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Since the 1980s, the requirements of energy saving, consumption reduction and emission reduction have entered the agenda. In order to achieve this purpose, it is useful to change the frequency, voltage and speed of the motor, and also use hydraulic transmission to change the speed of the working machine. Energy conservation. The electrical control methods are: cascade thyristor, winding motors, such as DC motors, variable frequency motors, and frequency converters to change the speed of the motor. The mechanical transmission methods include: YOTC series speed-regulating hydraulic coupling, liquid-viscous speed governor, CST soft start, and magnetic coupling.


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DY electro-hydraulic coupling device

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New DY Electro-hydraulic Speed ​​Control Soft Start
New Technology for Transmission & Drive of Industrial High Power Machinery

  •      【Abstract】 This paper introduces the technology and application examples of variable speed hydraulic transmission and electro-hydraulic drive system. And compared with the mainstream traditional variable frequency soft start. Electro-hydraulic transmission & drive technology is a new type of drive technology imported from Germany after 2010. It has a short market promotion time and less experience in design and operation. Key words soft start, stepless speed regulation, flexible coupling, clutch, torque limit, overload protection, damping   Preface        Since the 1980s, the requirements of energy saving, consumption reduction and emission reduction have entered the agenda, in order to achieve this purpose , It is useful to change the frequency, voltage and speed of the motor, and it is also useful to change the speed of the working machine with hydraulic transmission, in order to achieve energy saving and emission reduction. The electrical control methods are: cascade thyristor, winding motors, such as DC motors, variable frequency motors, and frequency converters to change the speed of the motors. The mechanical transmission methods include: YOTC series speed-regulating hydraulic coupling, liquid-viscous speed governor, CST soft start, and magnetic coupling.
            1. YOTC series speed regulating hydraulic coupling
           After a long time of use and comparison, people have recognized the YOTC series of speed-regulating hydraulic couplings as a supporting product to solve the requirements of equipment soft start, power balance and power saving. The speed-regulating hydraulic coupling has been on this energy-saving stage since the 1980s. In the past 30 years, an average of about 3,000 speed-regulating hydraulic couplings have been put on the market each year for power, steel, coal, chemical industry, etc. On the machinery and equipment in the building materials, ports, transportation and other industries, it has made a great contribution to improving the operation technology of these equipment and saving energy.

     

       The working principle of YOTC series speed regulating hydraulic coupling:

       ●  The power transmission mode of YOTC coupling The power
           machine drives the oil supply pump to rotate, and the working fluid is pumped into the working chamber of the coupling. From the inner edge of the pump impeller to the outer edge, the liquid flow reaches the turbine through the gap between the two wheels. The role of the turbine is like a turbomachine. When the liquid flow in the channel between the turbine blades flows from the outer edge to the center, the liquid energy of the liquid flow is converted into the mechanical energy of the turbine. The flow begins the next cycle when it returns to the impeller. The rotating liquid flow in this way transmits the power of the motor to the working machine.
       ●  When the speed regulation mode of YOTC hydraulic coupling is
           started, the oil pump at the bottom of the coupling case is driven by the gear on the input shaft. The oil is injected into the working chamber after reaching the oil inlet through the water-cooled oil cooler.
           When the coupling is running, the oil overflows from the working chamber through the passage on the outer edge of the turbine and enters the conduit chamber. In the duct housing, there is a horizontally positioned and radially retractable duct (see drawing after). The catheter port extends into the catheter cavity, and the expansion and contraction of the catheter is controlled by the external electric actuator, and the radial position of the catheter port determines the thickness of the oil ring in the catheter cavity, which also determines the liquid filling volume in the working cavity. This determines the output speed. When the conduit extends into the rotating oil ring, the oil is drawn out from the conduit cavity, reducing the thickness of the oil ring, that is, the oil in the working cavity is drawn out, and the oil is discharged into the bottom of the tank for supply recycle. Conversely, when the conduit is retracted, the thickness of the oil ring increases, and more oil remains in the working chamber. In this way, the catheter lumen can be adjusted between two extreme positions of "full" and "evacuated" by using the external control device, so as to obtain the stepless speed change of the output shaft. It should be noted that the conduit port should face the rotation direction of the working oil.

     

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    Schematic diagram of YOT C structure (with photos)
       The advantages of YOTC series speed regulating hydraulic coupling:
           1. Improve the starting ability of squirrel cage motor, can use the peak torque of the motor as the starting torque; can be matched with high-voltage motors.
           2. Prevent power overload and protect the motor and working machine from being damaged due to overload.
           3. Reduce the vibration and shock during the start-up process, and realize the soft start of the working machine.
           4. Power balance and sequential starting can be carried out during the drive to reduce the impact current to the power grid.
           5. The starting time and safety of the working machine can be set according to the operation requirements. 
           6. It can be used for stepless speed regulation of the working machine, with high speed regulation accuracy (1%), and has a very significant power saving effect, with a power saving rate of 20% to 40%.
           7. Manual control, remote control and automatic control can be realized for the working machine, which is very convenient to operate.
           8. Not sensitive to ambient temperature, easy to dissipate heat.
           9. Simple and reliable structure, lower price than variable frequency speed control and CST speed governor, less running cost, no mechanical wear, can work in harsh environment, no special maintenance, long service life.

     

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       2. The upgraded version (DYC, DY) of computer control + speed-regulating hydraulic coupling (DYC, DY) mechatronics drive technology
           In high-power speed-regulating occasions and heavy-load equipment requiring soft starting, speed-regulating hydraulic couplings are used As a transmission is a good choice. First of all, it is popular because of its reliability, durability and low cost, but due to the inherent nonlinear characteristics of the liquid couple itself, it is difficult to meet the increasingly high requirements for speed regulation performance; secondly, many of the liquid couples are automated. Large-scale industrial and mining enterprises with high degree of high degree, these enterprises not only have higher and higher requirements for product quality and performance, but also have high requirements for product electrification and automatic program control. The hydraulic coupling itself is only a mechanical terminal product, which cannot meet these requirements, which affects the promotion of the liquid coupling.
           At present, the liquid couple electric control cabinets used in the market mainly use some conventional general-purpose instruments to realize the operation and monitoring of the liquid couple. This kind of electric control cabinet is too simple, and the electrical part is only passively serving the operation of the liquid couple, and it does not play a key role in the performance of the speed regulation without being organically combined with the liquid couple.
           To this end, the concept of electro-hydraulic (ie D&Y) mechatronics is adopted, and the special intelligent control system developed by today's microcomputer technology is organically combined with the speed-regulating liquid couple to form a more effective transmission and speed-regulating mechanism. That is, electro-hydraulic transmission equipment: it is an organic combination of a special speed-regulating fluid couple + special intelligent control equipment, which not only retains the good transmission characteristics of the fluid couple, but also makes the equipment intelligent and easier to control.
           The relationship between the output speed of the electro-hydraulic transmission equipment and the given value can be basically kept linear, and the stepless speed regulation can be realized. It not only overcomes the insufficiency of the nonlinear control of the liquid couple, but also brings into play the advantages of large transmission power, low cost, and simple maintenance and operation; at the same time, it realizes that all auxiliary systems of the electro-hydraulic transmission equipment can be automatically Start/stop, and implement local and remote centralized control.

           (1) Adhering to the concept of electromechanical integration. Combining modern computer technology and traditional liquid couples organically, the concept of electro-hydraulic transmission equipment is introduced, so as to meet the needs of soft start and stepless speed regulation of high-power equipment. Such as: for high-power fans, pumps, hoists, coal crushers, mining machinery, belt conveyors and other speed control soft start. In some high-power, heavy-load multi-drive conditions, it can also be easily combined into a multi-machine synchronous drive control system, such as: belt conveyor multi-machine drive (DYC).
           (2) The core of the electro-hydraulic transmission equipment control device is the intelligent controller programmed in C language, which is a fuzzy control algorithm that combines artificial intelligence and PID algorithm specifically for the characteristics of the liquid couple, and realizes the effective control of the liquid couple. All control functions are integrated into the general box, the operation is clear at a glance, concise and practical; in some occasions with high automation requirements, it can also easily realize networking and remote monitoring.
     
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    In-situ universal box touch screen display interface   Remote computer configuration software interface

           • The new DYC electro-hydraulic flexible transmission & drive technology was introduced from Germany at the end of the last century and after nearly 20 years of absorption and transformation, it can be used as a common technology for a new generation of mechanical transmission & drive systems;
           • It has five functions: clutch, flexible coupling Shaft, soft start, stepless speed regulation, overload protection  ;
           • One-stop solution to the key problems of mechanical transmission & drive: heavy load soft start, dynamic load hazards, torque limit, stepless speed regulation ;
           • Compared with traditional mechanical Transmission & drive technology increases efficiency by more than 30% (energy saving, consumption reduction, emission reduction);
           • It is a simpler, cheaper and more convenient mechatronics integration technology.
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       It has been successfully used in:
           •  Diesel electro-hydraulic drive device of chain bucket dredger (soft start, stepless speed regulation)
           • Drive adopts diesel engine + DY electro-hydraulic drive + reducer (drive by belt conveyor for coal transportation) Similar) 
           • From the diesel engine through 1# reduction box + pulley set + 2# reduction box + chain bucket, the speed is reduced from 1200rpm to 4rpm. This is a typical hybrid mechanical drive combination of belt drive, chain drive and gear drive. The bucket excavates sand at a frequency of 8~10″. The dynamic load fluctuation density is high, the impact is large, and the problems caused by alternating torsional vibration are very serious. Extreme. After adopting the new electro-hydraulic drive technology, the problems of belt slippage, gear wear, spindle breakage, and black smoke from diesel engine have been successfully solved, and the energy saving effect is remarkable.
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           •  Application of multi-point drive control (Guizhou Liupanshui Hongguo Coal Mine Transfer Station) 
           •  DY electro-hydraulic dual-drive intelligent dynamic control system for 8 00kw*2 belt conveyor 
    • Features        : soft start, multi-drive power balance, stepless speed regulation , flexible coupling, clutch, overload protection
           •  Supporting high-power water pump (vertical pump, horizontal pump) 
           •  Speed ​​regulation and energy saving system 
           • Laigang Wide and Heavy Plate Factory 
           • 750kw pump 
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           •  Formosa Plastics Hejing Steel Plant 2800kw dust removal fan (750rpm) 
           •  Soft start, speed regulation and energy saving system 
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           •  Can be used in tube mill, vertical mill, rotary kiln
           • With clutch, soft start, flexible coupling, stepless speed regulation, overload protection, damping functions
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           • Widely used in a variety of mechanical equipment...
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       3. Computer control + speed-regulating hydraulic coupling upgraded version (DYC, DY) mechatronic drive technology

     

     

    Project/Product Hydraulic speed control soft start Variable frequency speed control soft start
    1. Performance   1. Adjust the filling volume to make stepless speed regulation of the working machine.
      2. Soft start the system, the starting time can be very long, and there is no limit on the number of starts.
      3. High overload capacity, can use the peak torque of the motor, and strong starting ability under heavy load.
      4. Multi-machine drive can balance power and automatically control speed and current.
      1. Change the frequency of the motor and steplessly regulate the speed of the motor.
      2. Soft start the system, and the starting time can be very long.
      3. The overload capacity is poor. To increase the overload coefficient, the inverter must be upgraded, and the cost will be hundreds of thousands of yuan per level.
      4. Adjust the motor frequency to balance the power.
    2. Price low investment    The overall investment is high (dedicated air-conditioning, ventilation, and dust-free electrical rooms are also required) 
    3. Reliability   High reliability
      1. Even if the control system fails, the device can still be manually controlled to run
      2. Simple structure, no bypass system required
      Low reliability
      1. If any link in the complex control system of the inverter fails, the system will not be able to operate.
      2. The structure is complex and the reliability of use in high altitude areas is lower. Although the reliability of the electrical components used in current frequency converters has been improved compared to the past, the large number of electrical components (several thousands) in large frequency converters makes their overall reliability much lower. Therefore, there must be a speed-regulating or fixed-speed bypass control backup system for important applications.
    4. Power fluctuations   Voltage fluctuations do not affect the operation of the coupling

       When the power supply voltage drops below 80% of the rated voltage due to various reasons, the self-protection of the electronic inverter will cut off the motor power supply. Even if the voltage drop time is only 100 microseconds, the protection will operate, and the electronic inverter can be equipped with automatic restart facilities (additional investment is required) .

       Even so, it will take at least 5-10 seconds for the motor to restart. During this time, the motor stops without power, which can cause a major shock to the process system and can lead to a safe shutdown of the plant. In smaller power supply systems, voltage drops are prone to occur.

    5. Harmonic influence   No harmonic effects    The electronic inverter generates current and voltage high-order harmonics in the power supply system. The amount of high-order harmonics generated depends on the size of the inverter. The type of inverter and the short-circuit capacity of the power supply system are used. For low power supply capacity, the power capacity is small. system, the interference of harmonics is very obvious. These disturbances include:
      ● Additional losses in the motor and supply transformer (therefore, the motor must be chosen to be larger, typically around 12%).
      ● Motors and transformers generate extra noise (2-5db[A]).
      ●In addition to the normal driving torque, the motor will generate pulse torque (these torsional vibrations will also be transmitted to the working machine, increasing the mechanical impact and loss).
      ● Affected by harmonics, additional energy loss occurs in the entire power supply system.
      ● Have adverse effects on other electrical equipment and people, such as computers, controllers, etc.
      ● Capacitor banks, voltage transformers, ballasts or capacitors in the power supply system may cause harmonic problems and increase energy consumption.
      ● may lead to the installation of harmonic filters to reduce the impact of harmonic generation (additional investment and maintenance)

    6. Power factor,

    efficiency

    High power factor, efficiency is 97~98%

       The power factor is low and the efficiency is low, only 90~94%. The efficiency data given by the inverter is often misleading. First, it is difficult (and very expensive) to measure its efficiency by carrying out a load test. Second, there are harmonics. The additional losses in the motor, transformer and overall system are not taken into account, and thirdly, the energy consumption of the air conditioning cooling system and the harmonic filter is not taken into account.

       Inverter efficiency at different speeds: (Robincon perfect non-harmonic series inverter produced by Siemens)

    Inverter efficiency%

    Rotating speed%

    20

    40

    60

    80

    100

    Torque %

    20

    74.6~85.9

    84.9~94.8

    89.2~94.2

    91.5~95.3

    92.8~96

    40

    84.5~91.0

    91~95.5

    93.2~96.1

    94.8~96.6

    95.6~96.9

    60

    88.3~92.5

    93.2~95.7

    95~96.4

    95.9~96.8

    96.3~97

    80

    93~90.3

    94.3~95.7

    95.7~96.4

    96.2~96.9

    96.6~96.8

    100

    91.4~93.2

    94.8~96.7

    95.9~95.7

    96.4~96.5

    96.5~96.6

     

    7. Matching motor

    Ordinary squirrel cage motor

       A special frequency conversion motor must be used. Compared with ordinary asynchronous motors, the rated current is 8~10% larger, and the temperature rise is increased by 20%.

    8. Transformer requirements

    High voltage and low voltage motors available

       If low-voltage electronic inverters are used (because medium and high-voltage inverters are expensive and have low reliability), a special transformer must be used (resulting in additional investment and maintenance). If a high-voltage motor is used, usually connected to a low-voltage inverter, a special step-up transformer needs to be added between the output of the inverter and the speed-regulating motor. The capacity of the transformer must be large, because it must operate at a frequency lower than 50HZ. The following operates and in order to prevent magnetic saturation at low frequency start-up.

    9. Area

    smaller

       The electrical switch room of the high-power inverter takes up a lot of space, resulting in increased investment.

    10. Electric cabinet cooling system

    No additional cooling required

       The heat loss generated in the inverter box must be discharged. The heat loss is about 5% of the rated power, which has nothing to do with the actual motor load and speed. For high-power inverters, this loss is very significant, and the cooling air must be cooled The fan is filtered and blown into the chassis for cooling. The maximum allowable cooling air temperature is 40°C, which means that there must be a large amount of circulating air, and the energy consumption of air conditioning and cooling air is greater than the loss of the frequency converter itself.

       In addition, air-water heat exchangers can also be used, but this solution has high investment and high maintenance costs.

    11. Electric cabinet noise

    none

       The inverter is very noisy. Large frequency converters with noise levels exceeding 85D db(A).

    12. Equipment maintenance

    General Mechanical Maintenance

       Troubleshooting and repairs are time-consuming and expensive, and in order to solve the problem, the supplier's experts must be consulted.

    13. Spare parts

    Inexpensive mechanical spare parts

       A large number of spare parts are required, which can only be supplied by the manufacturing plant. Due to the rapid development of electronic technology, some components are outdated after a few years and difficult to purchase.

    14. Packaging and transportation

    Ordinary equipment packaging

       The cost of experiment, packaging, transportation, installation and start-up of the factory is very high, and these costs are generally not considered when comparing equipment prices.

    15. Extra cables

    no need

       If a low-voltage motor is used with a low-voltage inverter, the connection cables between the step-down transformer and the input end of the inverter and between the output end of the inverter and the speed-regulating motor must be connected in parallel (4 cables are required for a rated current of 1000A). ), the wiring of these cables on the motor requires a special junction box. When the motor is repaired, all these wirings must be removed, which is difficult. Because of the large diameter of the cable, the heat losses in the cable are considerable, affecting the overall efficiency.

    16. Lubrication system

    Fluid coupling with lubricating system to provide lubricating oil for motor and working machine bearings

       Large high-speed motors usually use sliding bearings instead of rolling bearings. Motor sliding bearings and pump bearings must be regularly maintained. These sliding bearings need oil lubrication and a separate lubrication system must be installed (additional cost and maintenance).

    17. Frequency conversion method

    no such requirement

       There are basically two types of frequency converters: voltage source frequency converters and current source frequency converters. Voltage source inverters are inefficient and generate more harmonics than current source inverters. If the motor is not connected to the output terminal of the current source inverter, and the inverter is unloaded, it can neither run and test, nor test or find faults, because these cannot be carried out under no-load conditions, if there is no motor at that time or the motor has not Ready or unable to operate due to factory reasons, the above limitations will cause significant inconvenience.

    18. Control system

    Use a simple local control system. With local/remote/automatic/manual 

       The frequency converter needs to arrange additional control and monitoring positions in the switchgear room where the frequency converter is placed, which means that additional cables, relays, internal interlocks and starting sequence devices must be added to meet the control requirements and thus increase the cost and failure rate. and maintenance.

    19. Explosion-proof requirements

    The speed regulating hydraulic coupling has the underground safety mark certificate

       To meet the explosion-proof requirements requires a large cost and is more difficult to achieve.

     

            From the above comparison, it can be seen that the hydraulic speed control soft start and the variable frequency speed control soft start can achieve soft start and multi-drive power balance. However, from the comparison between points 2 and 19, it can be seen that the use of variable frequency speed control devices is more complicated. , There are more unfavorable factors, the service life is shorter, and the management and operation costs are higher.


       4. Energy efficiency comparison between variable frequency speed control soft start and hydraulic speed control soft start  DY electro-hydraulic energy-saving drive system, rated transmission efficiency of 97~98.5%, no electromagnetic interference, electrostatic interference; using power frequency power supply, and asynchronous energy saving The motor is matched to form an ultra-efficient and energy-saving drive system, with higher energy-saving efficiency. Frequency conversion speed regulation adopts frequency conversion motor. Compared with ordinary asynchronous motor, the current is increased by 8~10% and the temperature rise is increased by 20%; In addition, in order to improve the reliability and stability of the inverter, it is also necessary to configure a large number of peripheral auxiliary appliances: transformers, power circuit breakers, AC contactors, filters, reactors, braking resistors, etc. These electrical configurations consume >5% power. It can be seen that compared with the DY electro-hydraulic energy-saving drive system, the variable frequency drive system has greater comprehensive energy consumption and lower efficiency under rated operating conditions.
           

     

     

       5. DY electro-hydraulic drive device also has excellent flexible transmission characteristics.
           DY electro-hydraulic flexible transmission & drive technology not only has excellent drive control performance, but also can play the characteristics of hydraulic flexible transmission. Operating characteristics can solve the hazards of dynamic loads (torsional vibration, resonance, overload) and reduce operation and maintenance costs; it can reduce the configuration redundancy of transmission & drive systems and reduce investment costs.
           1. Change the resonance speed of the shaft system. The larger the torsion angle based on the torque (that is, the smaller the stiffness), the smaller the impact torque and the lower the resonance speed. The torsional stiffness of the hydraulic coupling can be adjusted, and it can operate at a suitable torsion angle (slip) according to the alternating torque of the load to reduce the generation of resonance.
           2. Reduce the torsional vibration of the shaft system, especially suitable for working conditions with frequent load changes. The hydraulic coupling device uses 30~40# turbine oil as the transmission medium, with large viscous damping (increasing friction damping), which can rapidly attenuate vibration, convert the energy impact of torsional vibration into heat, and consume it through heat dissipation , so that It can reduce the mechanical impact wear of the drive shaft, enhance reliability and prolong service life.
           3. When the equipment is accidentally overloaded, it will often cause damage to the transmission or other parts. If the hydraulic coupling device is used in the transmission shaft system, the clutch (semi-clutch) function can be used to interrupt the transmission torque or limit the transmission of torque, which can play a role in safety protection.
           4. The DY electro-hydraulic drive can be clutched, which can enable the motor and the working machine to start separately. The characteristics of the clutch, whether it is no-load or heavy-load, can start the motor with no-load (allowing the motor to start at full voltage), shorten the start-up time, and reduce the starting current (no need to specially consider the "big horse-drawn trolley" problem of heavy-load starting) . The motor starts first, and after reaching the rated speed, the working machine is soft-started by adjusting the hydraulic coupling to slowly load: 0~100% stepless speed regulation operation. The traditional frequency conversion is a conventional V/f control, and the voltage drop of the motor increases relatively with the decrease of the motor speed, which leads to the insufficient excitation of the motor, so that the motor cannot obtain enough rotational force. When the load is heavy, it needs to be equipped with more than 1.5 times the motor margin, otherwise it may not be strong enough to start.  

           Through the above comprehensive comparison, the new DYC electro-hydraulic speed control soft start device technology can replace the current traditional variable frequency drive and CST drive, with better performance, lower equipment investment costs, higher operating efficiency, and lower operating and maintenance costs. It is a new technology that is more suitable for transmission & drive of industrial machinery and equipment.
     

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