Leos Beran

Thermal effect of short-circuit current in low power induction motors

Diagnostic of reliability of induction motors (IM) is very important for industry. The article deals with the analyse of short-circuit currents in stator winding of low power induction motors which can strongly affected reliability of IMs. The occurrence of short-circuit arises when some parts of the insulation system of a stator winding breakdown. The stator winding loses a part of active coil and its inductivity decreases. The short-circuit current warms up the surrounding stator winding with its heat effect at point of the short-circuited stator winding. Theoretical part describes two models to simulate different short-circuits that can occur in the stator winding. The first model is a single-phase linear model and the second is a numerical model in SymPowerSystems Toolbox of Matlab software. Chapter III analyses thermal activity on separate parts of the stator winding. Thermal effects were verified on a set up model that consists of a specially designed experimental motor (EM) with the temperature monitoring in slots of the stator.

Electric drives and laboratory facilities for its education

Students of electrical engineering need to obtain practical abilities and skills from electric drives branch to acquire inside the theory better. Experience from last years shows that students have problems to understand basic physical principles of electric machines. The introduced modern educational facility should improve this adverse situation.

Global data structure for positioning machine controlled by PLC

Well designed data structure simplifies programming of complex systems and makes its application more efficient. The issue in proper data structure declaration in programmable logic controller (PLC) is what technique for describing parameters, commands and states of system to choose. For universal system implementation its data structure should be expandable according to the requirements of controlled application. This paper describes universal global data structure for driving multi-axis positioning machines or manipulators by B&R programmable logic controller (PLC). It is defined by hierarchically composite structure data types which can be used in all programs and parts of software. It consists of three main substructures in which PLC, motion and main program parameters, commands and state machines are described. Global structure can be transformed to control various systems which support PLCopen standard.

Single-phase induction motor noise caused by improper manufacturer design

Single-Phase induction motors are used in simple industrial applications very often. This article deals with a singlephase motor fan used in heating system of industry buildings. Single-phase distribution of electricity is cheaper and simpler. However, it brings some disadvantages in using electric machines such as induction motors. The analysis shows problems of using slip to control velocity by supplying voltage. Bad design of both auxiliary and main winding together with capacity control can produce noise that is not acceptable in an application of heating systems. The effect of the bad design is presented in this paper. The possibility of velocity control from a variable frequency power supply is discussed as well.

Development of a robotic arm suitable for demonstration of advanced control methods

Our article deals with the development of a robotic arm with “open control system” (for this particular application — with two degrees of freedom and possibility to add). The open control system allows, together with the known parameters of our robotic arm, to use advanced control methods. The robotic arm is controlled by a PLC and automatically generated code via tools — BR Target for Simulink. This tool allows us to convert Simulink models into an automatically generated code in C/C++ and its direct implementation on PLCs. This method of a design allows an easy implementation for sophisticated simulation models and control structures. The article focuses on the preparation and evaluation of the properties of a robotic arm for implementation possibilities of advanced control methods. At first, we found the physical limitations of the individual actuators. Then we dealt with the problems of generating the trajectory with respect to the physical limitations of the individual actuators. For the dynamics of the robotic arm spline functions for trajectory generation and performed measurements of lag errors are used. In conclusion, we evaluated the advantages and disadvantages of this method of control and outlined possible applications for which we can apply this kind of control.

The implementation of CNC control using smart device controller

This paper describes the design of a medium size three-axis manipulator. The implementation of CNC control is also presented. The equipment has been designed and produced for the purpose of CNC systems teaching based on the electrical drives. The basis for the control system is an industrial computer. The Module with PWM outputs supplies the power to the drives of all three axes which have DC motors. The drive implementation is realized using the Smart Device Controller (SDC). The CNC system implementation into the facility is done on the software basis. This eliminates the need for additional special hardware which would ensure the operation of NC functions. In terms of hardware, the advantage is simple and relatively cheap solution at a professional level. SDC structure allows develop hardware independent CNC machine.