Petr Prochazka

Maximum efficiency of an induction machine operating in a wide range of speed and torque - part 1 (theoretical analysis)

A set of unique equations usable to calculate directly the optimum slip frequency and line voltage of a 3phase squirrel-cage induction machine with respect to maximum efficiency is deduced in this article. An operation in steady state at any requested speed and torque in a wide range is taken into consideration. The proposed calculation is especially useful for independent traction purposes. The requested torque, speed and an extended mathematical model of the machine based on a Γ-network are the inputs of the calculation. The optimum slip frequency and line voltage are the outputs. The calculation results using the deduced analytical formulas were verified with a practical measurement and with a MATLAB simulation. Due to the extensiveness of the problems the correspondence of the theoretical calculation with the practical results will be presented in a separate 2nd part of the article.

Design of small electric car

Paper deals with design of traction drive for small electric car where its primary energy source is realized by two hydrogen cells with nominal power 2 × 1,2 kW. Main attention is paid to find appropriate torque-velocity, resp. power-velocity dependences related to wheel of the small electric car. According to these characteristics an appropriate gear ratio is calculated. Finally, an appropriate traction motor is chosen.

Simulation modelling of MEMS thermoelectric generator for aircraft applications

This paper deals with a simulation modelling of a thermoelectric energy harvester for aircraft applications. The aim of this paper is to provide overview of simulation modelling methods, which are used in development process of the autonomic thermoelectric energy harvester. The assumed harvester is based on MEMS technology and is capable to operate as an independent energy source under high range of operational condition required by aircraft applications.

Mathematical tool for RMS value calculation of impulse signals

The article deals with the special mathematical method with the help of which it is possible to calculate the RMS value of arbitrary voltage or current PWM impulses occurring in power electronics. Impulses may have continuously variable duty cycle as well as continuously variable top and bottom covers. The tool is suitable predominantly for the analysis of voltage and current impulses occurring in power converters working in sinusoidal PWM mode.

Small electric vehicle drive control according to maximal efficiency criteria

This paper deals with induction drive control implementation according to the requirement of maximal efficiency for a traction application in a small electric car. Optimum setting of the motor slip frequency was found according to the criteria of maximal motor efficiency in a wide range of torque and speed (see [1] and [2]). The traction drive is an application without any extreme dynamic response requirement. It is possible to use scalar control strategies without any significant impact on the vehicle dynamic behavior. An implementation of the optimum motor setting into a scalar control is described in this article. Optimum rotor frequency and stator current look-up tables for any operating point in the used range of desired torque and actual speed were generated and used in common induction machine scalar control schemes.

Maximum efficiency of an induction machine operating in a wide range of speed and torque - part 2 (calculation, simulation and measurement results)

A set of equations usable to calculate directly the optimum slip frequency and line voltage of a 3phase squirrel-cage induction machine with respect to maximum efficiency was deduced in part 1 of this article. An operation in steady state at any requested speed and torque in a wide range is taken into consideration. The requested torque, speed and an extended mathematical model of the machine based on a Γ-network are the inputs of the calculation. The optimum slip frequency and line voltage are the outputs. The calculation results using the deduced analytical formulas are compared with practical measurement results and with a MATLAB simulation of the machine input power in this part 2 of the article.

Measurement of Power Transistors Dynamic Parameters

This article deals with analysis of switching processes of power transistor as well as with description of performed measurement methods of these dynamic processes. The results are demonstrated on power IGBT transistor, nevertheless the measurement methods are valid for all power devices in general. Due to the fact, that the extremely dynamic and power processes have to be analyzed, then the special measuring laboratory workplace (MLW) was developed for proper oscillographic measurement of these processes. Further, the current sensor with ultra-wide bandwidth has to be developed. Description of the MLW is presented in this paper together with its development process. This paper gives the complex methodology for analysis of power devices switching processes.

Speed Estimator for Low Speed PMSM Aerospace Application

The paper is focused on development of low speed PMSM direct drive application. The high resolution of position setting (18 bits per revolution) is demanded at very low speed about 10 RPM. The quantization of speed controller error cause unaccepted torque ripple. The digital filters reduce dynamic of speed control loop therefore, the speed estimator has to be employed to reduce torque ripples without reduction of speed control performance. The application is intended for demanded aerospace application. The paper describes design of speed estimator with cooperation of vector controlled PMSM motor. The Simulink model is realized to verify the proper operation of whole drive application and simulation results are presented in this paper.

Induction Machine Models and Equivalent Circuits Based on Hybrid Parameters of Two-Port Network

The paper is focused on development of induction machine (IM) model based on general two-port network theory, which is elemental theory well-known for all electrical engineers. Since the theory of IM is more specialized and known for engineers with some expertise in the field of electrical machines and drives. Application of the two-port network theory on IM can clarify the development process of IM model or eventually equivalent circuit for wide area of electrical engineers. The whole building process is also based on analogy with transformer and the theory of rotational coordinates is also employed. The models and equivalent circuits are then more suitable for understanding physical principles of IM from macroscopic point of view.

Dynamic Model of Wye Connected Induction Machine

The paper deals with a derivation of a dynamic model of induction machines with wye connected stator and rotor windings. The mathematical modeling of any electric machine is an inseparable part of the knowledge of any future/present engineers involved in the control of the electric drives. In the paper, several models of the induction machines are derived in a comprehensible way with an emphasis on structural and parameter integrity of all models. Derived dynamic model with line-to-line stator voltages presents a simple substitution to more general but also more complicated natural model of induction machines.