УДК 621.87 Rahimli I.N., Mirzaliyev E.Kh.
Rahimli I.N.
associate professor Azerbaijan State Oil and Industry University (Baku, Azerbaijan)
Mirzaliyev E.Kh.
master
Azerbaijan State Oil and Industry University (Baku, Azerbaijan)
DEVELOPMENT OF ELECTRIC DRIVE FOR CRANE LIFTING MECHANISMS
Аннотация: among the mechanisms used in industrial enterprises, crane mechanisms are one of the most common. This article provides an overview of overhead cranes, which are the main types of crane mechanisms. For the optimal choice of electric drive, the basic requirements were taken into account. The systems "Voltage regulator - DC motor" and "Frequency converter -asynchronous squirrel-cage motor" for controlling the electric drive of a crane are considered. The main advantages of this system are shown.
Ключевые слова: frequency converter, overhead cranes, voltage, rotation speed, mechanical characteristics.
Crane mechanisms are divided into several types depending on the methods of use. Examples of these types are overhead cranes, portal cranes, and tower cranes. Bridge cranes are very common in production. The structure of overhead cranes is quite complex. Overhead cranes mainly have three main mechanisms: lifting mechanism, bridge mechanism and trolley mechanism. These mechanisms are controlled by the operator. It should be noted that these mechanisms are used consistently. That is, it is impossible to use two or more mechanisms at the same time. There are requirements
for electric drive of each mechanism of overhead cranes. Examples of these requirements are the ability to change the rotation frequency of the engines in a wide range, the need for the rigidity of the mechanical characteristics of the drive, to minimize the time of transition processes, etc. can be shown. Compliance with these requirements is very important.
Currently, overhead cranes are controlled by frequency converters. One frequency converter can be used to control three or more drives. Zero protection is implemented in the mechanism to prevent any mishaps that may occur. Zero protection is a system that restricts the operation of the crane if the operator leaves the cabin and when the voltage is restored, if the operation of the crane is interrupted due to the loss of mains voltage for any reason. Overhead cranes are a lifting mechanism used to shift loads horizontally and vertically over short distances. Figure 1 shows the design of an overhead crane. According to the lifting capacity, overhead cranes are conventionally divided into (10-15) ton medium, (10-25) ton cranes and larger (50) ton cranes [1-3].
Figure 1. Overhead crane.
Choosing the type of current for crane electrical equipment, the technical possibility of drive, investment, the cost of operating costs, the mass and dimensions of the equipment are important for its reliability and ease of service. It is possible to
apply an electric drive system and various motors for the transmission of crane mechanisms. Their selection depends on the lifting of the load, the nominal speed of the movement, the adjustment of the speed of the transfer in the required range, the difficulty of the mechanical characteristic, the number of connections in 1 hour, etc. is defined as dependent. Nowadays, cranes mainly use a simple system of electric drive, in which the motors are fed from an alternating current network or a constant current regulated by a tripping resistor. Electric drives with short-circuited rotor asynchronous motors are used in crane mechanisms with low lifting power (10-15 kW) operating in light mode. The most commonly used in cranes are electric drives with an asynchronous motor with a step-by-step adjustable phase rotor by changing the resistance in the rotor circuit. These types of electric drives do not provide the necessary reliable work in low copies. Therefore, the angle copy is more reliable adjustable direct current motors are used. Constant current motors are used to raise and lower low-mass loads at high speed.
To choose the right electric drive system, you need to know what mechanism it is used for. In order to optimally choose the electric drive, it is necessary to meet the basic requirements so that it is simple and inexpensive, and it can fulfill the requirements of the mechanical operation indicators [4].
Lifting, lowering and shifting loads of electric drives of cranes must meet many requirements. These requirements are:
1. Engine rotation frequency can be adjusted in many limits:
Common faucets have 4:1 and special faucets have 10:1 and more. According to these signs, it is necessary to control the speed of the engine at a low speed when the crane is loaded, and at a high speed when the crane is unloaded, so that the production percentage of the unit is high. It is necessary to operate at a low speed so that the load needs to be placed anywhere. Let the cost of the impact in the parking lot be low, and let the operator's job be easy.
2. In order to achieve rigidity in the mechanical characteristics of the electric drive, the provision of regulation should be carried out under the condition that the low speed is almost independent of the load.
3. Limitation of the momentum to certain values in the shortest period of time in transition processes is due to weak shocks in strong mechanical drives, which is related to the sliding of the moving mechanisms.
4. Reversal and operation of the electric drive in engine start and brake mode. "Voltage regulator - DC motor" and "Frequency converter - Short-circuited
rotor asynchronous motor" systems are used for the control of crane electric drives. The fact that asynchronous motors with a short-circuited rotor are more reliable and cheaper than direct current motors has led to the use of the last mentioned system. The application of this system is distinguished by the following advantages:
- Engine starting and braking processes are performed fluently according to the linear law;
- Engine start-up and braking times are smoothly adjustable between fractions of a second and 50 minutes;
- As a result of smooth implementation of transition processes, the life of mechanical parts is extended;
- The engine is protected from overloading, phase failure and other emergency
modes;
- As a result of speed regulation and fluent transition processes, technological processes are controlled effectively [5-7].
It should be noted that crane electric drives with 3 or more electric motors can be controlled by one frequency converter. Application of such a system requires compliance with some requirements as well as reducing capital investment.
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