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Two-quadrant converter T1 conducts  v a = V dc Q1Q2 VaVa IaIa T1 T2 D1 +Va-+Va- D2 iaia + V dc 

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Presentation on theme: "Two-quadrant converter T1 conducts  v a = V dc Q1Q2 VaVa IaIa T1 T2 D1 +Va-+Va- D2 iaia + V dc "— Presentation transcript:

1 Two-quadrant converter T1 conducts  v a = V dc Q1Q2 VaVa IaIa T1 T2 D1 +Va-+Va- D2 iaia + V dc 

2 Two-quadrant converter Q1Q2 VaVa IaIa T1 T2 D1 +Va-+Va- D2 iaia + V dc  D2 conducts  v a = 0 T1 conducts  v a = V dc Quadrant 1 The average voltage is made larger than the back emf

3 Two-quadrant converter Q1Q2 VaVa IaIa T1 T2 D1 +Va-+Va- D2 iaia + V dc  T2 conducts  v a = 0 Quadrant 2 The average voltage is made smaller than the back emf, thus forcing the current to flow in the reverse direction

4 Two-quadrant converter Q1Q2 VaVa IaIa T1 T2 D1 +Va-+Va- D2 iaia + V dc  D1 conducts  v a = V dc

5 5 Chopper fed DC drive Four-quadrant Chopper + V a  Q1 Q2 Q3 Q4 D1 D3 D4 D2 + V dc  Q1 & Q4 is ON Current Flow : V dc + _ Q 1 _Motor_Q 4 _V dc - Current I a & V a are positive Operates in First Quadrant Forward Motoring VaVa IaIa

6 6 Chopper fed DC drive Four-quadrant Chopper + V a  Q1 Q2 Q3 Q4 D1 D3 D4 D2 + V dc  Q1 is OFF & Q4 is ON. Inductor current has to flow in the same Direction. Diode D2 is FB Inductor Current freewheels through D 2 & Q4 Output Voltage is Zero

7 7 Chopper fed DC drive Four-quadrant Chopper + V a  Q1 Q2 Q3 Q4 D1 D3 D4 D2 + V dc  Q4 is OFF. Q2 is ON. Load is not connected with the source. Back Emf drives the current through Q2 & D4

8 8 Chopper fed DC drive Four-quadrant Chopper + V a  Q1 Q2 Q3 Q4 D1 D3 D4 D2 + V dc  Q2 is OFF. Diode D1 is FB Current flows through D4 & D1 Current Ia is negative & Va is positive. Operates in second quadrant. VaVa IaIa Forward Braking

9 9 Chopper fed DC drive Four-quadrant Chopper - V a + Q1 Q2 Q3 Q4 D1 D3 D4 D2 + V dc  Q3 & Q2 is ON Current Flow : V dc + _ Q 3 _Motor_Q 2 _V dc - Current I a & V a are negative Operates in third Quadrant

10 10 Chopper fed DC drive Four-quadrant Chopper - V a + Q1 Q2 Q3 Q4 D1 D3 D4 D2 + V dc  Q3 is OFF. Q2 is ON. Current has to be continuous. Diode D4 is FB Current flows through Q2,D4 & (Eb,La,Ra)

11 11 Chopper fed DC drive Four-quadrant Chopper - V a + Q1 Q2 Q3 Q4 D1 D3 D4 D2 + V dc  Q4 Is ON & Q2 is OFF. Back emf Drives the current through Q4 – D2 - MOTOR

12 12 Chopper fed DC drive Four-quadrant Chopper - V a + Q1 Q2 Q3 Q4 D1 D3 D4 D2 + V dc  Q4 IS Turned Off, D3 is FB Current Flows through Va + - D 3 – D 2 – Va - Va is negative. But current Ia is positive Operates in fourth quadrant

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