Behavior of Transistor Switching in AC Chopper Circuit

In this paper, an AC chopper circuit, using a power transistor, is described which chops the AC voltage with a commercial frequency. The circuit is composed of a diode bridge and a power transistor in series with a load and capable of adjusting the switching frequency, fc, and the time ratio, T=ton/(ton+toff). The switching frequency and the time ratio of the AC chopper circuit depend on switching-times, that is, delay time, rise time, carrier storage time and fall time, especially in the high frequency. The upper limit of the switching frequency (about 150kHz) and the output characteristics of the circuit are investigated

Influence of Magnetic Saturation of Iron-Core on Performance of Thyristor Phase Control Circuit

The influence of magnetic saturation of iron-core on the performance of thyristor phase control circuit with series RLC elements is described. The circuit is analyzed by applying an approximate model of three straight lines to the flux Φ vs. current i curve of the iron-core reactor. And the influence on waveforms, r.m.s. values, power factor and response are discussed

Analysis of a HaIf-Controlled Single-Phase Bridge Circuit with Free-Wheeling Diode (II)

This paper is presented on the operation of the phase controlled single-phase bridge circuit with a free-wheeling diode, which has capacitance in parallel with the inductive load. Such circuit configuration is frequently met with, for instance, at the time when the more smoothness of d-c voltage is required, the higher reliability of SCR's firing is taken into account or load windings include some capacitance which is not negligible. The capacitance influences not only largely upon SCR's rush current but also significantly upon control characteristics of the circuit such as wave forms, pulsating ratio and power factor etc. Here, the various effects of the capacitance on the circuit performance are discussed

Analysis and Design of Parallel Inverter Circuit with Parallel Inductive Load

In this paper, the parallel inverter circuit with the load consisted of resistive load and constant reactive load in parallel, is analyzed taking into acourlt the d-c source reactance. The circuit has a good voltage regulation for the variation of resistive load current, except the vicinity of no load. The design method in using the results of analysis is also discussed

Analysis of Brushless-dc Motor Drive System Taking Account of a Load

In the power converter of ac drive system the switching behavior of semiconductors causes the distorted voltage and current waveforms, thus the drive characteristics are affected by them. It is, especially, an essential problem that the distorted current waveforms induce the torque ripple. It is assumed in the previous analysis that the input voltage of inverter is a ripple-free dc one. In industry, however, the input voltage of inverter is gained by rectifying the ac voltage. The torque ripple is caused by not only the behavior of inverter but also the behavior of converter. It is required to develop the analysis taking account of the both behaviors. In this paper, the analysis of brushless-dc motor drive system is proposed taking account of the ac supply, power converter, motor and load. This analytical method is the most suitable one for the analysis of practical system. The effects of factors, e.g. filter constants, inverter frequency, phase relation between ac supply and inverter cycle, load and inertia on the speed variation are revealed by this analysis. Further, the decision of filter constants is discussed from a view of speed variation

AC Chopper Circuit with Lagging Reactive Load

An ac chopper circuit, which chops an ac voltage in a complete cycle for any lagging reactive load, is devised. The circuit is constructed of two ac-switches composed of power transistors and diodes. The load voltage is smoothly controlled by varying the time ratio of ac-switch. Transistors operate in a highfrequency chopping mode, thereby the ripples of the source current and the load current are easily filtered. Furthermore the input power factor of this model is better than that of the thyristor phase control circuit. In this paper, the construction and the driving method of this model are described

Analysis of a Half-Controlled Single-Phase Bridge Circuit with Free-Wheeling Diode (1)

The operation, mainly in a steady state, of a half controlled single-phase bridge circuit with a finite inductive load, has been treated analytically. Some operation features of particular bridge circuits are discussed

Analysis of Thyristor Phase Control Circuit with Parallel Resonance Elements

The phase control characteristics in a thyristor phase control circuit with parallel resonance elements indicate very interesting phenomenon. Several extreme values appear on the phase control curve. The phenomenon is different from the step-up one in a thyristor phase control circuit with series RLC elements which is interpreted as series resonance. To comprehend the circuit performance with those loads, it is necessary that the phenomenon on extreme value is physically clarified from other viewpoints. In this paper the performance in this circuit is studied from two viewpoints of a natural oscillation and a parallel resonance. Then, it is found that the performance depends on a natural frequency in thyristor conducting period and a parallel resonance frequency in thyristor non-conducting period. Therefore, the interesting phenomenon on extreme value is affected by the alternative of natural frequency or parallel resonance frequency

Generalized Analytical Program of Thyristor Phase Control Circuit with Series and Parallel Resonance Load

The systematic analytical method is reqUired for the ac phase control circuit by means of an inverse parallel thyristor pair which has a series and parallel L-C resonant load, because the phase control action causes abnormal and interesting phenomena, such as an extreme increase of voltage and current, an unique increase and decrease of contained higher harmonics, and a wide variation of power factor, etc. In this paper, the program for the analysis of the thyristor phase control circuit with a series and parallel connected load of series R-L-C circuit units, is been developed. By means of the program, the transient and steady state characteristics of the circuit can be calculated and then comparative study of various versions of circuits can be carried out systematically. The usefulness of the program is demonstrated by some numerical calculated examples

A Modified Type of the Resonant Turn-off SCR D-C Chopper

A modified type of the resonant turn-off d-c chopprr using an auxiliary SCR, compared with its conventional one, has no limitation about its starting and also operates more steadily. Presented in this paper, making a comparison between the modified type and the conventional one, are the circuit analysis and its efficiency measurement from the point of view of overall efficiency, that is, the ratio of the output to the input. Furthermore, some effects of the source impedance, counter emf load, etc. are discussed. As a result, it has been analytically clarified that this modified type is different from the conventional circuit only by one terminal connection of turn-off capacitor, but has the features of uncompounded circuit configuration, no limitation about its starting and more steady operation