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Homework 6 Harmonic Distortion Analysis

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Engineering
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Question 1
VFD
Rating- 480V, 150HP
Transformer
Rating- 750KVA, 5.75%Z
Effective % impedance of transformer in respect to the Drive?
Solution
First, we need to find the size of the load.
We convert 150HP into KVA
1HP = 746W
kVA=


. Horse power = 150HP
Therefore KVA =


111.9KVA
Effective %Z =


 
Where the transformer load is 750KVA, Transformer intendance is 5.75% and VFD is 111.9KVA


  
The effective % impedance of transformer in respect to the Drive is therefore, 0.9192%
Question 2
Transformer
Effective %Z 1%
Impendence line reactor
%Z = 5%
The %THD-i expected when the %Z is 1% is 71.80% according to the Harmonic current Distortion Table-
6 pulse rectifiers.
Question 3
6 pulse non-linear Load
%Z = 6.5%
What is %THD-i?

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The total harmonic Distortion (%THD-i) is 31.47% according to the Harmonic current Distortion Table-6
pulse rectifiers
Question 4
6- pulse drive
%Z 5%
Percentage operation- 60% load
The percentage operation can be written as 0.6
Effective %Z
Eff % =    
The effective % impedance = 3%
%THD-i
The anticipated %THD-i according to the table is 43.82%. (Harmonic current Distortion Table-6 pulse
rectifiers)
Question 5
% impedance is 4.75%
Estimated current spectrum for the first six harmonics
Harmonics
I1
I5
I7
I11
I17
I19
% of
fundamental
100
33.32
13.28
6.07
2.35
1.84
Calculation
590
590*33.32%
590*13.28%
590*6.07%
590*2.35%
590*1.84%
Current
Spectrum
590
196.59
78.352
35.813
072
10.856
% of fundamentals are from the table
Question 6
Harmonic triangle for a load with 40% THD-i

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Question 1 VFD Rating- 480V, 150HP Transformer Rating- 750KVA, 5.75%Z Effective % impedance of transformer in respect to the Drive? Solution First, we need to find the size of the load. We convert 150HP into KVA 1HP = 746W kVA= 𝐻𝑜𝑟𝑠𝑒 𝑃𝑜𝑤𝑒𝑟 ∗746𝑊 1000 Therefore KVA = Effective %Z = . Horse power = 150HP 150∗746 1000 = 111.9KVA 𝑉𝐹𝐷 𝑇𝑟𝑎𝑛𝑠𝑓𝑜𝑟𝑚𝑒𝑟 𝐿 ∗ 𝑡𝑟𝑎𝑛𝑠𝑓𝑜𝑟𝑚𝑒𝑟 %𝑍 Where the transformer load is 750KVA, Transformer intendance is 5.75% and VFD is 111.9KVA 111.9 ∗ 5.75% = 0.9192% 750 The effective % impedance of transformer in respect to the Drive is therefore, 0.9192% Question 2 Transformer Effective %Z – 1% Impendence line reactor %Z = 5% The %THD-i expected when the %Z is 1% is 71.80% according to the Harmonic current Distortion Table6 pulse rectifiers. Question ...
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