Subject : Power Electronics
Unit : AC to DC Converters
Single phase half controlled converter in the discontinuous conduction mode
Single phase half controlled converter in the discontinuous conduction mode (a) π – θ ≤ β ≤ π (b) π ≤ β ≤ π α :
When T1 is fired at ωt = α the output voltage (instantaneous value) is larger than the back emf. Therefore, the load current increases till vo becomes equal to E again at ωt = π – θ. There, onwards the load current starts decreasing. Now if io becomes zero before T3 is fired at ωt = π α the conduction becomes discontinuous. So clearly the condition for continuous conduction will be i0|ωt= α≥0
Therefore,
or,
- When this equation doesn’t hold good, the conduction becomes discontinuous.
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When the conduction becomes discontinuous two cases arises.
- π – θ ≤ β ≤ π
- π ≤ β ≤ π α
- In the case of (π – θ ≤ β ≤ π),
V0= Vi for α ≤ ωt ≤ π
V0 = 0 for π ≤ ωt ≤ β
Vo = E for β ≤ ωt ≤ π α