Abstract
In this study, power quality coefficients that determine the distortion of electrical systems are established. The power factor is chosen as a universal criterion for electromagnetic and electro-energetic compatibility of distorted sources and distorting loads. Mathematical expressions are obtained for its calculation in various cases of electrical systems distortion. As an application example, power balances and power factors of a variable frequency asynchronous drive system are considered. The criterion: the power factor not only determines the energy and electromagnetic compatibility of the drive with power supply, but it also evaluates drive efficiency. Experimental studies were carried out under usage of inexpensive, commonly used measuring devices both on the grid side of the frequency converter and on the asynchronous motor side. The studied coefficients were determined in two ways: measuring instruments and analysis of oscillograms. The second method for determining the above coefficients from oscillograms of currents and voltages also requires finding the total harmonic distortion (THD) of currents and voltages for the corresponding load adjusting points. The similarity of the obtained results shows that both of these methods can be applied. According to the operating mode of the load, the criterion is calculated as an average range in a certain range of speed control, or it is determined by considering a given tachogram of speed changes. The results of experimental studies confirm the correctness of the theoretical provisions.
Highlights
The widespread use of power converting equipment and the presence of powerful partial phase loads lead to a distortion of the consumption mode, which, in general, are caused by asymmetry, imbalance, and nonlinearity of the load
The distortion of three-phase systems is characterized by power quality indicators, which include the following coefficients: voltage ε U and current ε I unbalance: voltage ε 0U and current ε 0I lack of balance: and total harmonic distortion (THD) of voltage and of current
The results of calculating the power factors and offset and harmonic distortion THDs, Measurement which were obtained by measuring instruments and by analyzing oscillograms using Parameter
Summary
The widespread use of power converting equipment and the presence of powerful partial phase loads lead to a distortion of the consumption mode, which, in general, are caused by asymmetry, imbalance, and nonlinearity of the load. The presence of high-order voltage time harmonics on the terminals of the induction motor, as well as the higher spatial harmonics generated by them, leads to an increase in electrical and magnetic losses, excessive heating, and a decrease in productivity [23] To determine these parameters, information on motor equivalent circuit for the entire harmonics spectrum when supplying the stator windings is Modern semiconductor frequency converters with IGBT transistors allow realizing the most rational control pulse-width modulation. Oscillograms look similar at other frequencies and loads Their spectral analysis was carried out, and the coefficients of non-sinusoidal current and voltage distortions for the grid and motor sides were determined (Figure 3). The power factors and the phase shift of the fundamental harmonic at the motor input are considered for a distorted system with non-sinusoidal distortions of currents and voltages (18). The results of calculating the power factors and offset and harmonic distortion THDs, Measurement which were obtained by measuring instruments and by analyzing oscillograms using Parameter
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
