variable speed fluid coupling
Daimler used these throughout their range of luxury cars, until switching to automatic gearboxes with the 1958 Majestic. Now, before the suppliers of other technologies become upset, I must point out that the most if not the same benefits are available from many other Variable Speed Drive (VSD) technologies such as fluid couplings, hydrostatic drives, continuously variable transmissions, DC … 2. with variable pumps, the control system is defective 3. rotational speed and/or delivery excessive 1. The volume of gas delivered from the fan changes as a function of the movement of the damper. Methods of fan volume control are as follows: Variable Speed Drive. The simplest rectifiers use diodes to convert AC to DC by allowing current flow in one direction only. This is not generally a concern at the voltages (three-phase @ ≈ 400V) used in most plastics processing but motors may need improved windings or controls if higher voltages are used. This is primarily done inside the VSD unit. {\displaystyle d} The turbine is connected to the input shaft of the transmission. These must be filtered out to reduce magnetic noise, reduce motor vibration and prevent them being fed back into the system. A fluid coupling consists of three components, plus the hydraulic fluid: The driving turbine, known as the 'pump', (or driving torus[a]) is rotated by the prime mover, which is typically an internal combustion engine or electric motor. Installation and start-up went well and the coupling is performing as expected demonstrating significant benefits (vibration reduction) over the Voith hydraulic coupling it replaced. The amount of volume change and spin can be varied by changing the vane positions. Therefore, depending on the location of the minimum air gap, electromagnetic forces can statically or dynamically load or unload the rotor bearings. ( This is rarely the fault of the VSD but is most often due to poor earthing or screening of the VSD and poor location of the control signal cables. ) the rectifier section converts the 60 Hz AC voltage and current into a direct current (DC) voltage and current. This is the reason why such VSD units' output frequencies and voltages satisfy the following equation: U1, U2 = output voltages at f1 and f2 Hz, V. Up-to-date VSDs utilize the “sensorless flux vector” principle [49,50], which is designed to control the AC motor's output torque. For example, a dental office must buy dental supplies, which usually cost about the same. Self-Changing Gears made semi-automatic transmissions for British Rail, and Voith manufacture turbo-transmissions for diesel multiple units which contain various combinations of fluid couplings and torque converters. n This leads to a change in transmission performance and so where unwanted performance/efficiency change has to be kept to a minimum, a motor oil or automatic transmission fluid, with a high viscosity index should be used. Correct operation of a fluid coupling depends on it being correctly filled with fluid. This comparison should help in making a more judicious choice of drive. If a coupling is deliberately designed to operate safely when under-filled, usually by providing an ample fluid reservoir which is not engaged with the impeller, then controlling its fill level may be used to control the torque which it can transmit, and in some cases to also control the speed of a load.[b]. [3], During 1930 The Daimler Company of Coventry, England began to introduce a transmission system using a fluid coupling and Wilson self-changing gearbox for buses and their flagship cars. [2,3,4] discusses sub-synchronous rotor instability in the overcritical electric generator and induction motor. About Phoenix Pumps Having our customers' backs — providing you with fluid handling solutions specifically engineered for efficiency and profitability — has always been our focus.We work with the world's top fluid technology manufacturers so our customers get innovative equipment that makes a real difference in performance and help reduce total cost of ownership. r [7] Generally speaking, multi-grade motor oils or automatic transmission fluids are used. Rev. The first diesel locomotives using fluid couplings were also produced in the 1930s[4]. Do you remember earlier in the chapter when we noted that when we measure the voltage and current in a pure sinewave ac circuit we are measuring the rms value? Stop-and-go driving will tend to operate the coupling in its least efficient range, causing an adverse effect on fuel economy. These devices used, instead, thyristors, extremely fast semiconductor switches like insulated gate bipolar transistors to create the output frequency. (These electronic bypasses are not independent; therefore, they use the same contactors and overloads, as does the VSD, so they are not totally independent.) Output direct current (DC) waveform from a “6-pulse” rectifier. In 1939 General Motors Corporation introduced Hydramatic drive, the first fully automatic automotive transmission system installed in a mass-produced automobile. Scoop control can be used for easily managed and stepless control of the transmission of very large torques. Hydrokinetic drives, such as this, should be distinguished from hydrostatic drives, such as hydraulic pump and motor combinations. As seen, the DC voltage has six pulses for a complete cycle; hence, the name of this rectifier type is “six-pulse.” There are rectifiers producing more pulses such as 12, 18, 24 and the higher the pulse number, the smoother the DC output. The PWM works by first converting the incoming ac power to dc using a diode bridge rectifier. These complications, along with the added costs involved, must be weighed against the potential benefit of bypass starters. method of throttle control through a vane or a damper causes a considerable waste of energy. This also generates additional high order harmonics. [8] However, hydraulic fluids, much like other fluids, are subject to changes in viscosity with temperature change. Finally, the calculation tool can also be applied to simulate measured vibration behavior in the field, to identify the cause and help to make a technical decision to assess and resolve vibration issues. Due to slippage that will occur in any fluid coupling under load, some power will always be lost in fluid friction and turbulence, and dissipated as heat. 5 The ratio of the sine wave's maximum voltage and the voltage of the generated pulses is called the “modulation,” which is about 50% in the first and almost 100% in the second case. This is to certify that variable speed fluid coupling of M/s Fluidomat Limited, Dewas (India) was installed on our ID Fan 250 KW @ 1490 RPM Motor in February 1995. The flexibility of a CVT with suitable control may allow the engine to operate at a constant RPM while the vehicle moves at varying speeds. Many types of variable speed drives have been used over the years, starting with dc drives used primarily in industrial applications, and mechanical drives that varied sheave diameter. [13] In the case of automotive applications, where loading can vary to considerable extremes, Variable speed fluid couplings Compact design coupled with reliability, our hydrodynamic coupling solution, is perfect for speed variation applications ranging from 100 kW up to 35 MW (up to 3,600 rpm). ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. In some countries this device is classified as ‘energy saving’ and attracts subsidies from the state. The coupling is working satisfactorily since then and we have been able to achieve an energy saving of 1330 units per day. Eng., in Fundamentals of HVAC Control Systems, 2008. Variable Cost A cost to a person or business that varies over time according to a number of factors. The converter is analyzed; design and considerations have been discussed. This enables accurate control of the motor speed over a broad range. Figure 2-25. The output voltage and current of a typical PWM unit are shown in Fig. Smoother DC waveforms have the advantage of minimizing the amount of harmonics, i.e., deviations from a pure sine wave. ( Gabor Takacs PhD, in Sucker-Rod Pumping Handbook, 2015. [2] The Hydramatic employed a fluid coupling. A continuously variable transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios.This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. VSD - DC/DC usage to drive compressors allows controlling and accurate measurements on speed and torque of compressor motors, and so enhancing its application characteristics. As seen, an 18-pulse rectifier basically eliminates all problems associated with harmonics and provides an efficient use of electrical power. These devices contain a controllable switch and the output AC frequency is adjusted by the speed of switching. Variable speed drives (VSDs) take the place of a starter. When using VSDs, the motor winding insulation will experience higher voltage stresses than when used with a direct AC connection due to the rapid voltage pulses and the transmission line effects in the connecting cables. Gabor Takacs Ph.D, in Electrical Submersible Pumps Manual (Second Edition), 2018. Figure 3 shows a schematic representation of a continuously variable hydraulic cam phasing system that uses engine oil as the hydraulic fluid. 5.20, the output voltage of these PWM-based VSDs takes the form of a series of voltage pulses, each of the same magnitude but having a different, controlled width. {\displaystyle n} One of the most important developments in recent years has been the advancement of variable frequency drive (VFD) technology. The output voltage of these VSDs takes the form of a series of voltage pulses, each of the same magnitude but having a different, controlled width. For example, the turbines can be aluminium castings or steel stampings and the housing can also be a casting or made from stamped or forged steel. The voltage is then filtered, smoothed and passed on to the PWM inverting section. They use inexpensive rectifiers with diodes and inverters with IBGTs (insulated gate bipolar transistors). In summary, VSDs using this new technology allow a much enhanced control of rod pumping operations. Fluid Flow Pressure Calculator Enter your application’s fluid properties, hose and coupling specifications, and our Fluid Flow Pressure Calculator will help identify your operational issues, so you can eliminate costly downtime, improve efficiency, and save money. is the impeller speed, and round the edges of a torus), there is no flow of fluid from one turbine to the other. As a fluid coupling operates kinetically, low-viscosity fluids are preferred. When a fluid coupling is used for braking it is also known as a retarder.[5]. Similar effects are also observed during the test measurements. Figure 5.20. Tip – Installing and commissioning of VSDs is an important factor in getting the best energy efficiency from the drive. Variable Inlet Vane with Constant Fan Speed. VSDs can be used for injection moulding machines to match the output of the hydraulic pump to the process needs. We use cookies to help provide and enhance our service and tailor content and ads. Figure 5.19. Inverter Variable Frequency Drive. This is a result of hot alignment conditions, which change the loading conditions on the bearings. The oil may be pumped back into the coupling when needed, or some designs use a gravity feed - the scoop's action is enough to lift fluid into this holding tank, powered by the coupling's rotation. These couplings are described as constructed under Vulcan-Sinclair and Daimler patents.[3]. During the development of the calculation tool, it was observed from theoretical predictions that linear forces, arising from rotor unbalances leading to significant vibration levels can throw the complete system into a strong non-linear state due to the non-linear behavior of oil film forces generated in the bearings. Fluids 6, 034201 (2021). It is low in the first cost, simple to operate and does not require more horsepower than other methods of control. On the other hand, the dental office must also pay the electric and gas and water bills, which may fluctuate considerably. The STC coupling contains a reservoir to which some, but not all, of the oil gravitates when the output shaft is stalled. [2] His patents from 1905 covered both fluid couplings and torque converters. Some other means of relieving the air pressure or reducing fan speed should be provided. r By continuing you agree to the use of cookies. The pressure from the fan and its horsepower requirement (within certain limitations) depend on this spin. They also provide a mechanical coupling between the drive and the load. They have both starting capability and overload protection built in. Conventional rotor dynamics analysis and stability analysis of rotor-bearing systems is performed based on linearized oil film stiffness and damping coefficients, which is sufficient to design most of the machine with accurate prediction of critical speed and overall vibration levels. Fluid couplings are used in many industrial application involving rotational power,[11][12] especially in machine drives that involve high-inertia starts or constant cyclic loading. Main components of a VSD unit. The most common VFDs used in HVAC applications are inverters using sine-coded pulse-width-modulation (PWM) technology. The choice between the two will be a matter of system requirements and an overall assessment of the ease of application, economy and accuracy of speed control in addition to the amount of energy it will be able to conserve. The first VSD units manufactured in the late 1970s used thyristors to create the AC waveform and produced a very crude approximation of a sine wave. Figure 18-152 shows the performance curve of a typical situation using the variable inlet vanes that control or limit the inlet volume and spin the air at the fan inlet. When using a bypass starter, it is important to consider how well the system will operate at full speed. 4.44. A VSD unit receives alternating voltage from the power supply at a constant (usually 60 Hz) frequency, internally rectifies this to a direct voltage, and then synthesizes an alternating voltage of any frequency at its output; output current fluctuates according to the load on the unit. R. Kree, L. Rückert, and A. Zippelius Phys. The fluid coupling originates from the work of Hermann Föttinger, who was the chief designer at the AG Vulcan Works in Stettin. is only an approximation. Voltage source inverters are commonly used in the ESP industry; they control the VSD's output voltage and the current fluctuates according to the load on the unit. Such variations can be in the flow of fluid and pressure of air or gas etc. Such power supplies come in two versions: voltage or current source inverters. Figure 4.34 shows two cases with an identical carrier frequency and thus with the same output frequency but with different maximum output voltages on the sine waveforms. 5 In electric motors used in variable frequency drives, various excitation forces exist due to the presence of mechanical and electromagnetic forces. This is based on the fact that both the magnetic flux density inside the motor and the torque developed by the motor change if the motor is supplied with variable frequency at a constant voltage. Six-step VSDs were bulky and unreliable and were almost completely replaced by the early 1990s with units using “pulsed-width modulation,” or PWM, in their inverters to create a more sinusoidal current. It is a constant and recurring drain on useful energy. 5.18): Figure 5.18. ) Meters are sold as “true rms” meters and are more costly than those which need the true sinewave input. The hydraulic system primarily consists of an off-axis gear-driven variable vane-type pump next to the valve body, and two control valve body assemblies. https://en.wikipedia.org/w/index.php?title=Fluid_coupling&oldid=993309250, Creative Commons Attribution-ShareAlike License, One connected to the input shaft; known as the, The other connected to the output shaft, known as the, If there is a difference between input and output angular velocities the motion has a component which is circular (i.e. Waveforms of a “six-step” VSD unit. ASME B16.5-2003 and ASME B16.5-1996 flange grades are available: Table 1A … Copyright © 2021 Elsevier B.V. or its licensors or contributors. ) is the impeller diameter. Conservation of energy is therefore the main criterion in the selection of static drives. Inductors, on the other hand, restrict the amount of current that charges the capacitors and thus increase the duration of current flow. Dr Gustav Bauer of the Vulcan-Werke collaborated with English engineer Harold Sinclair of Hydraulic Coupling Patents Limited to adapt the Föttinger coupling to vehicle transmission in an attempt to mitigate the lurching Sinclair had experienced while riding on London buses during the 1920s[2] Following Sinclair's discussions with the London General Omnibus Company begun in October 1926, and trials on an Associated Daimler bus chassis, Percy Martin of Daimler decided to apply the principle to the Daimler group's private cars. By 1933 the system was used in all new Daimler, Lanchester and BSA vehicles produced by the group from heavy commercial vehicles to small cars. Tip – Check with the VSD supplier for information on harmonic filtering. This paper will present the theory to calculate such effects. 4.43) creates a pulsating DC output presented in Fig. d The average total harmonic distortion (THD) for different pulse numbers changes as follows: Figure 4.44. With the advent of static technology, the trend is shifting in favour of static controls, particularly for drives that have to undergo frequent and wide speed variations during their normal course of operation, or which require very accurate speed control. To optimize the operating conditions of electrical motors, the use of AC power supplies with variable frequencies is a widely used method in many industries. Fluid couplings can also act as hydrodynamic brakes, dissipating rotational energy as heat through frictional forces (both viscous and fluid/container). Some manufacturers use silicon controlled rectifiers but the use of diodes provides better performance: much lower amount of harmonics and uniform, high power factor at all speeds. Tip – If electromagnetic compatibility is a concern then seek advice from the VSD manufacturer about how to improve earthing or screening and cable location. NEW ARTICLE Dynamics of a droplet driven by an internal active device. Manufacturers of industrial fluid couplings include Voith,[14] Transfluid,[15] TwinDisc,[16] Siemens,[17] Parag,[18] Fluidomat,[19] Reuland Electric[20] and TRI Transmission and Bearing Corp.[21]. A schematic of the PWM is shown in Figure 2-25. It also has widespread application in marine and industrial machine drives, where variable speed operation and controlled start-up without shock loading of the power transmission system is essential. The pressure plate, when applied, provides a mechanical direct drive coupling of the engine to the transmission. Select the flange material grade (group). the rectifier section converts the 60 Hz AC voltage into a DC voltage, the DC control section provides a smooth DC waveform to the next section, and. This means if you're accelerating in third gear, fourth gear can already be selected, so when it's time to shift, the computer simply releases one clutch and engages the other, for an almost seamless change. Fluid couplings larger than, say, 400 kW can be employed with ease in achieving the required speed control. A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power. Fig. Variable-speed drives are being increasingly used to operate high-speed compressors and pumps as a result of the high efficiency and reliability that they offer. Make sure this is done correctly. Variable speed drive (VSD) is a general term that refers to a pump driver that has a range of speeds—for example, from 2000RPM to 4000RPM. While the transmission is in gear, as engine speed increases, torque is transferred from the engine to the input shaft by the motion of the fluid, propelling the vehicle. An under-filled coupling will be unable to transmit the full torque, and the limited fluid volume is also likely to overheat, often with damage to the seals. {\displaystyle r(n^{2})(d^{5})} This popular control is simple and can be operated manually or automatically. 4.35 showing the characteristic chopped-up voltage waveform and the quite smooth current that very closely approximates a perfect sine wave. The function of this section (also called the DC bus) is to make the DC waveform as smooth as possible so that the next section (the inverter) receives a smooth DC voltage. Integrating of VSD - DC/DC systems in compressors have significant technical and economical advantages including significant energy savings, and consequently the related reductions in CO2 emissions, are possible through usages of these drives in a wide variety of applications in industry. The output frequency is controlled by adjusting the number of pulses per cycle (called the carrier frequency) and the output voltage is controlled by the width of the pulses. The stall speed is defined as the highest speed at which the pump can turn when the output turbine is locked and full input torque (at the stall speed) is applied. A fluid coupling cannot develop output torque when the input and output angular velocities are identical. Voltage output at different modulations. The output frequency is controlled by adjusting the number of pulses per cycle (called the “carrier frequency”) and the output voltage is controlled by the width of the pulses. Agrawal, in Industrial Power Engineering Handbook, 2001, Variable-speed drives are essential for many industrial applications requiring variable operating parameters during the course of operation. Capacitors store energy and smooth out the pulses in the DC waveform whenever the rectifier voltage drops. Robin Kent, in Energy Management in Plastics Processing (Third Edition), 2018. Variable speed drives (VSDs), also called adjustable speed drives (ASDs), are devices that can vary the speed of a normally fixed speed motor. The current in the motor very effectively approximates a sine wave because the motor is primarily an inductive device. d Increasing density of the fluid increases the amount of torque that can be transmitted at a given input speed. The originally used six-diode bridge configuration (see Fig. In addition, in order to omit the energy losses in DC compressors, a new zero current transition PWM forward converter is introduced, which applies a basic but vital auxiliary circuit. Output voltage is adjusted by changing the width and number of the voltage pulses while output frequency is varied by changing the length of the cycle. Where the torque needed to drive a load is proportionate to its speed. The torque transmitting capacity of any hydrodynamic coupling can be described by the expression From hydraulic system adjustment and maintenance to making factory-quality assemblies on the field, Gates manufactures hydraulic equipment and hose crimpers to improve your operational capacity and system service life with ease. By moving this scoop, either rotating it or extending it, it scoops up fluid from the coupling and returns it to a holding tank outside the coupling. In a seven-speed system, gears 1-3-5-7 will be on one rod, with 2-4-6 on the other. Waveforms of a VSD unit using pulsed-width modulation (PWM). A. Kayode Coker, in Ludwig's Applied Process Design for Chemical and Petrochemical Plants (Fourth Edition), 2015. The most prominent use of fluid couplings in aeronautical applications was in the DB 601, DB 603 and DB 605 engines where it was used as a barometrically controlled hydraulic clutch for the centrifugal compressor and the Wright turbo-compound reciprocating engine, in which three power recovery turbines extracted approximately 20 percent of the energy or about 500 horsepower (370 kW) from the engine's exhaust gases and then, using three fluid couplings and gearing, converted low-torque high-speed turbine rotation to low-speed, high-torque output to drive the propeller. 4.43): Figure 4.43. This eliminates the major limitation of the “volts per Hz” control mechanism that it does not control the torque of the motor. Variable speed drives are also used to control pumps on variable flow pumping systems and to control refrigeration compressors in centrifugal chillers. This is why a sine-wave filter is usually added to filter out harmonics and to prevent other electrical problems. Figure 2-27. This is a very complex use of a VSD and is dealt with more fully in Section 5.8. Generally speaking, the power transmitting capability of a given fluid coupling is strongly related to pump speed, a characteristic that generally works well with applications where the applied load does not fluctuate to a great degree. The variable frequency power supply uses solid state components to produce a pulse-width modulated current that varies the power and frequency supplied to the motor. For special high-speed machines, to evaluate the risk of machine instability with a greater degree of certainty, non-linear analysis has to be performed. One of the advantages of this control method is that NEMA B motors can be used, which, if compared to the universally used NEMA D motors (1) are about 10% more efficient, (2) are less expensive, and (3) have power factors close to unity. The inverter consists of high speed bipolar transistors that control both voltage and frequency sent to the motor. In HVAC systems, they are used primarily to control fans in variable air volume systems instead of other devices such as inlet vanes and discharge dampers. It contains switchable power electronic devices, normally bipolar Darlington transistors, but the latest units use insulated gate bipolar transistors (IGBTs) with very high switching speeds. The motion of the fluid is effectively toroidal - travelling in one direction on paths that can be visualised as being on the surface of a torus: An important characteristic of a fluid coupling is its stall speed. For hydroviscous fluid couplings, see. Outlet Damper with Constant Fan Speed. This advantage is not possible in a fluid coupling due to higher power losses. In most situations, being clear about rms does not matter as the waveform is close to a sinewave. Variable Speed Drive with Optional Starter, Gabor Takacs Ph.D, in Electrical Submersible Pumps Manual, 2009. Variable speed drives are more energy efficient than these other devices (their main advantage), but they also reduce noise generation at part-load, allow fans to operate at much lower loads without causing the fan to operate in surge (an unstable condition that can result in violent pulsations and possibly cause damage to the fan), and reduce wear on mechanical components such as belts and bearings. Motor current, as seen, is more sinusoidal than the square voltage wave because of the inductive characteristics of the AC motor. While a starter is not required when a VSD/VFD is used, one may be provided as a back up to the drive so that the motor can be run at full speed in case the drive fails. ( Fluid flywheels, as distinct from torque converters, are best known for their use in Daimler cars in conjunction with a Wilson pre-selector gearbox. Connecting the device between the power system and the pumping unit's prime mover, motor speed, and, consequently, pumping speed can be changed at will within a fairly broad range.