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Papers by Kremena Dimitrova

AIP Conference Proceedings, Dec 31, 2022

Inženerni nauki, Jun 3, 2024

The authors propose a multidisciplinary approach and algorithm for the study and evaluation of th... more The authors propose a multidisciplinary approach and algorithm for the study and evaluation of the reliability and performance quality of anti-hail missiles and their control system. When examining the objects and systems in question, it is necessary to have a priori information about the risk of a particular (catastrophic, emergency) situation causing danger, damage, loss of human lives and resources, etc. In the absence of such information, accelerated tests of the systems are carried out to ensure that they are adequate in terms of quality, reliability and operational risk (guaranteed by the manufacturer). The algorithm is implemented in a similar missile control system.

In this paper we shall examine the reliability of technological innovation systems as part of hum... more In this paper we shall examine the reliability of technological innovation systems as part of human evolution. Briefly explained are the basic definitions of these systems and the prehistory of their dialectics. The aim is to analyze and evaluate the development of certain technological industries in terms of the reliability of information about the structures and processes taking place in them.

This report presents a new structural design of the control channel for the mainstream traction m... more This report presents a new structural design of the control channel for the mainstream traction modulus. The linear part of which determines both the dynamics of the system and the component of the stator current. It is shown the transfer function of the structural scheme as a whole and there are introduced cross-links. It is also shown a structural scheme for direct compensation of the cross-links. It is proposed a structural diagram of the electric drive system while taking into account the angular error of the support coordinate system.

The Journal of CIEES, Jun 3, 2021

During the operation of electric induction motors used to drive passenger elevators, electro-mech... more During the operation of electric induction motors used to drive passenger elevators, electro-mechanical transient processes occur, which can cause unacceptable dynamic loads and vibrations. In this regard, research is needed both at the design stage and for operating elevator systems to determine the arising impact currents and torques, in order to propose solutions for their limitation within pre-set limits. Paper deals with starting processes in a two-speed induction motor drive of a passenger elevator. The equations for the voltages of the induction motor are presented in relative units in a coordinate system rotating at a synchronous speed. The values have been obtained for the torques, the rotational frequencies and the currents when starting at a high speed and passing from high to low speed.

2023 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST)

E3S Web of Conferences

When studying electric drives, it is necessary to jointly analyze the processes in the electric p... more When studying electric drives, it is necessary to jointly analyze the processes in the electric power and control circuits of the electric motor as the main component determining the overall performance and in the mechanical executive part. The paper deals with the variation of the occurring torques, the currents flowing in the individual phases and the electrical power losses in the operation of a medium voltage electric drive of a pump unit from the point of view of energy efficiency. Emphasis is placed on the joint operation of the pump as a mechanism and the driving electric motor, studying the complete electromechanical system. During the studies, significant attention has been paid to the mathematical description and modeling with subsequent computer simulation of the ongoing electromagnetic and electromechanical processes. Different ways of controlling the motor have been applied - by softstarter and by frequency control. Also values for the duration of the start-up process h...

2020 21st International Symposium on Electrical Apparatus & Technologies (SIELA), 2020

The wide range of differences in conditions (temperature, pressure, humidity, vibrations, radiati... more The wide range of differences in conditions (temperature, pressure, humidity, vibrations, radiation) for communication equipment leads to hard demands towards the tolerances of the input parameters of the compound electronics circuits. The mentioned demands in case of electronic circuits are maintained with reducing of the tolerances of the functional elements mainly and using of new technical solution, which to give minimum influence of the destabilizing factors. The second method is much more perspective. In such a case this way gives an manual for establishing of an optimum technical decision for designing of communication equipment and an example how to use it.

This report presents a new structural design of the control channel for the mainstream traction m... more This report presents a new structural design of the control channel for the mainstream traction modulus. The linear part of which determines both the dynamics of the system and the component of the stator current. It is shown the transfer function of the structural scheme as a whole and there are introduced cross-links. It is also shown a structural scheme for direct compensation of the cross-links. It is proposed a structural diagram of the electric drive system while taking into account the angular error of the support coordinate system.

AIP Conference Proceedings, Dec 31, 2022

Inženerni nauki, Jun 3, 2024

The authors propose a multidisciplinary approach and algorithm for the study and evaluation of th... more The authors propose a multidisciplinary approach and algorithm for the study and evaluation of the reliability and performance quality of anti-hail missiles and their control system. When examining the objects and systems in question, it is necessary to have a priori information about the risk of a particular (catastrophic, emergency) situation causing danger, damage, loss of human lives and resources, etc. In the absence of such information, accelerated tests of the systems are carried out to ensure that they are adequate in terms of quality, reliability and operational risk (guaranteed by the manufacturer). The algorithm is implemented in a similar missile control system.

In this paper we shall examine the reliability of technological innovation systems as part of hum... more In this paper we shall examine the reliability of technological innovation systems as part of human evolution. Briefly explained are the basic definitions of these systems and the prehistory of their dialectics. The aim is to analyze and evaluate the development of certain technological industries in terms of the reliability of information about the structures and processes taking place in them.

This report presents a new structural design of the control channel for the mainstream traction m... more This report presents a new structural design of the control channel for the mainstream traction modulus. The linear part of which determines both the dynamics of the system and the component of the stator current. It is shown the transfer function of the structural scheme as a whole and there are introduced cross-links. It is also shown a structural scheme for direct compensation of the cross-links. It is proposed a structural diagram of the electric drive system while taking into account the angular error of the support coordinate system.

The Journal of CIEES, Jun 3, 2021

During the operation of electric induction motors used to drive passenger elevators, electro-mech... more During the operation of electric induction motors used to drive passenger elevators, electro-mechanical transient processes occur, which can cause unacceptable dynamic loads and vibrations. In this regard, research is needed both at the design stage and for operating elevator systems to determine the arising impact currents and torques, in order to propose solutions for their limitation within pre-set limits. Paper deals with starting processes in a two-speed induction motor drive of a passenger elevator. The equations for the voltages of the induction motor are presented in relative units in a coordinate system rotating at a synchronous speed. The values have been obtained for the torques, the rotational frequencies and the currents when starting at a high speed and passing from high to low speed.

2023 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST)

E3S Web of Conferences

When studying electric drives, it is necessary to jointly analyze the processes in the electric p... more When studying electric drives, it is necessary to jointly analyze the processes in the electric power and control circuits of the electric motor as the main component determining the overall performance and in the mechanical executive part. The paper deals with the variation of the occurring torques, the currents flowing in the individual phases and the electrical power losses in the operation of a medium voltage electric drive of a pump unit from the point of view of energy efficiency. Emphasis is placed on the joint operation of the pump as a mechanism and the driving electric motor, studying the complete electromechanical system. During the studies, significant attention has been paid to the mathematical description and modeling with subsequent computer simulation of the ongoing electromagnetic and electromechanical processes. Different ways of controlling the motor have been applied - by softstarter and by frequency control. Also values for the duration of the start-up process h...

2020 21st International Symposium on Electrical Apparatus & Technologies (SIELA), 2020

The wide range of differences in conditions (temperature, pressure, humidity, vibrations, radiati... more The wide range of differences in conditions (temperature, pressure, humidity, vibrations, radiation) for communication equipment leads to hard demands towards the tolerances of the input parameters of the compound electronics circuits. The mentioned demands in case of electronic circuits are maintained with reducing of the tolerances of the functional elements mainly and using of new technical solution, which to give minimum influence of the destabilizing factors. The second method is much more perspective. In such a case this way gives an manual for establishing of an optimum technical decision for designing of communication equipment and an example how to use it.

This report presents a new structural design of the control channel for the mainstream traction m... more This report presents a new structural design of the control channel for the mainstream traction modulus. The linear part of which determines both the dynamics of the system and the component of the stator current. It is shown the transfer function of the structural scheme as a whole and there are introduced cross-links. It is also shown a structural scheme for direct compensation of the cross-links. It is proposed a structural diagram of the electric drive system while taking into account the angular error of the support coordinate system.