Single Phase AC Voltage Controllers - Power Electronics

What are Single Phase AC Voltage Controllers?

Single-phase AC controller (voltage controller) can be used for differentiating the alternating voltage value when it is applied to a load circuit. A thyristor will also be placed among the load and the constant source of AC voltage.

Root mean square alternating voltage can be synchronized by modifying the thyristor triggering angle. During this stage of phase control, thyristors will be engaged as switches for establishing a connection between AC input supply and the load circuit at the time of each input cycle. For every positive input voltage, chopping will occur and voltage will be decreased.

Circuit Diagram with a Resistive Load


During half part of the cycle, thyristor switch will be turned ON for enabling the voltage input so that it appears across the load. This will be followed by the OFF state at the time of the last half cycle in order to disconnect the load from the source voltage.

While controlling the triggering angle α, voltage RMS value on the load will also be controlled. Triggering angle α can thus be defined as the value of ωt at which the thyristor switches ON.

Multistage Sequence Control of AC Converter

While controlling two or more sequence control stages, there can be an enhancement in power factor and additional reduction in THD (total harmonic distortion). An n-stage sequence control converter will have n windings in the transformer secondary part with each rated es/n (the source voltage).

Zero sequence way will be created When two AC converters are located parallel to each other. Minor difference between the two converters can cause a great zero sequence in the circulating current. Below diagram shows the parallel system of a converter and the direction of the current will be anti-clockwise with regard to that of the voltage system.


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