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Part 1 - Three-phase Diode Bridge Rectifier - Resistive Load
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Exercise 1: Varying Resistive Load (without smoothing capacitor C=0)
Open Three-Phase Diode Bridge Rectifier panel, choose in menu Pre-Selected: Three Phase: Varying Resistive Load without smoothing capacitor.
Figure 16: Three-Phase Diode Bridge Rectifier Panel with a Resistive Load of 16.5 ohms
Default Parameters
- AC Source Voltage : Ve= 120 V
- Frequency: 60 Hz
- R= 16.5 Ω
- For R = 16.5 ohms and Ve=120, measure the following values:
- the maximum peak value of the output voltage
- the minimum peak value of the output voltage
- the average output voltage
- Compare these values with the calculated ones
- Set Ve to 120V and the frequency to 60 Hz, and complete the following table for many values of R
R (Ω) | 16.5 | 25 | 50 | 100 |
|---|---|---|---|---|
Measured maximum peak value of the output current (A) | ||||
Calculated maximum peak value of the output current (A) | ||||
Measured minimum peak value of the output current (A) | ||||
Calculated minimum peak value of the output current (A) | ||||
Measured average output current (A) | ||||
Calculated average output current (A) | ||||
THD of AC-source current (%) |
Table 10: Impact of Varying Resistive Load
- Justify the shape of the output voltage and output current.
- What is the effect of increasing the resistance value on THD?
- Deduce the role of the three-phase diode bridge rectifier and compare it with the single-phase diode bridge rectifier.
Exercise 2 - Varying Resistive Load (with smoothing capacitor)
In the panel, choose under Pre-Selected: Three Phase: Varying Resistive Load with smoothing capacitor.
Figure 17: Three-Phase Diode Bridge Rectifier Panel with R=16.5 ohms and C= 470 µF
Default Parameters
- AC Source Voltage : Ve= 120 V
- Frequency: 60 Hz
- R= 16.5 Ω
- C= 470 µF
Complete Tables 11, 12 and 13 for different values of the smoothing capacitor.
Case 1: C= 470 µF
R (Ω) | 16.5 | 25 | 50 | 100 | 200 |
|---|---|---|---|---|---|
The maximum peak value of output voltage (V) | |||||
The minimum peak value of output voltage (V) | |||||
Form factor | |||||
Ripple factor | |||||
THD of AC-source Current (%) |
Table 11: Case 1- Effect of varying Resistive Load With Smoothing Capacitor
Case 2 : C= 1100 µF
R (Ω) | 16.5 | 25 | 50 | 100 | 200 |
|---|---|---|---|---|---|
The maximum peak value of output voltage (V) | |||||
The minimum peak value of output voltage (V) | |||||
Form factor | |||||
Ripple factor | |||||
THD of AC-source Current (%) |
Table 12: Case 2- Effect of varying Resistive Load With Smoothing Capacitor
Case 3 : C= 0.1 F
R (Ω) | 16.5 | 25 | 50 | 100 | 200 |
|---|---|---|---|---|---|
The maximum peak value of output voltage (V) | |||||
The minimum peak value of output voltage (V) | |||||
Form factor | |||||
Ripple factor | |||||
THD of AC-source Current (%) |
Table 13: Case 3- Effect of varying Resistive Load With Smoothing Capacitor
Now, set R to 25 Ω.
- Compare values of the peak-to-peak output voltages (without and with smoothing capacitor).
- How does the ripple factor change with and without the smoothing capacitor?
- What’s the relation between the peak-to-peak output voltage and the resistance (when C is constant)?
- For which capacitor value is the filtering considered more effective?
- What is the effect of increasing the capacitor filtering on the total harmonic distortion (THD) of the AC-source current?
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