Single-Phase Diode Rectifier| Dr. Mithun Mondal

§ 01

Introduction

This experiment converts single-phase AC to DC using a full-wave bridge diode rectifier. The circuit is implemented in MATLAB Simulink and verified with a hardware prototype. Both resistive and RL loads are studied.

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Learning Objectives

Analyse Full-Wave Bridge Rectifier Performance

Determine RMS, average, form factor, and ripple factor for R and RL loads. Perform FFT harmonic analysis and compare simulation vs hardware measurements.

§ 02

Theory

A full-wave bridge rectifier uses four diodes (D1–D4). During the positive half-cycle, D1 and D2 conduct; during the negative half-cycle, D3 and D4 conduct. For a resistive load, the output current tracks the output voltage waveform.

Full-wave bridge rectifier circuit — Fig. 1 — Single-phase full-wave bridge diode rectifier with output waveform.

Full-Wave Rectifier Output Metrics

\[V_{dc} = \frac{2V_m}{\pi},\quad V_{rms} = \frac{V_m}{\sqrt{2}},\quad \text{FF} = \frac{\pi}{2\sqrt{2}} \approx 1.11,\quad \text{RF} = \sqrt{\text{FF}^2-1} \approx 0.482\]

For \(V_m = 50\text{ V}\): \(V_{dc} = 31.83\text{ V}\), \(V_{rms} = 35.35\text{ V}\). PIV of each diode = \(V_m = 50\text{ V}\).

RL Load Effect: Adding inductance smooths the current waveform. The output current becomes more continuous, reducing ripple. The diode conduction period may extend beyond the source voltage zero-crossing.

§ 03

Simulation — R Load (Problem 1)

Problem Statement

Implement the 1-phase uncontrolled full-wave rectifier with R = 25 Ω. Input: \(V_{peak} = 50\text{ V}\) (35.35 V RMS), 50 Hz. Attach waveforms and perform FFT analysis.

Simulink full-wave rectifier model — Fig. 2 — Simulink model of the single-phase full-wave bridge diode rectifier.

§ 04

Simulation — RL Load (Problem 2)

Problem Statement

Add L = 6 mH in series with R = 25 Ω. Observe changes in output voltage waveform and FFT analysis. Compare with pure R load results.

§ 05

Hardware — R Load

Hardware circuit for R load — Fig. 3 — Hardware wiring diagram: full-wave bridge rectifier with R load (25 Ω).

Connect circuit as in Fig. 3 (R = 25 Ω). Switch ON 3φ supply MCB.
Switch ON POWER MODULE MCB and SCR–Diode Power Module MCB.
Increase voltage slowly to 35.35 V RMS using + push button.
Connect CRO probes across R load. Observe output voltage waveforms and FFT in DSO.

§ 06

Hardware — RL Load

Hardware circuit for RL load — Fig. 4 — Hardware wiring diagram: full-wave bridge rectifier with RL load (25 Ω, 6 mH).

Connect circuit as in Fig. 4 (R = 25 Ω, L = 6 mH). Switch ON 3φ supply MCB.
Repeat the hardware procedure from the R-load section (steps 2–4).

§ 07

Results

Required waveforms to attach (Simulink & Hardware): Output Voltage, Output Current, Diode Voltage, Diode Current, Input Voltage, Input Current, FFT bar charts.

Performance Parameters — Simulation

Parameter	R Load	RL Load
V_RMS (V)
I_RMS (A)
V_AVG (V)
I_AVG (A)
Form Factor
Ripple Factor

Performance Parameters — Hardware

Parameter	R Load	RL Load
V_RMS (V)
V_AVG (V)
Form Factor
Ripple Factor

FFT Analysis

Parameter	R Load — Sim	R Load — HW	RL Load — Sim	RL Load — HW
THD (%)
V_fundamental (RMS)
V 2nd Harmonic (RMS)
V 3rd Harmonic (RMS)
I_THD (%)
I_fundamental (RMS)
I 2nd Harmonic (RMS)
I 3rd Harmonic (RMS)

In dB

\[20\log(V_{fundamental,rms}) = \underline{\hspace{4cm}}\text{ dB}\]