Lesson 1 Chapter Six
AC to AC Voltage Converters
This lesson provides the reader the following:
(i) AC-AC power conversion topologies at fixed frequency
(ii) Power converter options available for the conversion
(iii) Ability to formulate equations describing the current waveform for the PAC
(iv) Ability sketch the current waveform by observation of the circuit
(v) Ability to assess the performance of the converter of the topologies
A power electronic ac–ac converter, in generic form, accepts electric power from one system and converts it for delivery to another ac system with waveforms of different amplitude, frequency, and phase. They may be single- or three-phase types depending on their power ratings. The ac–ac converter employed to vary the rms voltage across the load at constant frequency are known as ac voltage controllers or ac regulators The voltage control is accomplished either by (i) phase control under natural commutation using pairs of silicon controlled rectifiers (SCRs) or triacs or (ii) by on/off control under forced commutation/ self-commutation using fully controlled self-commutate switches like gate turn-off thyristors (GTOs), power transistors, integrated gate bipolar transistor (IGBTs), MOS controlled thyristors (MCTs), integrated gate commutated thyristor (IGCTs), etc.
The ac–ac power converters in which ac power at one frequency is directly converted to ac power at another frequency without any intermediate dc conversion link (as in the case of inverters) are known as cycloconverters, the majority of which use naturally commutated SCRs for their operation when the maximum output frequency is limited to a fraction of the input frequency. With rapid advancements of fast-acting fully controlled switches, forced commutated cycloconverters, or recently developed matrix converters with bi-directional on/off control switches provide independent control of the magnitude and the frequency of the generated output voltage as well as sinusoidal modulation of output voltage and current.
While typical applications of ac voltage controllers include lighting and heating control, online transformer tap changing, soft-starting and speed control of pump and fan drives, the cycloconverters are mainly used for high power low speed large ac motor drives for application in cement kilns, rolling mills, and ship propellers. The power circuits, control methods and the operation of the ac voltage controllers, cycloconverters, and matrix converters are introduced in this chapter. A brief review is also made regarding their applications.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .