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The paper describes the effects of changes in the triggering frequency on the maximum working frequency of a series inverter. Inverters differ in the type of load and in the mutual coupling existing between two commutation inductors in the circuit. It has been shown that the transient state is a result of changes in thyristor commutation from natural or critical to overlapping, and is dependent on the mode of change of the triggering frequency. The region of overlapping commutation has been determined by using two types of frequency change: fast (by keying modulation) and slow (by frequency modulation). The results show that slow changes in thyristor commutation permit a higher maximum working frequency than do fast changes. The region of overlapping commutation of thyristors is defined by new limit curves. The results may, for example, be applied in the design of an ultrasonic generator operating with frequency modulation. [ABSTRACT FROM AUTHOR]

The paper presents the results of theoretical analysis as well as numerical calculations of the maximum output frequency in a series inverter working with overlapping commutation of the thyristors. The changes from natural or critical thyristor commutation to overlapping commutation were fast. The region of overlapping commutation is limited by new extreme curves which ave dependent on the type of load as well as on the mutual coupling value between the two commutation inductors. Resonance shaping load-current edges have also been considered in this paper. [ABSTRACT FROM AUTHOR]

Analyzes a single phase current source inverter feeding an inductive load. Design criteria for the inverter; Proportion between the necessary commutating capacitance and the square of turn-off time of the thyristors; Circuit operation for higher frequencies.

The three-phase stepped-wave inverter is based on a new method of synthesizing waveforms. The proposed system comprises a 120° conduction type three phase bridge inverter and a single-phase triple-frequency square-wave inverter. The triple-frequency inverter used for wave-shaping is of low power and is used in the neutral circuit of the three-phase inverter. A special complementary impulse commutation circuit realizes the above system with only eight thyristors. The output voltage waveform has three steps per quarter cycle and has a total harmonic distortion of 15-1%. The kVA ratings of the wound components are derived. The experimental results are presented and discussed. [ABSTRACT FROM AUTHOR]

Discusses the simultaneous elimination of undesirable harmonics and output voltage variation in a pulse-width modulated inverter. Advantages of the sinusoidal modulation technique and the Patel-Hoft method; Relationship between the actual load voltage waveform and phase shift angle; Causes of variation in phase shift between the triggering signals applied to the half-bridge inverters.

Presents the state-of-the art developments in the sequential-switching high-power high-frequency inverter using reverse-blocking thyristors. Control implementation of the inverter on the basis of induction heating and melting applications; Description of fast-response power regulation and parallel tuned frequency tracking strategies; Use of state-variable clamped action.

In this paper the influence of the dynamic parameters of real thyristors on the properties of series inverters operating in the region of overlapping commutation has been presented. The formal SCR model has been used based on the rise time (t[sub r]) characterizing the thyristor turn-on process and on the reverse recovery time (t[sub rr]) and the total stored charged (Q[sub rr]) characterizing the thyristor turn-off process. [ABSTRACT FROM AUTHOR]