Electrification of the automotive repair shop and automation of electrical equipment of the bridge crane

Introduction

The basis of the economy of all industrial countries of the world is the electric power industry. The 20th century was a period of intensive development of this most important industry.

The transition from centralized management of the electricity industry to functioning within sovereign states has shown that the isolated operation of power systems cannot fully and reliably meet the needs of the economy and the population of electric energy.

The beginning of the 21st century can be described as years of certain stabilization of the operation of electrical systems. But electrical equipment is aging both mentally and physically, which requires the development and commissioning of new types of electrical equipment.

This diploma project is aimed at modernizing the power supply system of the car repair shop in order to increase the quality, reliability and safety of electric receivers. At the same time, part of the diploma project is also the modernization of electrical equipment of the bridge crane. At the end are economic calculations confirming the benefits of introducing new technologies into production.

Characteristics of the design object

1.1 Characteristics of the production area and mechanization facilities at the design site

The car repair shop is part of the Izhevsk Car Repair Plant.

The workshop is designed for the repair and manufacture of parts and assemblies of cars. The workshop is also designed to repair metal parts and metal connections.

The building of the workshop is reinforced concrete, the floor is concrete. AģB shop sizes =24ģ18м. The ground around the building is soup.

Natural and artificial lighting is provided in the workshop.

The mode of operation of the car repair shop is single-shift.

Automation of equipment

Cranes are called lifting devices that serve for vertical and horizontal movement of goods over short distances. According to the design features related to the purpose and working conditions, cranes are divided into bridge, portal, goat, tower, etc. In the workshops of electric machine building enterprises, bridge cranes were most widely used, with the help of which heavy blanks, parts and machine units are lifted or lowered, as well as their movement along and across the workshop. The type of bridge crane is mainly determined by the specifics of the workshop and its technology, however, crane equipment units, for example, lifting and moving mechanisms, are of the same type for various varieties of cranes.

The load of cranes, as a rule, varies widely: for lifting mechanisms - from 0.12 to 1; and for movement mechanisms - from 0.5 to 1 nominal value. It is also characteristic of cranes that their mechanisms operate in a re-short-term mode, when relatively long periods of work associated with the movement of goods alternate with small pauses for loading or unloading and fixing the load. Since multi-engine drive is used in cranes, and motors are connected through gears with lifting or moving mechanisms, they, like other elements of crane equipment, also work in a re-short-term mode with a large number of actuations per hour.

3.1 Patent search and literature review of progressive technologies.

1. Modern frequency converter for crane electric drive.

The main element of modern AC electric drives is a frequency converter. Despite the versatility of the current control algorithms and hardware implementation options for the converter, we can talk about typical solutions used by most manufacturers. In fact, unspoken standards for the structure of frequency converters and the functions they perform have been developed.

In general, it is possible to distinguish two main problems solved by an adjustable electric drive: control of the torque and speed of rotation of the engine. The need for torque control is dictated by the technical and technological requirements for the electric drive. For normal operation of the drive, it is necessary to limit the torque and current of the engine to the permissible values in the transient processes of starting, braking and application of load. For mechanisms experiencing significant overloads during operation, there is a need for continuous control of engine torque in order to limit dynamic impact loads .

Frequency converters with an intermediate DC link, built according to the rectifier-autonomous inverter scheme, received the greatest distribution. The principle of operation and application of such IF depends on the type of rectifier and autonomous inverter used.

Unmanaged rectifiers have become the most widespread. Made on the simplest and cheapest semiconductor devices - diodes, they are characterized by maximum simplicity and reliability, high efficiency, as well as a sufficiently high quality output voltage and harmonic composition of the current consumed from the network.

However, the uncontrollability of the energy conversion process does not allow the realization of the recovery modes required in many cases .

Controllable rectifiers, usually performed on low-frequency thyristors, are devoid of both the disadvantages and most of the advantages of diode rectifiers. They have high efficiency and reversibility in the direction of energy conversion and are usually used in conjunction with autonomous invertor miters to adjust the output current of the converter. Disadvantages of controlled rectifiers lie in increased level of pulsations of rectified voltage, in reduced value of power factor, which decreases in proportion to output voltage, and in one-way direction of output current. If it is necessary to ensure flow of rectified current in both directions, reversible tyrristor converters are used, which consist of two connected opposite-parallel thyristor rectifiers, one of which is designed to flow load current in forward direction and the other in reverse direction. This complicates and increases the cost of the converter.

The modern asynchronous drive is dynamically developing and is characterized by a wide range of proposed technical and traditimic solutions.

Frequency converters manufactured by OJSC "Electric Straightener"

During the last few years OJSC "Electric Straightener" together with STC of Electrical Engineering and Transport has been working on development of industrial production of converter for asynchronous AC electric drive. Converters are developed on the basis of domestic materials and components, including power devices manufactured by Electric Straightener OJSC - thyristors, diodes, voltage limiters, semiconductor resistors, IGBT - transistors.

Frequency converters for asynchronous electric drive are designed to ensure energy saving and increase application efficiency due to smooth speed control, as well as for installation in new facilities. In addition to energy saving, the use of frequency converters also provides optimization of technological processes and resource saving, elimination of starting currents of engines, mechanical impacts in load.

The frequency converter comprises the following main parts:

- input unit with over-voltage limitation;

- thyristor rectifier;

- DC link filter;

- PWM - inverter on IGBT - transistors;

- AC output filter.

International Rectifier Intelligent Power Modules

The modules of the new family, like their analogues, are designed to implement the control of three-phase contactless motors - asynchronous and contactless DC motors. therefore, they also include a three-phase inverter with a control and protection circuit. However, compared to analogues, they have a number of advantages.

Unlike their analogues, IR modules are available with several versions of the electrical circuit. Currently, two versions of the modules are mass-produced - A and B. Version A - a variant with open emitters of the lower inverter keys, version B - a variant with an embedded shunt in the zero potential bus circuit. This makes it possible to realize different combinations of current feedback and to choose the optimal one for a particular case.

The modules, as well as their analogues, include six IGBT crystals - transistors and anti-parallel ultra-fast diodes.

3.2 Development of structural diagram of the process.

The bridge crane operates in re-short-term mode. For a change, the crane carries from 10 to 15 different parts. The maximum load capacity of the crane is 10 tons.

The structural diagram for the bridge crane is a description of the process operations for moving the cargo in vertical and horizontal directions. To carry out the process, it is necessary to know exactly under what conditions the crane will work, in which room it will be located, at what height, under what lighting the personnel will work, etc. To lift, move and lower the load, it is necessary to select the engine of the required power, otherwise overheating and reloading may occur. The structural diagram of the process consists of the simplest elements, such as lowering an empty hook - securing the load on the hook - lifting the load - moving the load by a distance - lowering the load at the destination - removing the load from the hook.

Thus, the process of operation of the bridge crane is ensured.

3.6 Development of electrical schematic diagram.

Electric drive of bridge crane consists of asynchronous phase electric motor, power unit of thyristors with stator circuit, power unit of thyristors in rotor circuit.

Thyristor units operate in key mode. Thyristor is a controlled semiconductor device consisting of a four-layer silicon crystal with a p-p-p structure. External leads from extreme layers serve as cathode and anode, and output from one internal base area - as control electrode. If no current is applied to the control electrode, the thyristor is locked. If current is supplied to the control electrode, the thyristor under the anode voltage enters the conduction state.

The circuit remains on for as long as control pulses are applied. When the thyristors are removed, they are locked automatically after passing AC current in the power circuit through zero. Therefore, the trip time is half a period, i.e. 0.01 s, which is 1020 times less than that of conventional switches. Thyristors are connected opposite-parallel. If low-power pulses are supplied to the control electrodes, then one thyristor conducts current in the first half of the period and the second thyristor conducts current in the second half of the period.

Signal to control electrodes of stator and rotor thyristors is supplied from microcontroller circuit. Use the SA2 switch to specify the direction of movement and the speed of rise .

Electric drive comprises asynchronous motor with phase rotor. Engine acceleration takes place in three stages. And it is carried out using thyristors of the engine rotor circuit. By switching the thyristor unit of the rotor, the motor can be transferred from one artificial characteristic to another, depending on the electric current consumed by this motor. Thanks to this acceleration, the engine does not overheat.

The starting current limiters in this case are additional resistances in the R1R12 rotor circuit. Electric current consumption by asynchronous motor is controlled by means of alarm and feedback system via current transformers TA1, TA2. As a result of the operation of the feedback system in the crane electric drive, the semiconductor control system itself can limit the motor stator currents, depending on their value.

3.5 Selection of circuit elements.

The main elements of the circuit are the power thyristors VS1VS6, which are selected so that the maximum operating current of the thyristor exceeds the current of the electric drive motor. If this condition is not met, then the thyristors will overheat, and may even burn. In order to prevent thyristors from overheating during engine overloads, they are installed on special radiators - cooling fasteners, which are made of heat-capacitive metal.

Also, triode keys are widely used in the circuit, due to which the signal of thyristors supplied to the control electrodes is generated. The main elements of the circuit are transformers, which are necessary to obtain the required voltage level. The circuit contains a number of additional semiconductor devices, such as diodes, resistors and capacitors, etc.

Thus, the switching of the control circuit is based on a non-contact system, which allows improving the starting, operating and braking characteristics of the electric drive, as well as reducing the consumption of electric energy.

Feasibility study

4.1 Structure of the enterprise's energy economy

The main responsible for the energy economy at the Izhevsk plastics plant is the main energy engineer of the enterprise. He is responsible for all process equipment at the plant. The main energy of the enterprise is subordinated to both power engineers and masters of workshops and plots. Who, in turn, have workers subordinate. Such an energy organization allows the most efficient management of energy.

The supply department plays an important role in the enterprise, which serves to equip production with new parts and electrical devices in a timely manner.

4.2 Characteristics of the service object

The service object is a bridge crane. The bridge crane operates in re-short-term mode. For a change, the crane carries from 10 to 15 different parts. The maximum load capacity of the crane is 10 tons.

The main electrical equipment of the crane are engines (lifting and lowering engine, longitudinal movement engine and trolley transverse movement engine), and electrical equipment for controlling engines is also important. Since the lifting and lowering engine was modernized, and a new contactless control system for the bridge crane was delivered, an economic calculation for the newly installed equipment was given.

Conclusion

As a result of the designed power supply system of the automotive repair shop, the enterprise receives power from the power system through a 10 kV cable transmission line. As a point of receiving electricity, a transformer CTP with a transformer with a capacity of 250 kVdonbass A is used. All power from FTC is distributed at 0.4 kV via cable lines.

As a result, a scheme for distributing electricity to the workshop was determined - mixed. The workshop is powered by cable lines laid in sandy sand. To select the elements of the power supply scheme, short-circuit currents were calculated. Based on these calculations, protection devices were selected. The proposed power supply scheme meets the requirements of reliability, economy and safety.

Also, during the thesis project, changes were made to the electrical circuit of the cartridge center: the old motor of the main drive AO514 was replaced by the MKTV engine, which has the best technical indicators; elements of the control circuit were also removed: starters, circuit breakers, with the help of which the costs of repairing and maintaining electrical equipment were reduced.

This upgrade improves the reliability of the equipment, reduces maintenance and repair costs, and reduces energy consumption, which is an important criterion for the efficiency of the machine.. It has reduced operating costs for equipment maintenance, as well as the number of ongoing and major repairs, which ultimately affects the cost of production and the income of the enterprise.

During the completed diploma project, the costs related to the modernization of the fan electrical equipment were determined, the book value of the electrical equipment 45287 rubles was determined, the operating costs of the electrical equipment for the year were calculated, which amounted to 133855 rubles.