1. Three-phase Rectifiers

2. Rectifiers (SEE 4433) Half wave Uncontrolled (diode) Controlled (SCR) Uncontrolled (diode) Controlled (SCR) Full wave Single-phase Three-phase Uncontrolled (diode) Controlled (SCR)

3. At any one time, only ONE of the lower diodes can conduct The most forward biased diode will conduct – this will depend on the instantaneous phase voltage since the lower diodes have a common anode At any one time, only ONE of the upper diodes can conduct The most forward biased diode will conduct – this will depend on the instantaneous phase voltage since the upper diodes have a common cathode Uncontrolled (diode) Three-phase Rectifiers

4. At any one time, only ONE of the lower diodes can conduct The most forward biased diode will conduct – this will depend on the instantaneous phase voltage since the lower diodes have a common anode At any one time, only ONE of the upper diodes can conduct The most forward biased diode will conduct – this will depend on the instantaneous phase voltage since the upper diodes have a common cathode Uncontrolled (diode)

5. Three-phase Rectifiers The load voltage, v o, is the difference between the phase voltage (line-line voltage) For example, when D1 and D6 conduct, using KVL -v an +v O +v bn = 0 ==> v O = v an – v bn = v ab Uncontrolled (diode)

6. Three-phase Rectifiers The load voltage, v o, is the difference between the phase voltage (line-line voltage) When D1 and D2 conduct, using KVL -v an +v O +v cn = 0 ==> v O = v an – v cn = v ac Uncontrolled (diode)

7. Three-phase Rectifiers Uncontrolled (diode)

8. Three-phase Rectifiers Uncontrolled (diode)

9. Three-phase Rectifiers Controlled (SCR) The transition of output voltage to the maximum instantaneous line-line voltage can be delayed The reference of delay angle is when the SCR should conduct if it is a diode

10. Three-phase Rectifiers Controlled (SCR)

11. Three-phase Rectifiers Controlled (SCR) Delay angle beyond 90o is possible if the load is active (e.g. DC motor). The power is transferred from the load to the source.