Single Phase to Single Phase Bridge Configuration Cycloconverter
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Introduction
The center tapping transformer is not required in this configuration.
The SCR T1 to SCR T4 works as positive group ( P – converter ) and SCR T5 to SCR T8 works as negative group ( N – converter ).
If the P – converter and N – converter conducts simultaneously, the supply is short circuited.
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It should be noted that when P – group SCRs conducts, the N group SCRs remains in off condition and vice versa.
The output voltage becomes symmetrical if the firing angle of the both converter SCRs are kept same.
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Working : Positive Group
The SCR T1 and SCR T3 are turned on during positive half cycle of the alternating supply resulting load current flows through path A – SCR T1 – LOAD – SCR T3 – B.
The SCR T1 and SCR T3 naturally turns off due to negative half cycle of the alternating supply.
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When SCR T2 and SCR T4 are turned on, the load current flows through path B – SCR T2 – LOAD – SCR T4 – A.
The load current flows through supply to load during positive half cycle of the alternating supply.
There are two positive half cycle at the output due to one positive and one negative half cycle of the alternating supply.
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Working : Negative Group
The SCR T5 and SCR T7 are turned on during positive half cycle of the alternating supply and load current flows through path A – SCR T7 – LOAD – SCR T5 – B.
The direction of load current in the N – converter is opposite to that of current flow in the P – converter.
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The SCR T5 and SCR T7 naturally turns off due to negative half cycle of the alternating supply.
When SCR T6 and SCR T8 are turned on, the load current flows through path B – SCR T8 – LOAD – SCR T6 – A.
The direction of load current reverses and there are two negative half cycle at the output due to one positive and one negative half cycle of the alternating supply at the input.
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Waveform Analysis
The input and output waveforms of the bridge configuration cyclo converter is shown in the figure.
When there are two complete cycles at the input sides, there is only one complete cycle at the output side resulting we can say that the output frequency is one half to that of input frequency.
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If the input frequency is 50 Hz, the output frequency will be 25 Hz.
The waveform of the output voltage is adjusted by adjusting firing angle of the SCRs.