4. Rectifier.pptx

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1. RECTIFIER

2. What is Rectifier? A  rectifier  is an electrical device that converts alternating current(AC) to direct current(DC). This process is known as rectification . Its also called Converters . AC Voltage Pulsated DC Voltage Rectifier

3. Diode Based Rectifiers Half Wave Rectifier Full Wave Rectifier Bridge Type Centre Tap Transformer Type

4. Types of Rectifier

5. Half Wave Rectifier (HWR) Half-wave rectifiers are used to c onvert AC voltage to DC voltage, and it required a single diode  to construct the circuit. The diode only conducts when the anode is positive with respect to cathode, the current will flows only during the positive half cycle of the input voltage i.e., current flow in one direction.

6. Half Wave Rectifier (HWR) D R L v(t) = V m sin ω t v o (t) D=ON D=OFF D=ON

7. Working of half wave rectifier AC voltage is applied to the primary winding of the step-down transformer which step-down to low voltage at the secondary winding which will be applied to the diode. During the positive half cycle of the AC voltage, the diode will be forward biased and the current flows through the diode . During the negative half cycle of the AC voltage, the diode will be reverse biased and the flow of current will be blocked .

8. v(t) time 5 10 15 20 + - Working of HWR At time t=0 sec Phase Potential = 0 Volts Neutral Potential =0 Volts A K 0V 0V V A =V K Diode Reverse Bias. Diode act as an OFF switch D R L 230V,50Hz AC Supply A K P N NO OUTPUT VOLTAGE vo (t) D R L 230V,50Hz AC Supply A K P N

9. v(t) time 5 10 15 20 +325V - Working of HWR At time t=5 msec Phase Potential = 325Volts Neutral Potential =0 Volts A K 325V 0V V A > V K Diode is forward biased Diode act as an ON switch D R L 230V,50Hz AC Supply A K P N OUTPUT VOLTAGE IS PRESENT vo (t) D R L 230V,50Hz AC Supply A K P N

10. v(t) time 5 10 15 20 + - Working of HWR At time t=10 msec Phase Potential = 0 Volts Neutral Potential =0 Volts A K 0V 0V V A =V K Diode Reverse Bias. Diode act as an OFF switch D R L 230V,50Hz AC Supply A K P N NO OUTPUT VOLTAGE vo (t) D R L 230V,50Hz AC Supply A K P N

11. v(t) time 5 10 15 20 + - Working of HWR At time t=15 msec Phase Potential = -325 Volts Neutral Potential =0 Volts A K -325 V 0V V A <V K Diode Reverse Bias. Diode act as an OFF switch D R L 230V,50Hz AC Supply A K P N NO OUTPUT VOLTAGE vo (t) D R L 230V,50Hz AC Supply A K P N

12. Graphical representation V in  Input Voltage (Sinusoidal Waveform) V out  Output Voltage (rectified output half wave)

13. HWR OUTPUT WAVEFORMS 180 360 540 720 180 360 540 720 D-ON D-ON D-ON D-OFF D-OFF

14. Half Wave Rectifier With Filter vo (t) D R L 230V,50Hz AC Supply A K P N C V avg time

15. Half wave rectifier Advantage: Simple in circuit construction. Cost efficient. Disadvantage: Filters are required to get pure DC. AC supply delivers power during half cycle only. So output is low. Ripple factor is quite high (RF=1.21) than full wave rectifier Efficiency is 40.6% only.

16. Full wave rectifier A  Full Wave Rectifier  is a circuit, which converts an ac voltage into a pulsating dc voltage using both half cycles of the applied ac voltage. It uses two diodes of which one conducts during one half cycle while the other conducts during the other half cycle of the applied ac voltage.

17. Full wave rectifier Classification full wave rectifiers into, Centre-tapped Full Wave Rectifier Full Wave Bridge Rectifier

18. Full wave rectifier with center-tapped transformer Centre-tapped Transformer: It is a normal transformer with slight modification. It has an addition wire connected to the exact centre of the secondary winding. This type of construction divides the AC voltage into two equal and opposite voltages namely + Ve voltage ( V a ) and - Ve voltage ( V b ). The total output voltage is,

19. Full wave rectifier with center-tapped transformer

20. FULL WAVE RECTIFIER A  full wave rectifier  is defined as a type of  rectifier  that converts both halves of each cycle of an alternating  wave  (AC signal) into a pulsating DC signal

21. FULL WAVE RECTIFIER Center tap Transformer Based FWR What is Centre Tap Transformer? N2/2 N2/2 N2 TURNS N1 TURNS N1 TURNS

22. Center tap Transformer 100 Volts 100 Volts 1:1 50 Volts 50 Volts 100 Volts 1 : 0.5 : 0.5

23. Behavior of Center tap Transformer with AC Supply 1 : 0.5 : 0.5 V m Vm / 2 - Vm / 2 - V m

24. Behavior of Center tap Transformer with AC Supply 1 : 0.5 : 0.5 + + - - + + - - 0 V

25. FULL WAVE RECTIFIER 1 : 0.5 : 0.5 P N 0V D1 D2 R L A A K K v o (t)

26. FULL WAVE RECTIFIER When applying an AC voltage to the input transformer. During the positive half-cycle of the AC voltage, terminal 1 will be positive , centre-tap will be at zero potential and terminal 2 will be negative potential. This will lead to forward bias in diode D 1 and cause current to flow through it. (i.e., D 1 Conducts) During this time, diode D 2 is in reverse bias and will block current through it.

27. During Positive Half Cycle D1-ON & D2-OFF D2-OFF 1 : 0.5 : 0.5 P N 0V D1-ON R L + - A K K A Note the Current Direction

28. During the negative half-cycle of the input AC voltage, terminal 2 will become positive with relative to terminal 2 and centre-tap. This will lead to forward bias in diode D 2 and cause current to flow through it. (i.e., D 2 Conducts) During this time, diode D 1 is in reverse bias and will block current through it.

29. During Negative Half Cycle D1-OFF & D2-ON D2-ON 1 : 0.5 : 0.5 P N 0V D1-OFF R L + - A K K A Note the Current Direction

30. Waveforms D1-ON D1-ON D2-ON D2-ON DC OUTPUT VOLTAGE INPUT AC VOLTAGE Vm / 2 Vm / 2 Vm / 2 Vm / 2 V m - V m

31. FWR with Filter 1 : 0.5 : 0.5 P N 0V D1 D2 R L A A K K v o (t)

32. FWR Output with Filter V m / 2

33. Full Wave Bridge Rectifier Diodes namely A, B, C and D which form a bridge circuit as shown.

34. BRIDGE RECTIFIER R L v s D1 D2 D3 D4 P N

35. BRIDGE RECTIFIER – WORKING During Positive Half Cycle R L v s D1 D2 D3 D4 P N + 0V + : high potential D1,D3 – ON D2,D4 – OFF v o (t) V m V m LOOK AT THE CURRENT DIRECTION A K

36. BRIDGE RECTIFIER – WORKING During Negative Half Cycle R L v s D1 D2 D3 D4 P N - 0V + : high potential D1,D3 – OFF D2,D4 – ON v o (t) V m V m LOOK AT THE CURRENT DIRECTION A K

37. Full wave rectifier Advantages: Efficiency is higher ( ɳ =81.2%)  Low power loss because no voltage signal is wasted in the rectification process. Produces large DC power output Ripple factor is less. Disadvantages: The centre-tapped rectifier is more expensive than half-wave rectifier and tends to occupy a lot of space. Peak Inverse Voltage(PIV) rating of diode is higher.

38. Application of rectifier Battery Charger DC Power Supply DC welder DC Motor Drive

39. Comparison of Rectifiers