Rotational speed

Abstract: A circuit arrangement including a computer is built in an electrical jig saw where various data or information, such as the sort of the material of the workpiece, the thickness of the workpiece, desired degree of finish and way of cutting, are manually inputted via a keyboard so that the computer selects and determines optimum working condition, such as the sort of blade to be used, the locus of the blade, blade strokes per minute which is in proportion to the motor speed, and the necessity of application of coolant oil. The circuit arrangement also comprises circuitry for automatically controlling the rotational speed of the motor of the jig saw so that an actual speed of the blade equals a desired speed represented by strokes per minute. A display unit is coupled with the computer for indicating input and output data of the computer for supplying visual information to the user of the jig saw.

Abstract: The device comprises a rotationally driven surgical instrument incorporating a hand-held element having a mount rotatably installed therein for reception of interchangeable cutting and milling inserts, a driving motor for driving the mount receiving the tool inserts, a control unit for controlling the driving motor with means of setting the rotational speed and of preselecting the rotational speed range and direction of rotation as well as a digital indicator for displaying the rotational speed set up in each case. For the purpose of accessible storage of setting data, the control unit incorporates a non-volatile read-write memory for digital storage of rotational speeds, a code carrier as well as a coding/decoding arrangement.

Abstract: Mathematical models were developed to predict the transitions between the different forms of transverse motion of free-flowing bed materials in rotating cylinders: sliding, surging, slumping, rolling, cascading, cataracting and centrifuging. Model calculations of the limits between these types of bed motion compare well with measurements of experimental rotating cylinders as well as published results from industrial practice. The motion behavior can be represented on a Bed Behavior Diagram that plots wall friction coefficient and Froude number against the filling degree. From this study, scaling criteria for the bed behavior were found to be the Froude number, filling degree, wall friction coefficient, ratio of particle to cylinder diameter, angle of internal friction, and static and dynamic angles of repose. The transition criteria worked out and the Bed Behavior Diagram provides the user of rotary kilns the possibility to estimate the type of motion of the bed materials used from measured particle characteristics. As a result, the bed behavior can be influenced through selection of operating variables such as rotational speed and filling degree or installation of lifting bars and flights.

Abstract: The rotational speed of a pneumatic hand tool is adjusted in real time to maintain a selected speed level irrespective of exterior parameters affecting the performance of the tool. The apparatus is comprised of a rotational speed sensor installed directly on the tool, a digital microprocessor using control algorithms, and a valve to adjust the flow of air to the tool.

Abstract: The increasing penetration of variable speed wind turbines in the electricity grid will result in a reduction of the number of connected conventional power plants. This will lead to a reduction of inertia in the grid, as the rotational speed of a variable speed turbine and the grid are decoupled by a power electronic converter. A lower system inertia will result in larger and faster frequency deviations after occurrence of abrupt variations in generation and load. It is possible to implement an additional control loop in the power electronic converter of the turbine, which connects the turbine inertia directly to the grid. It is even possible, by control, to make a ‘virtual inertia’ that is larger than the real inertia. During a frequency drop additional power can be released to the grid with this control. This behaviour will be called inertial response. The additional power is obtained from the kinetic energy that is stored in the rotating mass of the turbine. In this contribution two different control strategies are investigated and compared with each other. A type of control that is equal to the primary frequency control of large power plants shows the best results, both with respect to the power that is needed to limit the frequency drop and with respect to electrical and mechanical stress of the turbine.