compared with each other. The comparison time interval is not more than 1 second. If the speed and depth are not correct, necessary measures to prevent the accident from expanding will be taken immediately.
Fourth, the conclusion
With its excellent performance, Flextronics AC80 vector converter has greatly improved the stability and safety of traditional winches and reduced the maintenance of equipment. Weichuang Electric's customized control system for the winch incorporates numerous safety technologies and automatic control functions. It provides a complete set of electronic control solutions for the winch equipment manufacturers, and can also rejuvenate the old winches. Since its launch, it has won praise from users and also solved the problems of backward control of many mechanical manufacturers, and has achieved good social and economic benefits.
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