Power Electronics - AC to DC Converters Complete Study Notes

Single-phase half wave diode rectifier

In single-phase half-wave rectifier, for one cycle of supply voltage, there is one half cycle of output, or load voltage. That’s why; it is called as single-phase one pulse rectifier.

Single Phase Half Wave Diode Rectifier with R Load:

Figure : Single Phase Half Wave diode rectifier with R Load

During the positive half cycle, diode is forward biased, so it conducts from ωt = 0 to ωt = π. During the positive half cycle, output voltage V₀ = V_s and load current  At ωt = π, V₀ = 0 and for R load, i₀ is also zero. After ωt = π, diode D is reverse biased, it is therefore turned-off and goes into blocking sate. Hence, output voltage and current becomes zero from ωt = π to ωt =2π. After ωt = 2π, diode is again forward biased, conduction begins and the cycle repeats. For resistive load, output current i₀ has the same waveform as that of the output V₀.

Figure : Waveforms of Single-Phase Half Wave diode rectifier with R Load

Single-Phase Half wave Diode Rectifier with L Load:

Figure : Single Phase Half Wave diode rectifier with L Load

Figure : Waveforms of Single-Phase half wave diode rectifier with L Load

Single -phase full wave diode rectifier

There are two types of full wave diode rectifiers:

• Single-phase full wave mid-point (centre-tapped) diode rectifier
• Single-phase full wave diode bridge rectifier

 Single-Phase Full wave Mid-point Diode Rectifier:

Figure : Single Phase full wave mid-point diode rectifier

Figure : Waveforms for Single Phase full wave mid-point diode rectifier

Single-Phase Full wave Diode Bridge Rectifier:

Figure : Single Phase full wave diode Bridge rectifier

Figure : Waveforms for Single Phase full wave diode Bridge rectifier

Single phase half wave-controlled rectifier with R Load

The simplest form of phase-controlled rectifier consists of a thyristor feeding power to a R load. Let thyristor T be triggered at firing angle  in each positive half cycle. The corresponding waveforms are shown in figure below.

Figure: Single-Phase half wave-controlled rectifier with R Load

Figure: Waveforms for Single-Phase half wave-controlled rectifier with R Load

  Single phase half wave-controlled rectifier with RL load:

Figure: Single Phase half wave-controlled rectifier with RL Load

Figure: Waveforms for Single Phase half wave-controlled rectifier with RL Load

Three Phase Half Wave Diode Rectifier:

Three-Phase Mid-point 6-Pulse Diode Rectifier:

Three-phase diode bridge rectifier:

Three-phase half wave controlled rectifier:

Figure : Three Phase half wave rectifier with R Load

If V_mp is the peak value of phase voltage, the average value of the output voltage,

If the input supply frequency is f, then output has a ripple frequency of 3f. Hence the convertor is also called 3-pulse converter.

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