Radoslav Cipin

Harmonic reduction in induction machine using slot wedges optimization

The time and the space waveform of electric and magnetic magnitudes of AC machines are a non-sinusoidal including the case of powered by the grid. The reasons of the deformation are in the actual design layout of electrical machines, at various asymmetry generated in the production or as a result of failures in electric, magnetic and mechanical parts of the machine. The rotating electric machine may produce several types of harmonics. Some may be suppressed by construction modifications (skewing slots, magnetic conducting slot wedges, the air gap increasing and the winding pitch reducing). Many of these modifications are often not each other exclude or inconsistent with other requirements of the machine. Therefore, these harmonics cannot be completely suppressed. The possibility way how to reduce harmonics of induction machine using slot wedges optimization is presented.

New infinitesimal method for the analysis and synthesis of AC machines winding

The paper describes a new universal infinitesimal method which enables the analysis and synthesis of arbitrary AC motor windings. The method is based on the notion of the local angular density of conductors n(α) = dN(α)/dα. It will be proved the proportionality B(α) ≈ ∫n(α)dα for the magnetic flux density in the air gap. The function n(α) can be arbitrary, i.e. of continual or impulse character. In a special case, when the function n(α) is given in the form of Dirac impulses, this new method generates the same results as the classical method. Spatial functions n(α), B(α) may be evolved into Fourier series. The first harmonic components of these functions serve to the electromagnetic design of the induction or synchronous motor. Higher harmonic components serve to the calculation of the differential leakages. New method enables to calculate linkage fluxes, and self as well as mutual inductances of any stator and rotor windings, too.

New infinitesimal method for the calculation of self and mutual inductances of arbitrary AC windings

The paper describes a new universal infinitesimal method, which enables the calculation of self and mutual inductances of arbitrary AC windings. The method is based on the notion of the local angular density of conductors n(α) = dN(α)/dα. It will be proved the proportionality B(α)≈ ∫n(α)dα for the magnetic flux density in the air gap. The function n(α) can be arbitrary, i.e. of continual or impulse character. Spatial functions n(α), B(α) may be evolved into Fourier series. The first harmonic components of these functions serve to the electromagnetic design of the induction or synchronous motor. Higher harmonic components serve to the calculation of the differential leakages.

Skin effect in rotor bars of induction motor in form of transfer function

This article deals with a modeling of a skin effect in rotor bars of an induction motor. Frequency dependencies of rotor resistance and leakage inductance are calculated based on a static model of an induction motor in form of a Gamma-circuit. A skin effect is modeled by a transfer function. There is comparison of transfer function created for theoretical values and for measured one. There is shown that a transfer function has similar form in both cases. Created transfer function can describe dependency of rotor resistance and leakage inductance on frequency very precisely.

Identification of the induction motor parameters based on the acceleration method

The paper deals with identification of the equivalent circuit parameters of the induction motor. The identification has been done by comparison of measured torque and current characteristics and computed torque and current characteristics. Equivalent circuit of the induction motor has been used in form of the Γ-circuit. There is computed the dependency of the leakage inductance and the rotor resistance on the slip. For exact identification of the motor parameters has been used the genetic algorithm.

Electromagnetic design of irregular three phase windings

The paper deals with the design of irregular AC windings by a new method. The new method is based on the notion of “local density of conductors”. Design of the interspersed winding 1-3-1 is shown as an example of using this new method. This type of winding can be used to reduce higher harmonic components of magnetic flux density in the air gap, mainly the fifth and the seventh harmonic. This new method can be used for any three-phase windings even for arbitrary irregular windings with different number of conductors in individual slots.

Fractional-Order Model of DC Motor

This article deals with application of fractional calculus in a model of a DC motor. The basic assumption of fractional calculus is that the classical derivative can be generalized to non-integer one. The basic definitions of fractional calculus are presented. The fractional model of DC motor is simulated by a numerical scheme based on a Grunwald-Letnikov derivative. Possible usage of fractional calculus is shown for modeling a friction in electric machines.

AC fractional winding design by the new method

The paper deals with the of AC fractional windings design by the new method. The new method is based on the local density of conductors. The local density of conductor describes distribution of conductors of the whole winding in the slots. By the new method, it is simple to analyze and design any fractional winding. On example of simple fractional winding, it is shown using of this new method for calculation the total winding factor that is used to design of windings by classical method.

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.

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.