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Product Details
New DY Electro-Hydraulic Speed-Controlled Soft Starter
A new technology for transmission and drive in high-power industrial machinery
- [Abstract] This article introduces the technology and application examples of speed-regulating hydraulic transmissions and electro-hydraulic drive systems, and compares them with mainstream conventional variable-frequency soft-start systems. The electro-hydraulic transmission and drive technology is a new type of drive technology that was introduced from Germany after 2010 and subsequently adapted and developed through local absorption and innovation. It has been on the market for only a relatively short period, and thus there is still limited design and operational experience available.
[ Keywords 】 Soft start, stepless speed regulation, flexible coupling, clutch, torque limitation, overload protection, damping
Preface
Since the 1980s, requirements for energy conservation, consumption reduction, and emission reduction have been placed on the agenda. To achieve these goals, some approaches involve adjusting the frequency, voltage, and speed of electric motors, while others utilize hydrodynamic transmissions to vary the operating machinery’s speed, thereby promoting energy savings and emission reductions. Among the electrical control methods are cascade-controlled thyristors, wound-rotor motors—such as DC motors and variable-frequency motors—and the use of inverters to adjust motor speeds. Mechanical transmission methods include the YOTC series speed-regulating hydraulic couplings, hydroviscous speed regulators, CST soft starters, and magnetic couplings.I. YOTC Series Speed-Regulating Hydraulic Couplings
After extensive comparative testing, the YOTC series of speed-regulating hydraulic couplings have been widely recognized as an ideal complementary product for addressing the needs of soft starting, power balancing, and energy conservation in various equipment. Since the 1980s, speed-regulating hydraulic couplings have been playing a key role in energy-saving applications. Over the past three decades, an average of approximately 3,000 units of these couplings have been introduced annually into the market, finding application in mechanical equipment across industries such as power generation, iron and steel, coal mining, chemical processing, building materials, ports, and transportation. These couplings have made significant contributions to improving operational processes and enhancing energy efficiency in these industries.Working Principle of the YOTC Series Speed-Regulating Hydraulic Coupler:
● Power transmission method of the YOTC coupler
The prime mover drives the oil pump to rotate, and the working fluid is pumped into the coupling’s working cavity. Like a centrifugal pump, the pump impeller imparts kinetic energy and potential energy to the oil within the working cavity, causing the oil to rush outward from the inner edge of the impeller toward its outer edge. The oil flow then passes through the gap between the two wheels and reaches the turbine. The turbine functions much like a turbomachinery: as the oil flow moves from the outer edge toward the center through the channels between the turbine blades, it converts the fluid’s kinetic energy into mechanical energy for the turbine. When the oil flow returns to the pump impeller, it initiates the next cycle. In this way, the rotating oil flow transmits the prime mover’s power to the driven machine.
● Speed-regulating method of YOTC hydraulic couplings
When the equipment is started, the oil pump—driven by the gear on the input shaft—pumps oil from the bottom of the coupling housing. The oil then flows through a water-cooled oil cooler and, upon reaching the inlet port, is injected into the working chamber.
When the coupling is operating, the hydraulic fluid overflows from the working cavity through channels along the outer edge of the turbine and enters the guide tube cavity. Inside the guide tube housing, there is a horizontally positioned guide tube that can extend and retract radially (see the accompanying diagram for details). The opening of the guide tube extends into the guide tube cavity, and its extension and retraction are controlled by an external electric actuator. The radial position of the guide tube’s opening determines the thickness of the oil ring within the guide tube cavity, which in turn governs the amount of fluid filling the working cavity—and thus controls the output rotational speed. When the guide tube extends into the rotating oil ring, it draws oil out of the guide tube cavity, reducing the thickness of the oil ring. This action removes fluid from the working cavity and directs it to the bottom of the housing for recirculation. Conversely, when the guide tube retracts, the thickness of the oil ring increases, allowing more fluid to remain in the working cavity. In this way, by using an external control device to adjust the guide tube cavity between two extreme positions—“fully filled” and “empty”—the output shaft achieves stepless speed variation. It is important to note that the opening of the guide tube must face the direction of rotation of the working oil.
Youth Olympic Games C Structure Schematic Diagram (with illustration)Advantages of the YOTC series speed-regulating hydraulic couplings:
1. Improving the starting capability of squirrel-cage motors allows the motor’s peak torque to be utilized as the starting torque; it can also be used in conjunction with high-voltage motors.
2. Prevent power overload and protect the motor and working machinery from damage due to overload.
3, Reduce vibration and shock during the startup process, enabling soft starting of the working machine.
4. The drive system can perform power balancing and sequential starting, reducing inrush currents that impact the power grid.
5. The startup time of the working machine can be set according to operational requirements for safety.
6. The working machine features stepless speed regulation with high speed-control accuracy (1%), delivering remarkably significant energy savings—energy consumption can be reduced by 20% to 40%.
7. The working machine can be controlled manually, remotely, and automatically, making operation extremely convenient.
8. Insensitive to ambient temperature and easy to dissipate heat.
9. It features a simple and reliable structure, is more affordable than variable-frequency drives and CST speed controllers, incurs lower operating costs, has no mechanical wear, can operate in harsh environments, requires no special maintenance, and boasts a long service life.
II. An upgraded electromechanical integration drive technology featuring computer control plus a speed-regulating hydraulic coupling (DYC, DY).
In high-power speed-regulation applications and equipment requiring soft starting under heavy loads, using a speed-regulating hydraulic coupling as a transmission device is an excellent choice. First, it is widely favored for its reliability, durability, and low cost. However, due to the inherently nonlinear characteristics of hydraulic couplings themselves, it becomes increasingly difficult to meet the ever-higher demands for speed-regulation performance. Second, many of the customers facing hydraulic couplings are large-scale industrial and mining enterprises with highly advanced levels of automation. These enterprises not only have increasingly stringent requirements for product quality and performance but also place great emphasis on the electrification, automation, and computerized control of their products. Since the hydraulic coupling itself is merely a mechanical end-product, it cannot satisfy these comprehensive requirements, thereby hindering the wider adoption of hydraulic couplings.
Currently, the hydraulic coupling electronic control cabinets used in the market primarily rely on conventional, general-purpose instruments to perform operation and monitoring of the hydraulic couplings. Such electronic control cabinets are overly simplistic; their electrical components merely serve passively to support the operation of the hydraulic couplings without being integrally linked with them, thus failing to play a critical role in fully realizing the speed-regulating performance.
To this end, we have adopted the mechatronic concept of electro-hydraulic (i.e., D&Y) integration and developed a specialized intelligent control system leveraging today’s microcomputer technology. This system is organically combined with speed-regulating hydraulic couplings to create a more efficient transmission and speed-control mechanism—the electro-hydraulic transmission equipment. This equipment represents an organic combination of a specialized speed-regulating hydraulic coupling and a dedicated intelligent control unit. It not only retains the excellent transmission characteristics of the hydraulic coupling but also endows the equipment with intelligent features, making it easier to operate and control.
The output speed of the electro-hydraulic transmission device maintains a roughly linear relationship with the given command, enabling stepless speed regulation. This system not only overcomes the nonlinearity inherent in hydraulic couplings but also leverages their advantages of high transmission power, low cost, and simple maintenance and operation. At the same time, all auxiliary systems of the electro-hydraulic transmission device can be automatically started and stopped according to process requirements, and centralized control—both local and remote—is implemented.
(1) Adhering to the principle of integrating mechanical and electrical technologies, we have organically combined modern computer technology with traditional hydraulic couplings to introduce the concept of electro-hydraulic transmission equipment. This approach effectively meets the demands for soft starting and stepless speed regulation in high-power equipment—for example, providing smooth start-up and adjustable speed control for high-power fans, pumps, elevators, coal crushers, mining machinery, belt conveyors, and more. In certain high-power, heavy-load multi-drive applications, these systems can also be conveniently integrated into multi-machine synchronous drive control systems, such as the multi-machine drive unit for belt conveyors (DYC).
(2) At the heart of the electro-hydraulic transmission equipment control system is an intelligent controller programmed in C language. Specifically tailored to the characteristics of fluid couplings, this controller employs a fuzzy control algorithm that combines artificial intelligence with PID algorithms, thereby achieving effective control of the fluid coupling. All control functions are integrated into a universal enclosure, making operation straightforward, concise, and highly practical. In applications with high automation requirements, it is also easy to network the system and enable remote monitoring.
On-site universal box touchscreen display interface Remote computer configuration software interface
• The new DYC electro-hydraulic flexible transmission and drive technology, introduced from Germany at the end of the last century and refined through nearly 20 years of absorption and adaptation, can serve as a common technology for the next-generation mechanical transmission and drive systems.
• Equipped with five major functions: Clutch, flexible coupling, soft start, stepless speed regulation, overload protection ；
• One-stop solution for key challenges in mechanical transmission & drive systems: Heavy-load soft start, dynamic load hazards, torque limitation, stepless speed regulation ；
• Compared to traditional mechanical transmission and drive technologies, it achieves more than 30% efficiency improvement (energy saving, reduced consumption, and lower emissions);
• It is a more simple, cheaper, and easier-to-use mechatronic integration technology.
Has been successfully used for:
• Diesel-electro-hydraulic drive system for chain bucket dredgers (Soft start, stepless speed regulation)
• The drive system employs a diesel engine + DY electro-hydraulic drive + gearbox (similar to the drive system used for coal-carrying belt conveyors).
• From the diesel engine, the rotational speed is reduced from 1200 rpm to 4 rpm via a No. 1 gearbox + belt pulley assembly + No. 2 gearbox + chain-driven bucket. This is a typical hybrid mechanical drive system incorporating belt transmission, chain transmission, and gear transmission. The bucket scoops sand at a frequency of 8 to 10 inches per cycle, resulting in high fluctuation density and significant impact in dynamic loads. The problems caused by alternating torsional vibrations are particularly severe. After adopting a new electro-hydraulic drive technology, these issues have been successfully resolved. Belt slippage, gear wear, spindle fracture, and black smoke from the diesel engine. The issue has significant energy-saving effects.• Applications of multi-point drive control (Honggu Coal Transfer and Loading Station, Liupanshui, Guizhou)
• 8 00 kW × 2 Belt Conveyor DY Electro-Hydraulic Dual-Drive Intelligent Dynamic Control System
• Features: soft start, multi-drive power balancing, stepless speed regulation, flexible coupling, clutch, and overload protection.• High-power pumps (vertical pumps, horizontal pumps) as accessories
• Speed-control energy-saving system
• Laigang Wide and Thick Plate Mill
• 750kW pump• Taiplast Ha Tinh Steel Plant 2800kW dust removal fan (750 rpm)
• Soft start and speed control energy-saving system unified• Suitable for tube mills, vertical mills, and rotary kilns.
• Equipped with clutch, soft start, flexible coupling, stepless speed regulation, overload protection, and damping functions.• Widely used in a wide variety of mechanical equipment...
III. An upgraded electromechanical integration drive technology featuring computer control plus speed-regulating hydraulic couplers (DYC, DY).
Project/Product Hydraulic speed-regulating soft start Variable-frequency speed control soft start 1. Performance 1. Adjusting the liquid filling level enables stepless speed regulation of the working mechanism.
2. The system features soft start, with a potentially very long start-up duration and no limit on the number of start-ups.
3. High overload capacity, capable of utilizing the motor’s peak torque and featuring strong heavy-load starting capability.
4. Multi-motor drive enables power balancing and allows for automatic control of speed and current.1. By changing the motor frequency, the motor speed can be continuously adjusted.
2. The system features soft starting, and the start-up duration can be quite long.
3. The overload capacity is poor; to increase the overload factor, we would have to upgrade the frequency converter to a higher class, with each upgrade adding several hundred thousand yuan to the cost.
4. Adjusting the motor frequency allows for power balancing.2. Price Low investment High overall investment (requiring dedicated air-conditioned, ventilated, and dust-free electrical rooms) 3. Reliability High reliability
1. Even if the control system fails, the device can still be operated manually.
2. Simple structure, no bypass system required.Low reliability
1. If any component in the inverter’s complex control system fails, the system will become inoperable.
2. The structure is complex, and reliability is lower in high-altitude regions. Although the reliability of electrical components used in current variable-frequency drives has improved compared to the past, the large number of electrical components—thousands—in a typical large-scale VFD significantly reduces its overall reliability. Therefore, for critical applications, it is essential to have a backup system with either speed-control or fixed-speed bypass functionality.4. Power fluctuations Voltage fluctuations do not affect the operation of the coupler. When the supply voltage drops below 80% of its rated value for any reason, the electronic frequency converter’s built-in protection system will cut off the motor’s power supply. Even if the voltage dip lasts only 100 microseconds, the protection mechanism will still activate. The electronic frequency converter can be equipped with an automatic restart feature (at an additional cost). Nevertheless, it will take at least 5 to 10 seconds for the motor to restart. During this period, the motor will come to a complete stop due to the loss of power, potentially causing significant disturbances to the process system and even triggering a safe shutdown of the entire plant. In smaller power systems, voltage dips are particularly likely to occur. 5. Harmonic Impact No harmonic interference Electronic variable-frequency drives generate higher-order harmonics in the power supply system. The magnitude of these harmonics depends on the size of the drive, the type of drive used, and the short-circuit capacity of the power supply system. In systems with low power supply capacity—i.e., systems with relatively small electrical capacity—the harmonic interference is particularly noticeable. These interferences include:
● Additional losses are generated in the motor and the power supply transformer (therefore, the motor must be selected slightly larger—typically by about 12%).
● Motors and transformers generate additional noise (2–5 dB[A]).
● In addition to generating normal driving torque, the motor will also produce pulse torque (these torsional vibrations will be transmitted to the working machine, increasing mechanical impact and wear).
● Harmonics cause additional energy losses throughout the power supply system.
● Causes adverse effects on other electrical equipment and people, such as computers and controllers.
● Capacitor banks, voltage transformers, ballasts, or capacitors in power supply systems may generate harmonic problems, increasing energy consumption.
● May necessitate the installation of harmonic filters to mitigate the effects of harmonics (which will increase additional investment and maintenance costs).6. Power factor, efficiency High power factor, with an efficiency of 97–98%. The power factor is low, and the efficiency is only 90% to 94%. The efficiency data provided by variable-frequency drives often mislead people. First, it is extremely difficult—and costly—to determine their actual efficiency through load tests. Second, the additional losses caused by harmonics in motors, transformers, and the entire system are not taken into account. Third, the energy consumption of air-conditioning cooling systems and harmonic filters is also overlooked. Efficiency of variable-frequency drives at different speeds: (Siemens’ Robicon Perfect Harmony series VFDs) 
7. Matching motor Standard squirrel-cage motor A dedicated variable-frequency motor must be used; under rated conditions, its current is 8% to 10% higher than that of a conventional asynchronous motor, and its temperature rise increases by 20%. 8. Voltage Regulation Requirements Available with high-voltage and low-voltage motors If a low-voltage electronic variable-frequency drive is used (since medium- and high-voltage VFDs are expensive and have lower reliability), a special step-up transformer must be employed, which leads to additional investment, increased floor space requirements, and higher maintenance demands. If a high-voltage motor is used—typically in conjunction with a low-voltage VFD—a specially designed step-up transformer must be installed between the VFD’s output and the speed-regulated motor. This transformer must have a very large capacity, as it needs to operate at frequencies below 50 Hz and to prevent magnetic saturation during low-frequency starting. 9. Land area Smaller The electrical switchgear room for high-power inverters requires a large amount of space, leading to increased investment. 10. Electrical cabinet cooling system No additional cooling required The heat loss generated inside the inverter enclosure must be dissipated. This heat loss amounts to approximately 5% of the rated power and is independent of the actual motor load and speed. For high-power inverters, this loss can be particularly significant. The cooling air must be filtered by a cooling fan and then blown into the enclosure to create a cooled zone. The maximum allowable temperature of the cooling air is 40°C, which means that a large volume of air circulation is required. As a result, the energy consumption for air conditioning and cooling fans can exceed the inverter’s own power losses. Additionally, an air-water heat exchanger could also be used; however, this solution involves high initial investment and high maintenance costs. 11. Electrical cabinet noise None The inverter generates significant noise. For large-scale inverters, the noise level exceeds 85 dB(A). 12. Equipment Maintenance General Mechanical Maintenance Fault diagnosis and repair are extremely time-consuming and costly; to resolve the issue, it is essential to consult with the supplier’s experts. 13. Spare parts Low-cost mechanical spare parts A large number of spare parts are required, and only the manufacturer can supply these parts. Due to the rapid pace of advancements in electronic technology, some components become obsolete after just a few years, making them difficult to procure. 14. Packaging and Transportation Standard equipment packaging The costs associated with factory testing, packaging, transportation, installation, and commissioning are extremely high. These costs are typically not factored into comparisons of equipment prices—nor are the expenses for training maintenance personnel and organizing product documentation. 15. Extra cable No need If a low-voltage motor is used in conjunction with a low-voltage variable-frequency drive, the connecting cables between the step-down transformer and the input terminal of the VFD, as well as between the output terminal of the VFD and the speed-regulated motor, must be wired in parallel—specifically, four cables are required for a rated current of 1000 A. These cables must be connected to a special junction box on the motor. During motor maintenance, all these connections must be disconnected, a task that presents certain challenges. Due to the large diameter of the cables, thermal losses within the cables are considerable, which in turn affects overall efficiency. 16. Lubrication System The hydraulic coupling is equipped with a lubrication system that provides lubricating oil for the bearings of both the motor and the working machine. Large high-speed motors typically use sliding bearings rather than rolling bearings. The sliding bearings in motors and pump bearings require regular maintenance. These sliding bearings need to be lubricated with oil, necessitating the installation of a separate lubrication system (which incurs additional costs and maintenance requirements). 17. Variable Frequency Method No such requirement. There are basically two types of inverters: voltage-source inverters and current-source inverters. Voltage-source inverters have lower efficiency and generate more higher-order harmonics than current-source inverters. If no motor is connected to the output of a current-source inverter, and the inverter is running at no load, it cannot be operated or tested under no-load conditions, nor can faults be diagnosed or identified—since such tests and troubleshooting cannot be performed when the inverter is running at no load. If, at that time, there is no motor present, the motor is not yet ready, or for some factory-related reason the motor cannot be started, the aforementioned limitations will cause significant inconvenience. 18. Control System Adopts a simple on-site control system. Features on-site/remote/automatic/manual modes. The frequency converter requires an additional space for control and monitoring devices in the switchgear room where the frequency converter is installed. This means that extra cables, relays, internal interlocks, and starting sequence devices must be added to meet the control requirements, thereby increasing costs, failure rates, and maintenance workload. 19. Explosion-proof requirements Speed-regulating hydraulic couplings all have underground safety certification. Meeting explosion-proof requirements involves significant cost expenditures and is relatively difficult to achieve. As can be seen from the comparison above, both hydraulic speed-regulating soft starters and variable-frequency drive (VFD) soft starters can achieve soft starting and multi-drive power balance. However, as shown in the comparison from point 2 to point 19, using a VFD is more complex, involves more adverse factors, has a shorter service life, and incurs higher management and operating costs.
IV. Energy Efficiency Comparison Between Variable-Frequency Speed Control Soft Start and Hydraulic Speed Control Soft Start
DY electro-hydraulic energy-saving drive system boasts a rated transmission efficiency of 97% to 98.5%, with no electromagnetic or electrostatic interference. Powered by power frequency electricity and paired with an asynchronous energy-saving motor, this system forms an ultra-high-efficiency, energy-saving drive system that achieves even greater energy savings. Variable-frequency speed control uses a variable-frequency motor. At rated conditions, the current increases by 8% to 10% compared to that of a conventional asynchronous motor, and the temperature rise increases by 20%. For every 1 kVA of inverter capacity, heat generation ranges from 50 W to 60 W, resulting in additional energy consumption compared to using a power supply at industrial frequency. In addition, to enhance the reliability and stability of inverter operation, a large number of peripheral auxiliary electrical devices must also be configured, including transformers, power circuit breakers, AC contactors, filters, reactors, braking resistors, and others. The power consumption of these electrical components exceeds 5%. As can be seen, compared to the DY electro-hydraulic energy-saving drive system, the variable-frequency drive system exhibits higher overall energy consumption and lower efficiency under rated operating conditions.
5. The DY electro-hydraulic drive unit also features excellent flexible transmission characteristics.
DY electro-hydraulic flexible transmission and drive technology not only boasts excellent drive control performance but also leverages the unique advantages of hydraulic flexible transmission. By modifying the start-up and operational characteristics of the driven machinery, it can effectively mitigate the hazards associated with dynamic loads (such as torsional vibrations, resonance, and overloads), thereby reducing operation and maintenance costs. Additionally, this technology can minimize redundancy in the configuration of the transmission and drive system, lowering overall investment costs.
1. By altering the resonant speed of the shaft system, the larger the torsional angle based on torque (i.e., the lower the stiffness), the smaller the impact torque and the lower the resonant speed. The torsional stiffness of a hydraulic coupling can be adjusted, enabling it to operate at an appropriate torsional angle (slip) in response to the alternating torque of the load, thereby reducing the occurrence of resonance.
2. Reduces torsional vibrations in the shaft system, making it particularly suitable for operating conditions with frequent and significant load variations. The hydraulic coupling device uses turbine oil of grade 30–40 as the transmission medium, providing substantial viscous damping (increasing frictional damping). It can rapidly dampen vibrations, converting the energy of torsional vibrations into heat and dissipating it through thermal radiation. This can reduce mechanical impact and wear in the transmission shaft system, enhance reliability, and extend service life.
3. When equipment experiences an unexpected overload during operation, it often leads to damage to the transmission system or other mechanical components. If a hydraulic coupling is used in the drive shaft system, Utilize its clutch (half-clutch) function. By interrupting the transmission torque or limiting the transfer of torque, a safety protection function can be achieved.
4. The DY electro-hydraulic drive features a clutch that allows the motor and the working machine to be started separately. Thanks to this clutch’s unique characteristics, the motor can be started under no-load or heavy-load conditions—enabling full-voltage starting of the motor without any special considerations. This significantly shortens the startup time and reduces the inrush current (eliminating the need to worry about the “using a big horse to pull a small cart” issue typically associated with heavy-load starts). First, the motor is started; once it reaches its rated speed, the hydraulic coupling is adjusted to gradually apply load, providing a smooth soft start for the working machine—with stepless speed regulation ranging from 0% to 100%. Traditional variable-frequency drives employ conventional V/f control, in which the voltage drop across the motor increases relatively as the motor speed decreases. This, in turn, leads to insufficient excitation, causing the motor to fail to generate adequate rotational torque. Under heavy loads, it becomes necessary to select a motor with a margin of at least 1.5 times the rated capacity; otherwise, the motor may lack sufficient power during startup.
Through the comprehensive comparison outlined above, the new DYC electro-hydraulic speed-regulating soft-start device technology can replace current conventional variable-frequency drives and CST drives. It boasts superior performance, lower equipment investment costs, higher operational efficiency, and lower operation and maintenance expenses—making it a more suitable new technology for the transmission and drive of industrial machinery and equipment.
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