18-12-2017, 10:13 AM
A cycloconverter (CCV) or a cyclo inverter converts a constant voltage, constant frequency AC waveform to another AC waveform of a lower frequency by synthesising the output waveform of segments of the AC supply without a DC link intermediate (Dorf 1993, pp. 2241-2243 and Lander 1993, p.181). There are two main types of CCV, type of circulating current or blocking mode, most high-power commercial products are of the blocking mode type. SCR switching devices controlled by phase can be used throughout the CCV range, low cost and low power consumption. TRIAC-based CCVs are inherently reserved for resistive load applications. The amplitude and the frequency of the output voltage of the converters are both variables. The output ratio at the input frequency of a three-phase CCV must be less than about one third for CCVs in circulating current mode or half for CCVs in blocking mode. (Lander 1993, p.188) The quality of the output wave improves as the pulse number of the switching device jumpers in the phase shift configuration increases at the CCV input. In general, the CCV can have input / output configurations of 1 phase / 1 phase, 3 phases / 1 phase and 3 phases / 3 phases, but most applications are three phase / three phase.