Analysis of Preload of Three-Stator Ultrasonic Motor

The pre-pressure device of the ultrasonic motor plays a vital role in the design of the entire motor structure, the contact state of the stator and rotor of the motor, dynamic properties of the stator, friction and wear characteristics of the rotor; even the mechanical behaviors of the entire electric machinery have a profound impact. Appropriate pre-pressure is conducive to the smooth operation of the ultrasonic motor, so that the output performance remains excellent, reducing wear and effectively extend the service life of the motor. Therefore, the research on pre-stress is of great significance, as it can better optimize the structure of the three-stator ultrasonic motor and lay the foundation for the stable operation of the motor. First, this paper introduces the construction of the motor as a whole and the pre-pressure device briefly described the working mechanism of the motor, and then introduces the influence of the pre-pressure on the stator and rotor contact models, the position of the constant velocity point, and the modal frequency. Finally, the motor output under different pre-pressures is discussed. The performance experiment has determined the optimal pre-pressure interval, which provides help for its subsequent optimization.

Online Frequency Response Analysis of Electric Machinery through an Active Coupling System Based on Power Electronics

This paper presents an innovative concept for the online application of Frequency Response Analysis (FRA). FRA is a well known technique that is applied to detect damage in electric machinery. As an offline technique, the machine under testing has to be removed from service—which may cause loss of production. Experimental adaptations of FRA to online operation are usually based on the use of passive high pass coupling—which, ideally, should provide attenuation to the grid voltage, and at the same time, allow the high frequency FRA signals to be injected at the machine. In practice, however, the passive coupling results in a trade-off between the required attenuation and the useful area obtained at the FRA spectra. This paper proposes the use of an active coupling system, based on power electronics, in order to cancel the grid voltage at the terminals of FRA equipment and allow its safe connection to an energized machine. The paper presents the basic concepts of FRA and the issue of online measurements. It also presents basic concepts about power electronics converters and the operating principles of the Modular Multilevel Converter, which enables the generation of an output voltage with low THD, which is important for tracking the grid voltage with minimum error.

Financial and Growth Analysis: A Comparative Study of Economic Sectors of Pakistan

performance across the sectors. Taking economic group of an economy the unit of analysis, this research presents a comparative financial ratios analysis of economic groups composed of listed companies at Pakistan Stock Exchange (PSE). The analysis is based on the profitability, liquidity, efficiency, leverage, growth and trends over a period of time using 5 years data of non-financial listed companies. The results show that profitability ratios for Food, Chemicals, Cement, Motor vehicle, Fuel & energy sector and Coke sectors are performing above the overall average R.O.A and NPM while the Textile, Sugar, Manufacturing, Minerals, Information and Communication, Electric machinery and Other Services economic groups are performing below the overall averages. Sales growth of Manufacturing, Mineral product, Cement and Other services activities economic groups are performing above 50%. While Textile, Sugar, Food, Chemicals products, Motor vehicle, Fuel & energy, Info. & transport services, Coke and refined pet., Paper products and Electric machinery economic groups are performing below 50%. Sugar economic group has liquidity and total asset turnover ratio above overall average but the profitability of this economic group is below overall average. It means that the economic group is not properly utilizing its liquidity for generation of profits. Similarly, Textile sector has profitability, efficiency and liquidity below the overall average of economic groups.

Motor Intelligence Versus Vibration Analysis for Early-Stage Diagnosis of Electric Submersible Pumps

The main objective of this paper is to investigate the condition monitoring based on electric signature analysis for electric submersible pumps (ESPs) as introduced in our previous paper, SPE-201169-MS. While an ESP core physical concept is similar to other rotary electric machinery, they have unique features which make their selection, installation and operation different than typical rotating equipment applications. For the purpose of this study, a scale-down ESP system and flow loop was utilized to replicate an actual ESP application. Condition monitoring of the ESP was completed with mechanically and electrically induced vibrations and compare the results vis-à-vis those obtained by a common vibration analysis method. Furthermore, by running the ESP at various operation points, we show how the mechanical and electrical efficiency of the pump, induction motor and variable frequency drive are intertwined. This observation may suggest an interesting insight for further discussion on ESP optimization.

Generative Optimization for Automatic Creation of 3D CAD Platforms

The efficient creation of 3D CAD platforms can be achieved by the optimization of their design process. The research presented in this article showcases a method for allowing such efficiency improvement. The method is based on the DMADV six sigma approach. During the Define step, the definition of the scope and design space is established. In the Measure step, the initial evaluation of the platforms to be improved is done with the help of a Metrics framework for 3D CAD platforms. The Analyze Step includes the identification and optimization of the systems’ model of the process based on the architecture and the multiple objectives required for the improvement. The optimization method used that is based on evolutionary algorithms allows for the identification of the best improvement alternatives for the next step. During Design step of the method, the improvement alternatives are planned and executed. In the final Verification step, the evaluation of the improved process is tested against the previous status with the help of the Metrics Framework for 3D CAD platforms. The method is explained with an example case of a 3D CAD platform for creating metallic boxes for electric machinery.

On the Estimation of Cross-Firm Productivity Spillovers with an Application to FDI

We develop a novel methodology for the proxy variable identification of firm productivity in the presence of productivity-modifying learning and spillovers which facilitates a unified "internally consistent" analysis of the spillover effects between firms. Contrary to the popular two-step empirical approach, ours does not postulate contradictory assumptions about firmproductivity across the estimation steps. Instead, we explicitly accommodate crosssectional dependence in productivity induced by spillovers which facilitates identification of both the productivity and spillover effects therein simultaneously. We apply our model to study cross-firm spillovers in China's electric machinery manufacturing, with a particular focus on productivity effects of inbound FDI.

Aspects regarding the specific tests applicable to electric motors with type of protection increased safety „e”

Evaluation of explosion-proof protected electrical equipment in scope of certification is extremely important considering the risk of explosion that has to be minimized in order to ensure life safety and health of workers and to prevent damaging of property and the environment, as well as free movement of goods when they meet the essential safety requirements at European level. Most of the equipment operating in potentially explosive atmospheres is represented by electric motors, which in most situations act on various other elements (e.g. pumps, valves, fans etc.). Even if electric motors for explosive atmospheres are designed and manufactured following some of the same principles as the ones used for other electric machinery, they have certain particularities related to their field of use. Thus, a series of specific restrictions and tests are required to be considered in their case. The purpose of this paper is to present the importance of the specific tests for electric motors with type of protection increased safety „e” designed to be used in explosive atmosphere.