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Assessment Cover Sheet
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Assessment Title
Active Power Factor Correction Project
Program Title:
Bachelor of Engineering Technology
Course No.:
ENB6008
Course Title:
Power Electronics
Student Name:
Ali Alsharakhat
Student ID:
201201211
Tutor:
John Leek
Due Date: 8/1/2015
Date submitted: 8/1/2015
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Table of Contents
Abstract ................................................................................................................................................4
Objectives .............................................................................................................................................4
Part 1 ....................................................................................................................................................5
Experimental method .......................................................................................................................5
Test results without smoothing capacitor ........................................................................................5
Test results with 10,000uF smoothing capacitor .............................................................................7
Theory ...............................................................................................................................................8
Problem with low power factor........................................................................................................9
Part 2 ..................................................................................................................................................10
DCM and CCM.................................................................................................................................10
2
Table of Figures
Figure 1: Part 1 circuit diagram ............................................................................................................5
Figure 2: Circuit designed by using altium ...........................................................................................6
Figure 3: Simulation results ..................................................................................................................7
Figure 4: Power triangle .......................................................................................................................8
Figure 5: Change in phase with change in load ....................................................................................8
Figure 6: Efficiency against output power plot ..................................................................................12
Figure 7: Output voltage against output power plot .........................................................................12
Table of Tables
Table 1: Input measurements ..............................................................................................................5
Table 2: Output measurements ...........................................................................................................5
Table 3: Input measurements with smoothing capacitor ....................................................................7
Table 4: Output measurements with smoothing capacitor .................................................................7
Table 5: Ripple measurements with smoothing capacitor ..................................................................7
Table 6: Input measurements ............................................................................................................11
Table 7: Output measurements .........................................................................................................11
3
Abstract
The aim of this project was to correct the power factor caused by a power supply. Correcting the
power factor reduces the current harmonics and decreases the reactive power, which is crucial in
an industrial field. The active PFC circuit was designed by calculations according to the datasheet of
a power factor controller (TDA4862), built and then tested by using a power meter that records the
PF. Results obtained were discussed and plotted.
Objectives
4
Part 1
This part will investigate the change in power factor when the output from a bridge rectifier is
connected to a capacitor. It will also investigate the change in power factor when the resistor value
at the output is changed.
Experimental method
Figure 1: Part 1 circuit diagram
On the first test, a full-wave rectifier was connected to a 24V AC power supply, and the output was
connected to a 10Ω or 25Ω resistor. According to theory, the power factor on this circuit design
would be unity because it is purely resistive.
On the second test, a 10,000uF capacitor was added to the output of the circuit. In theory, there
would be a leading power factor (current leading the voltage).
Test results without smoothing capacitor
Input measurements
Table 1: Input measurements
Input voltage
Input current
Input real
ac Secondary
ac Secondary
power
10Ω
24.7V
2.26A
25Ω
25.4V
0.959A
Load Resistor
Input VA
Power factor
55.6W
55.8
1
24.3W
25.4
1
Output measurements
Table 2: Output measurements
Peak input
Average DC
Output voltage
voltage
voltage
ripple
10Ω
32.22V
20.5V
10.45V
51.9W
25Ω
33.3V
21.2V
10.8V
20.5W
Load Resistor
Power lost at 10Ω: 𝑃𝑙𝑜𝑠𝑠 = (24.7 ∗ 2.26) − 51.9 = 3.9𝑊
5
Output Power
Reactive power at 10Ω:𝑃𝑟𝑒𝑎𝑐𝑡𝑖𝑣𝑒 = √55.82 − 55.62 = 4.7𝑉𝐴𝑟
Power lost at 25Ω: 𝑃𝑙𝑜𝑠𝑠 = (25.4 ∗ 0.959) − 20.5 = 3.86𝑊
Reactive power at 25Ω:𝑃𝑟𝑒𝑎𝑐𝑡𝑖𝑣𝑒 = √25.42 − 24.32 = 7.4𝑉𝐴𝑟
As this is a resistive load, the results agree with the theory because the reactive power is negligible
(PF is unity)
Figure 2: Circuit designed by using altium
6
Figure 3: Simulation results
Test results with 10,000uF smoothing capacitor
Input measurements
Table 3: Input measurements with smoothing capacitor
Input voltage
Input current
Input real
ac Secondary
ac Secondary
power
10Ω
23.7V
4.56A
25Ω
24.6V
2.21A
Load Resistor
Input VA
Power factor
82.6W
107.9
0.76
38.6W
54.2
0.71
Output measurements
Table 4: Output measurements with smoothing capacitor
Peak input
Average DC
Output voltage
voltage
voltage
ripple
10Ω
28.55V
27.45V
1.7V
75.35W
25Ω
31.53V
30.7V
2.97V
37.7W
Load Resistor
Output Power
Ripple voltage measurements
Table 5: Ripple measurements with smoothing capacitor
Load Resistor
7
Load Current
Ripple voltage pk-pk
RMS ripple voltage
10Ω
2.745A
5.49V
3.88V
25Ω
3.07A
6.14V
4.34V
Peak current at 10Ω = 8.86A
Peak current at 25Ω = 4.7A
Frequency of ripple current = 100Hz
Theory
Power factor is the cosine of the phase angle between the voltage and current, which is the ratio of
the real power to apparent power. The apparent power is the total supplied power and the real
power is the power that produces the real work. The reactive power (lost power) is the power
required to produce a magnetic field.
Figure 4: Power triangle
The reactive power causes the phase shift between current and voltage, which is caused by an
inductive or a capacitive load in the circuit. An inductor causes the current to lag the voltage (lagging
power factor) and a capacitor causes the current to lead the voltage (leading power factor).
Figure 5: Change in phase with change in load
8
Problem with low power factor
When the power factor is low, the reactive power would be high and leads to an increase in the
required apparent power to make up for the loss. Increasing the power factor would decrease the
required input power, which in turn leads to a greater efficiency.
Uncorrected power factor causes power losses in a system. As power losses increase, voltage drops
and harmonics occur. Excessive voltage drops and harmonics can cause overheating and premature
failure of equipment.
9
Part 2
Introduction - DCM and CCM
When current through an inductor falls to zero, the condition is Discontinuous Conduction Mode
(DCM). When the inductor current never falls to zero, or when the rectification is synchronized, the
condition is Continuous Conduction Mode (CCM).
With synchronized rectification, active switches are used for rectifiers. Therefore, unless the switch
turns off, the conduction mode will always be continuous. The method used in the project is DCM
Advantages of CCM over DCM

In DCM, the current must fall to zero before the start of the next cycle, hence low
inductance values must be used. Low inductance values results in higher RMS and peak
inductor currents.

The DCM method causes ringing and leads to an undesirable noise at the output.
Design and calculation
Rsense
Minimum input voltage = 𝑉𝑖𝑛𝑚𝑖𝑛 = 24 − 1 = 23𝑉
Minimum peak input voltage = 𝑉𝑖𝑛𝑝𝑘𝑚𝑖𝑛 = √2 ∗ 23 = 32.53𝑉
Minimum efficiency = 𝜂 = 0.9
Pout = 50W
2∗𝑃𝑜𝑢𝑡
2∗50
Max peak input current = 𝐼𝑖𝑛𝑝𝑘𝑚𝑎𝑥 = 𝑉𝑖𝑛𝑝𝑘𝑚𝑖𝑛∗𝜂 = 32.53∗0.9 = 3.42𝐴
Max high frequency peak current = 2 ∗ 𝐼𝑖𝑛𝑝𝑘𝑚𝑎𝑥 = 2 ∗ 3.42 = 6.84𝐴
Max current sense threshold = 𝑉𝑖𝑠𝑒𝑛𝑠𝑒𝑚𝑎𝑥 = 1.3𝑉
𝑀𝑎𝑥 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑠𝑒𝑛𝑠𝑒 𝑡ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑
Rsense = 𝑀𝑎𝑥 ℎ𝑖𝑔ℎ 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 𝑝𝑒𝑎𝑘 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 = 0.19Ω
Inductor
The primary winding should have 0.1mH
Steps taken to reach 0.1mH:
L (at start) = 0.202mH
n (turns removed) = 2
∆L = 0.202-0.1912 = 0.0108mH
∆𝐿 2𝑛 0.0108 ∗ 10−3 2 ∗ 2
=
=
𝐿
𝑁
0.202 ∗ 10−3
𝑁
N (number of turns) = 75
10
𝑁 = 75
Table 6: Input measurements
Load
Input voltage Input current
Input power
Apparent
Reactive
resistance (Ω)
(V)
(A)
(W)
power (VA)
power (VAR)
33
22.8
2.57
56.9
58.5
13.4
37
23
2.35
53.1
54
9.8
44
23.2
2.05
47
47.7
8.1
54
23.5
1.59
37.2
37.3
3
65
23.9
1.28
30.6
30.6
1.3
87
24.4
0.93
22.7
22.7
0
100
24.2
0.82
19.9
19.9
0
Table 7: Output measurements
Load resistance
Output voltage
Output power
(Ω)
(V)
(W)
33
40.4
49.5
0.97
2.63
86.9
37
40.5
44.3
0.98
2.34
83.5
44
41.7
39.4
0.99
2.05
83.9
54
41.7
32.1
1
1.72
86.4
65
41.7
26.7
1
1.59
87.3
87
41.7
19.9
1
1.3
87.9
100
41.7
17.4
1
1.17
87.2
11
PF
Ripple Vrms
(V)
Efficiency (%)
Efficiency against Output Power plot
90
80
70
Efficiency (%)
60
50
40
30
20
10
0
15
20
35
30
Output Power (Watts)
25
40
45
40
45
50
Figure 6: Efficiency against output power plot
Output Voltage against Output Power plot
45
40
Output Voltage (V)
35
30
25
20
15
10
5
0
15
20
25
Figure 7: Output voltage against output power plot
12
30
35
Output Power (Watts)
50
13