Starting Capabilities Research Articles

Design of a Low-Power Direct-on-Line Synchronous Reluctance Motor Based on the Modified Natural Flux Line Curve Approach

A direct-on-line synchronous reluctance motor (DOLSynRM) with a rotor topology defined by the natural flux line curve approach is studied as an alternative to an induction motor (IM) using a 1.5 kW, 50 Hz synchronous reluctance motor as an example. If an IM stator is used, a direct squirrel cage rotor replacement by a synchronous reluctance rotor equipped with a damper winding might not guarantee a sufficient starting performance. To ensure the strong enough starting capability, the natural flux line curve approach was modified in the motor design. The proposed approach was applied in the optimization of the DOLSynRM using a genetic algorithm. The optimization results show a clear tendency in the rotor design when trying to achieve a reliable starting capability and to maximize the steady-state performance of the DOLSynRM. Both the stator design and the rotor diameter of the optimized DOLSynRM are different from those of a corresponding squirrel cage IM. A DOLSynRM prototype was built and tested. It showed about a 5.4%-unit higher efficiency than the original prototype IM and acceptable starting performance under the rated load condition. The starting capabilities of the motors under study are considered with different loads. The locked rotor apparent power and current stay below permissible limits in both the IM and the DOLSynRM.

Learning curves, potential and speed in training of laparoscopic skills: a randomised comparative study in a box trainer

BackgroundThe effectiveness of practical surgical training is characterised by an inherent learning curve. Decisive are individual initial starting capabilities, learning speed, ideal learning plateaus, and resulting learning potentials. The quantification of learning curves requires reproducible tasks with varied levels of difficulty. The hypothesis of this study is that the use of three-dimensional (3D) vision is more advantageous than two-dimensional vision (2D) for the learning curve in laparoscopic training.MethodsForty laparoscopy novices were recruited and randomised to a 2D Group and a 3D Group. A laparoscopy box trainer with two standardised tasks was used for training of surgical tasks. Task 1 was a positioning task, while Task 2 called for laparoscopic knotting as a more complex process. Each task was repeated at least ten times. Performance time and the number of predefined errors were recorded. 2D performance after 3D training was assessed in an additional final 2D cycle undertaken by the 3D Group.ResultsThe calculated learning plateaus of both performance times and errors were lower for 3D. Independent of the vision mode the learning curves were smoother (exponential decay) and efficiency was learned faster than precision. The learning potentials varied widely depending on the corresponding initial values and learning plateaus. The final 2D performance time of the 3D-trained group was not significantly better than that of the 2D Group. The final 2D error numbers were similar for all groups.ConclusionsStereoscopic vision can speed up laparoscopic training. The 3D learning curves resulted in better precision and efficiency. The 3D-trained group did not show inferior performance in the final 2D cycle. Consequently, we encourage the training of surgical competences like suturing and knotting under 3D vision, even if it is not available in clinical routine.

Comparative Parameters Investigation of Composite Solid Rotor Applied to Line-Start Permanent-Magnet Synchronous Motors

This paper presents a composite solid rotor applied to improve the starting and synchronization capabilities of the line-start permanent magnet synchronous motor (LSPMSM). The rotor is mainly composed of solid steels to employ their high starting torque. A squirrel cage and some air slots are designed to be added on the rotor surface. During the starting process, the cage carrying eddy currents constitutes a branch in parallel with that of the solid steel, and hence decreases the total rotor impedance. Meanwhile, the surface slots enlarge the eddy current area of the solid steel and further reduce the rotor resistance. All these rotor parameters turning smaller lead to a higher induction torque, and thus enhance the motor performances of starting and synchronization. A set of comparisons about rotor parameters, induction torques, and speed-time responses are implemented among the LSPMSMs with the composite solid rotor and other solid ones lacking cage or slots. Results of the comparisons validate the advantages of the cage slot attachment as well as the motor performance improvement by applying the composite solid rotor.

Vibration and Noise Analysis of 4Ф Switched Reluctance Motor Drive

The Switched Reluctance Motor (SRM) is getting large attention for industry application due to their simple construction, high starting capabilities, high reliability, and high efficiency and also rotor carries no windings, no slip-rings there is no brushes, it requires less maintenance. In spite of the merits, it had some demerits like acoustic noise and vibration is one of major issues in SRM. The DSP-TMS320F28335 processor were implemented due to their high performance for the control applications.In this work the Random Pulse Width Modulation (RPWM) technique is used to reduce the acoustic noise and vibration by varying random turn on and turn off angle control.The acoustic noise and vibration signals are measured using accelerometer and sound level meter in 1HP, 8/6poles of SRM drive. The experimental analysis of vibration signals are measured using Lab VIEW at different speeds and load conditions. The acoustic noise signals are measured using Sound level meter .Both the Acoustic and vibrations are analyzed experimentally for different speeds and load conditions. The experimental results show that the noise and vibration analysis and also compare the sinusoidal PWM is better than Random PWM techniques. DOI: http://dx.doi.org/10.11591/telkomnika.v14i3.7965

Hydrogen Peroxide-Based Gas Generator Design and Performance Testing as an Aircraft Emergency Power Unit

Hydrazine monopropellant is often used with a spontaneous catalyst a high-performance aircraft emergency power unit (EPU) and in aerospace propulsion; however, it is toxic and requires special handling. A hydrogen peroxide (H2O2)-based gas generator, which is suitable for a new family of environmentally friendly monopropellants and is a substitute for toxic hydrazine in EPUs, is introduced in this study. A MnO2/Al2O3 catalyst for H2O2 decomposition, superior to silver catalysts at normal starting and reactivity capabilities, was selected and developed. The performance tests of coupling the gas generator with a turbocharger showed acceptable results for an aircraft EPU with decomposition above 90%, 37 kW maximum turbine output power, and a maximum starting delay of 1.2 s during normal starting operation. The gas generator also demonstrated satisfactory performance during repeated pulse operation at a pulse duration of 3 s and 60 s under various output conditions.

Dynamic Modeling of Starting Capabilities of Liquid Propellant Rocket Engines

An analytical technique is developed for predicting the mass flow rate and heat addition in a liquid propellant rocket engine fuel system during the initial portion of an engine start. The analysis emphasizes nozzle jacket heat exchange; specifically, flow and heat transfer characteristic influence on power availability. The outstanding feature of this model is the accurate representation of fluid properties during phase change, and the subsequent affect on mass flow rates. The model also considers conduction and energy storage within the nozzle walls and makes use of extensive hydrogen heat convection data. The analytical technique is applied to a proposed 20,000-Ib thrust expander engine for the determination of the minimum initial nozzle jacket metal temperature that will promote starting at various operating conditions. The energy content of engine fuel flow during the initial portion of startup is compared to predicted turbomachinery torque requirements to determine start capability. Starting capability is determined for various initial nozzle metal temperatures at fuel inlet pressures of 50 and 70 psi at sea level. The minimum initial jacket metal temperature that will produce enough energy to overcome predicted turbine breakaway torque is determined to be 135°R for 70-psi and 385°R for 50-psi inlet pressures.