Browsing Faculty of Engineering and Technology by Author "Yanev, K.M."
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Yanev, K.M. (University of Botswana, www.ub.bw, NaN, 2007)[more][less]
Abstract: By the turn of the century, Botswana will be 34 years old as an independent nation. Reflecting on the past, is a background of tremendous achievements from a socio-economic development perspective. The achievements could not have been possible if it was not for the contribution of the construction industry. The construction industry’s (CI) contribution to socio-economic development may be viewed from many areas, among them, creating employment, wealth and demand for manufactured goods, infrastructure and producing factors of production (e.g. office space, factory shells, roads, etc) for other sectors. However, the relationship between the general economy and the CI has not been established explicitly despite numerous studies. Using Botswana’s CI and the economy, some of the paradigms proposed in previous studies revisited. URI: http://hdl.handle.net/10311/1063 Files in this item: 1
Yanev_BJT_2007.pdf (928.5Kb) -
Yanev, K.M.; Obok Opok, A.; Litchev, A. (University of Botswana, www.ub.bw, NaN, 2004)[more][less]
Abstract: Maintenance of the proper power factor is a very important matter for the industry and for the economy of any country. A study of the power factor value for a number of industrial plants in Botswana shows that they operate at power factors lower that the optimal values. If a plant power factor is different from its optimal value, this will cause considerable loses in terms of investments for large power generation and supply equipment and in terms of heat dissipation from the supply lines and other equipment. To improve the power factor and keep it at an optimal value, there are a number of preventative measures, as well as corrective actions that could be implemented. The power factor of a plant changes, depending on the number of electrical units operating at a time. After a full analysis of the power factor issue and its optimal case, are automatic control is designed that may maintain the power factor of a plant within values close to optimal. Similar automatic power factor control system can be introduced for all industrial plants with unsatisfactory power factor throughout the country that can improve considerably the efficiency of power utilization. URI: http://hdl.handle.net/10311/1062 Files in this item: 1
Yanev_BJT_2004.pdf (1.049Mb) -
Litchev, A.I.; Yanev, K.M. (University of Botswana, NaN, 2006)[more][less]
Abstract: Analysis of the induction motor failures show, that a significant number of motors are damaged due to single phasing.At such conditions the current increases rapidly and the motor is subjected to burnouts and consequently to long downfalls in the corresponding industry.Normally all motors are protected against thermal overloading by bimetal relays, but they are not always capable to ensure protection at single phasing.A secure protection is needed to trip the motor off in any case of single phasing especially for high power motors. The problems related to the motor protection against single phasing are discussed in this paper paper and for ensuring of such protection an electronic circuit is proposed and described. The circuit reacts immediately whenever a motor line current gets zero.A signal from this circuit switches off the motor starter on failures of anyone of the three phases. In such way the motor burnouts and downfalls are prevented. URI: http://hdl.handle.net/10311/622 Files in this item: 1
Litchev_BJT_2006.pdf (1.753Mb) -
Litchev, A.I.; Yanev, K.M. (University of Botswana, NaN, 1999)[more][less]
Abstract: Electromagnets are essentials for the operation of relays, contactors and other electromagnetic apparatus and take part in driving control and protective circuits of industrial processes and power systems. Performance of each electromagnet affects the driving time and the stability of operation of such circuits. This paper examines the improvement of the performance of AC electromagnets by using two diodes. The theoritical analysis lead to expressions for calculating the maximum, average and minimum values of coil-currents. Due to the electromagnetic processes in the coil, the current becomes pulsating but unidirectional and better force-gap characteristics are achieved. Consideration are made for reduction of the mass ferromagnetic and copper materials in the electromagnets and for decreasing teh responding time. URI: http://hdl.handle.net/10311/683 Files in this item: 1
Litchev_BJT_1999.pdf (924.8Kb)
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