Faculty of Engineering & Applied Science (FEAS)
Department of Electrical and Electronic Engineering
Program: B.Sc. in EEE
Course Code: EEE 378 Name of Course: Power Electronics Laboratory
Experiment No. 02: THREE PHASE HALF & FULL-WAVE RECTIFIER
Objectives of this experiment are to:
1. Understand and learn how diode characteristics are used to rectify three phase AC voltage to DC
voltage.
2. Learn the advantages of full wave rectifiers over half-wave rectifiers.
3. Learn the disadvantages of uncontrolled rectifiers.
Course Outcomes (COs), Program Outcomes (POs) and Assessment:
Domain / level
Expt Delivery methods
CO Statement Corresponding PO of learning Assessment tools
No. and activities
taxonomy
Lab tests
Simulation
CO1: Implement Investigation
Lab reports
different designed (PO4) Experiment
converters such as Modern Tool Affective Final lab test
01 domain/ Practice lab
AC-DC, DC-DC, Usage: (PO5)
analyzing level Open ended lab
AC-AC, DC-AC etc. Group
discussion Project show
& project
Tutorial
presentation
Lab tests
Simulation
CO2: Design
Lab reports
different converter Investigation Experiment
circuits using PSIM (PO4) Affective Final lab test
02 Modern Tool domain/analyzi Practice lab
software.
Usage: (PO5) ng level Open ended lab
Group
discussion Project show
& project
Tutorial
presentation
Required Equipments:
1. ED-2040-B (THREE PHASE HALF/FULL WAVE RECTIFIER)
2. Signal Generator
3. Oscilloscope
4. Load connection cord
5. Power supply connection cord
Theory:
A three phase half-wave rectifier is shown in Figure 2-1. In case of using load resistance (R), the
output waveform can be shown as in Figure 2-2. Like the figure, through the center tab, each a, b, c
phase is single phase half-wave rectification circuit, so a three phase half-wave rectification circuit
can be considered as consisting of three single phase half-wave rectification circuits. Whichever of
diode D1, D2 and D3 has the biggest voltage across it will conduct.
Figure 2-1: Three Phase Half Wave Rectifier
The load voltage Vab is given by the equation:
5π
6
6
V ab= ∫ √2 V sinθ dθ=1.17 V
4π π
6
Where V is phase voltage.
Figure 2-2: Output Waveforms of 3 phase Half Wave Rectifier
Figure 2-3 is bridged circuit of three phase full-wave rectifier. lf you make a circuit like Figure 2-3, it
basically acts like 2 three phase half-wave rectification circuits. D1 and D4, D3 and D6, D5 and D2
will not conduct at the same time.
Fig 2-3: Full Wave 3 Phase Bridge Rectifier
The output average load voltage can be calculated in the following manner:
V AC = √ 2 Vsinθ dθ
2π
V BC =√2 Vsin (θ− )dθ
3
π
2
1 2π
V ab= ∫ √ 2V sinθ−√ 2Vsin (θ− )dθ=1.35 V
2/6 π π 3
6
The diodes which will conduct at different times are indicated in Figure 2-4.
Fig 2-4: The output waveform of three phase full-wave rectifier
Working Procedure:
1. Measurement of input voltage: Connect the circuit as shown and record input voltage.
Figure 2-5: Measurement of input voltage of (a) Half wave rectifier. (b) Full wave rectifier
2. Measurement with R Load: Apply the power and then connect the probe of oscilloscope as
shown below.
Figure 2-6: (a) Half wave rectifier and (b) Full wave rectifier with R Load
3. Measurement with R-L Load: Connect the circuits as shown in Figure 2-7. Observe and
measure the output.
Figure 2-7: (a) Half wave rectifier and (b) Full wave rectifier with R-L load
4. Measurement with R-C Load: Connect the circuits as shown in Figure 2-8 and record the
waveform.
Figure 2-8: (a) Half wave rectifier and (b) Full wave rectifier with R-C load
Measured Results:
Observe, measure and record the waveform of the input voltage and the output voltage from steps 1-4
in working procedure. Plot them neatly in your graph paper.
Home Works:
1. Explain why the output wave shapes are different from each other in the steps above.
2. Explain in which cases three phase rectifiers are preferred over single phase rectifiers.
3. Explain what benefits would there be in using controlled three phase rectifiers?
