Mechanical adjustable speed

The two AC drive systems used on extruders are the adjustable transmission ratio drive and the adjustable frequency drive. The adjustable transmission ratio drive can be either a mechanical adjustable speed drive or an electric friction clutch drive. 

There are four basic types of mechanical adjustable speed (MAS) drives belt, chain, wooden block, and traction type. The latter two are not used on extruders because they are limited to low input speeds and easily damaged by shock loads [1, 2],... 

Mechanical adjustable speed drives, nowadays, are rarely used in extruders because they are maintenance intensive, have limited speed control and speed ratio, and their power efficiency is not very good. 

Flocculation units should have multiple compartments and should be equipped with adjustable speed mechanical stirring devices to permit meeting changed conditions. In spite of simplicity and low maintenance, non-mechanical, baffled basins are undesirable because of inflexibility, high head losses, and large space requirements. Mechanical flocculators may consist of rotary, horizontal-shaft reel units as shown in Figure 9. 

Motor Torque, 651 Power Factor for Alternating Current, 652 Motor Selection, 653 Speed Changes, 654 Adjustable Speed Drives, 659, Mechanical Drive Steam Tmbines, 659 Standard Size Turbines, 661 Applications, 662 Mtyor Variables Affecting Turbine Selection and Operation,... 

Figure 14.1 illustrates a simple dead-stop end-point assembly or a Karl Fischer titration apparatus. The titration vessel is fitted with a pair of identical platinum electrodes, a mechanical stirrer with adjustable speed, and a burette. It will be observed that absolutely little or no current may flow unless and until the solution is totally free from any polarizing substances this could perhaps be due to the absorbed layers of oxygen and hydrogen on the anode and cathode respectively. However, the current shall flow only when the two electrodes... 

Throttling of the suction of centrifugal and axial compressors wastes less power than throttling the discharge. Even less power is wasted by adjustment of built-in inlet guide vanes with a servomechanism which is a feedback control system in which the controlled variable is mechanical position. Speed control is a particularly effective control mode, applicable to large units that can utilize turbine or internal combustion drives control is by throttling of the supply of motive fluids, steam or fuel. 

When Fourier transform infrared (FTIR) spectrometers first appeared on the market in the early 1970s, they were bulky and expensive (more than 100,000) and required frequent mechanical adjustments. For these reasons, their use was limited to special applications in which their unique characteristics (great speed, high resolution, high sensitivity, and excellent wavelength precision and accuracy) were essential. Currently, however, FTIR spectrometers have been reduced to benchtop size and have become very reliable and easy to maintain. Furthermore, the simple models are now priced similarly to simple dispersive spectrometers. Hence, FTIR spectrometers are largely displacing dispersive instruments in most laboratories. 

A small fraction of the energy flow into a component of the wave spectrum flows into wave components with small wave numbers respectively frequencies due to weak nonlinear interaction between wave components of different wave numbers. These energy flow forms the low-frequency part of the spectrum and generates the kernels of the wave spectrum that are able to grow when the wind speed increases. This mechanism adjusts the wave spectrum to varying wind velocities. 

Until recently, most unwinders were supplied with an AC motor, direct coupled, or with an air clutch, running at a fixed payoff speed, or possibly with a mechanical variable-speed mechanism that was manually adjusted. Loop control consisted of a switching device (either mechanical or photoelectric) to turn the... 

The basic principles of the tape casting process are included in most of these machines whether they are laboratory casters or production-scale models. The major components needed for tape casting include a solid, level casting surface, a drying chamber with a built-in means for controlling the airflow over the drying tape, an adjustable speed carrier drive control with a constant speed regulation mechanism, an air heater to control the temperature of the filtered feed air to the... 

In a flask equipped with an explosion-proof mechanical stirrer with adjustable speed, an additional funnel, a thermometer, and a reflux condenser, 80 gm of anhydrous sodium sulfate is dissolved in 400 gm of water. Then 8 gm of a lO o aqueous solution of sodium poly(acrylate) is added as the suspending agent. After the addition of 100 gm (1.16 moles) of inhibited methacrylic acid containing 0.2 gm (0.0008 mole) of benzoyl peroxide, the reaction system is stirred continuously but not too rapidly and heated at 80 C with a water bath for approximately 2.5 hr. A small quantity of the 1097o aqueous solution of sodium poly(acrylate) is maintained in the addition funnel throughout the process so that part of this reagent may be added if there are indications of lump formation. 

Unvulcanized Latex and Latex Compounds. A prime consideration has to be the fluid-state stabihty of the raw latex concentrate and hquid compound made from it. For many years, the mechanical stabihty of latex has been the fundamental test of this aspect. In testing, the raw latex mbber content is adjusted to 55% and an 80 g sample placed in the test vessel. The sample is then mechanically stirred at ultrahigh speed (ca 14,000 rpm) by a rotating disk, causing shear and particle cohision. The time taken to cause creation of mbber particle agglomerates is measured, and expressed as the mechanical stabihty time (MST). 

This is why an induction motor ceases to run at synchronous speed. The rotor, however, adjusts its speed, N such that the induced e.m.f. in the rotor conductors is Just enough to produce a torque that can counter-balance the mechanical load and the rotor losses, including frictional losses. The difference in the two speeds is known as slip. S, in r.p.m. and is expressed in terms of percentage of synchronous speed, i.e. 

This senses the speed of the machine and performs extremely fast and accurate adjustments in the fuel supply to the PM. In turn it regulates the speed and the output of the PM within predefined limits, depending upon the droop of the PM. The governor may be a mechanical (manual), hydraulic or electronic (automatic) device. 

Gas turbine power adjustments in a utility application require that the mechanical speed must remain constant due to unacceptable consequences of frequency fluctuations. The control is obtained by IGV adjustments to reduce the flow at off-design loads and to maintain the high exhaust gas temperature. 

Control systems for process compressors become an absolute necese whenever deviations from a single operating point occur in the process system. These systems consist of a mechanism that can sense performance and, by making a calculation, adjust the process controls with satisfactory speed, accuracy, and stability. 

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