Low-inertia Motor Research Articles

A New Pulsatile Volumetric Device With Biomorphic Valves for the In Vitro Study of the Cardiovascular System

A pulsatile mock loop system was designed and tested. This prototype represents a versatile, adjustable, and controllable experimental apparatus for in vitro studies of devices meant to interface with the human circulatory system. The pumping system consisted of a ventricular chamber featuring two biomorphic silicone valves as the inlet and outlet valves. The chamber volume is forced by a piston pump moved by a computer-controlled, low-inertia motor. Fluid dynamic tests with the device were performed to simulate physiological conditions in terms of cardiac output (mean flow of 5 and 6 L/min, with beat rates from 60 to 80 bpm), of rheological properties of the processed fluid, and of systemic circulation impedance. The pulsating actuator performed a good replication of the physiological ventricular behavior and was able to guarantee easy control of the waveform parameters. Experimental pressure and flow tracings reliably simulated the physiological profiles, and no hemolytic subatmospheric pressures were revealed. The performance of the prototype valves was also studied in terms of dynamic and static backflow, effective orifice area, and pressure loss, resulting in their applicability for this device. Mechanical reliability was also tested over 8 h. The device proved to be a reliable lab apparatus for in vitro tests; the pumping system also represents a first step toward a possible future application of pulsating perfusion in the clinic arena, such as in short-term cardiac assist and pulsatile cardiopulmonary bypass.

A Hybrid Drive Merging a Servo-Controlled Motor and a Spring Mechanism

Spring mechanisms have demonstrated their high reliable performance by operating thousands of circuit breakers (CBs) safely all over the world for decades under the most severe conditions. This well-known technology could be improved, when merged with a servo motor system. The result is a hybrid drive, which offers the accuracy and flexibility of servomechanisms and the reliability of spring operating mechanisms. The paper starts with a reminder of the state of the art of operating mechanisms, followed by an overview of spring mechanisms with the aim of identifying potential improvements. The remaining part is dedicated to the first evolution of the hybrid drive. The architectural description emphasizes the reliability aspects, especially due to the application of redundant tripping circuits, allowing the tripping operation without either an auxiliary power supply or electronic support. Test results are discussed. The conclusion illustrates that if technical benefits are obtained, the cost of some critical components still remains high. The applications of such a hybrid technology are restricted today to specific applications. As the prices of electronic systems decrease with time and, hopefully, the cost of low inertia motors, the architecture of operating mechanisms could be dramatically modified and tightly merged with the CB. The advantages of hybrid drives could be decisive for the long-term future.

Bus transfer of multiple induction motor loads in a 400 megawatt fossil power plant

A computer model capable of simulating multiple induction motors during bus transfer is described and its results compared with field tests. Optimum switching times are specified based on bus residual voltage and phase angle that will maintain motor inrush currents below ANSI/NEMA criteria. Recent papers have documented the inadequacy of the ANSI/NEMA resultant V/Hz criteria for assuring that motor-shaft torques remain below acceptable levels following bus transfer. The presented results support these findings, but indicate that the combination of high and low-inertia motors fed from the same bus will reduce motor peak-shaft torques when compared to individual transfer of low-inertia motor/pump units alone. >

Coulometric titration of carbon dioxide on the micro scale

A method is described for the coulometric titration of milligram and submilligram amounts of carbon dioxide. Carbon dioxide is absorbed and titrated in dry acetone containing about 0.5% of methanol and saturated with potassium iodide, in a two-compartment cell. Thymol Blue is used as visual indicator. Current integration is carried out by means of a low inertia motor or a solid-state integrator. The generation efficiency is 99-100%. The method has been applied to the determination of small amounts of carbon (0-1 mg) in organic and inorganic materials and in aqueous solution.

An autonomous optical method of determining the orientation of an Earth satellite in space: G.N. Krylovet al.: (pp. 145–153)

A rapid combustion technique in an oxygen atmosphere followed by a quantitative electrolysis of the initial quantity of water vapor produced is used for the microdetermination of carbon and hydrogen in organic compounds. The carbon dioxide also produced by combustion may be determined either by converting it to water vapor with subsequent electrolysis, or if need be, by quantitative gas chromatography. Both the carbon dioxide and water signals are integrated by inexpensive, low-inertia motors and the absolute amounts of carbon and hydrogen are obtained from respective calibration curves. The time required for a complete microanalysis is usually ten minutes or less, including the weighing of a 1 mg. sample. The absolute error of the method is approximately 0.5% for carbon and 0.1% for hydrogen for samples ranging from 0.5 to 1.5 mg.

A rapid instrumental method for the microdetermination of carbon and hydrogen in organic compounds

A rapid combustion technique in an oxygen atmosphere followed by a quantitative electrolysis of the initial quantity of water vapor produced is used for the microdetermination of carbon and hydrogen in organic compounds. The carbon dioxide also produced by combustion may be determined either by converting it to water vapor with subsequent electrolysis, or if need be, by quantitative gas chromatography. Both the carbon dioxide and water signals are integrated by inexpensive, low-inertia motors and the absolute amounts of carbon and hydrogen are obtained from respective calibration curves. The time required for a complete microanalysis is usually ten minutes or less, including the weighing of a 1 mg. sample. The absolute error of the method is approximately 0.5% for carbon and 0.1% for hydrogen for samples ranging from 0.5 to 1.5 mg.

A Fourier Analyser for Optical Frequency Response Determinations

The frequency response of an optical system may be derived from photoelectric image scanning data by a comparatively simple technique. The scanning movement is used to drive a sine-cosine potentiometer, fed by the photoelectric scanning signal, and integration of the product so formed is carried out with a low-inertia motor. Sine and cosine terms are available, and the successive Fourier coefficients are obtained by an alteration of potentiometer gearing. Values obtained with the apparatus are compared with those resulting from an equivalent digital electronic computation.