12/18/2022
Total Harmonic Distortion (THD)
THDF (for "fundamental"), and THDR (for "root mean square")
are related as shown above.
Some use the term “Distortion Factor" as a synonym for
THDR, while others use it as a synonym for THDF.
The International Electrotechnical Commission (IEC) also
defines another term total harmonic factor for the "ratio of the
RMS value of the harmonic content of an alternating quantity
to the RMS value of the quantity" using a different equation.
Also there is IEEE standard for THD.
1
THD(V) Value
Comments
THD(V) < 5%
Insignificant distortion of the voltage wave: little risk of disturbance.
5% < THD(V) < 8%
Significant distortion of the voltage wave: risk of heat rise and disturbance.
8% < THD(V)
Significant distortion of the voltage wave: there is a high risk of disturbance unless the installation is calculated
and sized based on this distortion.
THD(I) Value
Comments
THD(I) < 10%
Low harmonic currents: little risk of disturbance.
10% < THD(I) < 50%
Significant harmonic currents: risk of heat rise, oversizing of supplies.
50% < THD(I)
High harmonic currents: the risks of disturbance, degradation, and heat rise are almost certain unless the
installation is calculated and sized with this restriction in mind.
2
1
12/18/2022
10.4 Three-phase Full
Converters
3
4
2
12/18/2022
5
6
3
12/18/2022
7
8
4
12/18/2022
10.5 Three-phase dual
Converters
9
10.5 three-phase dual Converters
10
5
12/18/2022
10.5 three-phase dual Converters
11
10.5 three-phase dual Converters
12
6
12/18/2022
13
10.6 Pulse-WidthModulation (PMW)
Control
14
7
12/18/2022
15
Single-phase Converter with PWM Control
16
8
12/18/2022
10.6.1 PWM Control
17
10.6.2 Single-phase Sinusoidal PWM
18
9
12/18/2022
10.6.3 Three-phase PWM Rectifier
19
20
10
12/18/2022
2 Forced-commutated Cascaded
Converters
21
10.7 Single-phase Series Converters
22
11
12/18/2022
10.7 Single-phase Series Converters
23
24
12
12/18/2022
Example 10.7 Finding the Input PF of a Series Single-phase Full Converter
25
26
13
12/18/2022
10.8 12-pulse Converters
27
28
14
12/18/2022
Thanks for
Today
29
End of
Controlled
Rectifiers
30
15