Single phase fully controlled halfwave rectifier with R-L Load - circuit Diagram & waveforms
Single phase fully controlled half wave rectifier with RL load:
- This configuration is hardly used in practice.
- As in the case of a resistive load, the thyristor T becomes forward biased when the supply voltage becomes positive at ωt = 0. However, it does not start conduction until a gate pulse is applied at ωt = α. As the thyristor turns ON at ωt = α, the input voltage appears across the load and the load current starts building up.
- Unlike a resistive load, the load current does not become zero at ωt = π, instead it continues to flow through the thyristor and the negative supply voltage appears across the load forcing the load current to decrease.
- At ωt = β (β > π) the load current becomes zero and the thyristor undergoes reverse recovery. From this point onwards the thyristor starts blocking the supply voltage and the load voltage remains zero until the thyristor is turned ON again in the next cycle. The value of β depends on the load parameters.
- Unlike the resistive load the average and RMS output voltage depends on the load parameters. Since the thyristors does not conduct over the entire input supply cycle this mode of operation is called the “discontinuous conduction mode”.
- IORMS cannot be obtained from VORMS directly. For that a closed from expression for i0 will be required. The value of β in terms of the circuit parameters can also be found from the expression of i0.
- We can obtain IORMS as well as β.