Single-phase mid-point controlled rectifier with RL load :
The circuit configuration of single-phase midpoint controlled rectifier is shown in the figure. During positive half-cycle of input supply voltage, terminal “a” is positive w.r.t. terminal “n” and “n” is positive w.r.t. terminal “b”. Thyristor T1 is therefore forward biased whereas the thyristor T2 is reverse biased. Hence during positive half-cycle of input supply voltage, gate pulse is applied to T1. When T1 is fired, it acts as short-circuit and input voltage Van appears across load. The thyristor T1 conducts till its current falls to zero. Due to inductive load, current lags behind the voltage and falls to zero after reversal of voltage. Thus some part of next negative half-cycle of voltage can appear across load. During negative half-cycle of input voltage, terminal “b” becomes positive w. r. t. terminal “n” and “n” becomes positive w.r.t. terminal “a”. Thyristor T1 is therefore reverse biased whereas the thyristor T2 is forward biased. Hence during negative half-cycle of input supply voltage, gate pulse is applied to T2. When T2 is fired, it acts as short-circuit and input voltage Vbn appears across load. The thyristor T2 conducts till its current falls to zero. Due to inductive load, current lags behind the voltage and falls to zero after reversal of voltage. Thus some part of next positive half-cycle of voltage with reversed polarity can appear across load.