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ac/ac Converters
Published in K Sundareswaran, Elementary Concepts of Power Electronic Drives, 2019
A cycloconverter is an ac/ac power converter supplied from fixed-frequency, fixed-voltage ac mains and provides a lower frequency ac voltage at the output. A bridge-type cycloconverter is shown in Fig. 8.9. Here, there are two ac/dc converters labeled as C-1 and C-2. The operation of the circuit can be explained with the help of waveforms depicted in Fig. 8.10. Here Fig. 8.10(a) shows the supply voltage waveform, and C-1 is gated for the one cycle of vs, and C-2 is made to conduct for the second cycle; if this sequence continues, the output voltage appears as shown in Fig. 8.10(b) and the output frequency is now f1/2. The waveforms in Fig. 8.10(c) shows the output frequency at f1/3. Output voltage control can be achieved by implementing phase angle control on C-1 and C-2, leading to variable-voltage, low-frequency output voltage as given in Fig. 8.10(d). Cycloconverters are used for low-speed operation of ac motor drives.
Power Electronics
Published in Mohd Hasan Ali, Wind Energy Systems, 2017
Typical applications of a cycloconverter include to control the speed of an AC traction motor and to start a synchronous motor. Most of these cycloconverters have a high power output—on the order of a few megawatts—and silicon-controlled rectifiers (SCRs) are used in these circuits. By contrast, low-cost, low-power cycloconverters for low-power AC motors are also in use, and many such circuits tend to use TRIACs in place of SCRs. Unlike an SCR, which conducts in only one direction, a TRIAC is capable of conducting in either direction, but it is also a three-terminal device. The use of a cycloconverter is not as common as that of an inverter, and a cycloinverter is rarely used. However, it is common in very high-power applications such as for ball mills in ore processing, cement kilns, and azimuth thrusters in large ships.
Power Electronics
Published in Mukund R. Patel, Omid Beik, Wind and Solar Power Systems, 2021
The cycloconverter, a direct frequency changer, converts AC power of one frequency to AC power of another frequency by AC–AC conversion. By adding control circuitry capable of measuring the voltage and frequency of the bus bar and by comparing them with the desired voltage and frequency, we can obtain a constant voltage and frequency output. The cycloconverter used to be more economical than the DC-link inverter but has been gradually replaced by the rectifier–inverter setup because of its high harmonic content and the decreasing price of power semiconductors. However, advances in fast switching devices and control microprocessors are increasing the efficiency and power quality of the cycloconverter.
Overview of High-Step-Up DC–DC Converters for Renewable Energy Sources
Published in IETE Technical Review, 2018
Subhransu Padhee, Umesh Chandra Pati, Kamalakanta Mahapatra
One of the other kind of PCU topologies proposed by [11–13] comprises of full-bridge DC–AC inverter, high-frequency step-up transformer, and two forced AC–AC cycloconverter. The cycloconverter is line switched which reduces the switching losses. The high-frequency transformer is used to reduce the switching loss of inverter. The power circuit of the PCU using DC–AC inverter and AC–AC cycloconverter is shown in Figure 5. Table 1 provides the comparative analysis of different PCU topologies discussed in Section 2.
Selective Harmonic Elimination in Space Vector Modulated AC–AC Converter Using FPGA
Published in Electric Power Components and Systems, 2022
Anshul Agarwal, Abhishek Awasthi, Vinay Kumar Jadoun, Ramesh C. Bansal
Simulation is performed for a cycloconverter at varying modulation indexes and a fixed output frequency of 150 Hz. THD comes out to be 12.5% when the modulation index, m = 0.2. With an increase in the modulation index, at m = 0.45, THD is found out to be the least at 8.5%, as shown in Figure 5(a).