Page 340 - Power Electronics Handbook

330 D.C. link frequency changers

Table 13.18 Harmoafe content of a quare modulated bi-directional wave withfT/fs = 10
~~
~
Harmonic R. M.S. voltage as percentage of d.c. supply
number
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
~
1 8.94 17.9 26.9 35.9 44.9 53.9 62.9 71.9 81.0 90.0
2 0 0 0 0 0 0 0 0 0 0
3 2.81 5.67 8.60 11.6 14.6 17.6 20.7 23.8 26.9 30.0
4 0 0 0 0 0 0 0 0 0 0
5 1.47 3.04 4.70 6.44 8.26 10.1 12.1 14.0 16.0 18.0
6 0 0 9 0 0 0 0 0 0 0
7 0.80 1.74 2.82 4.01 5.32 6.71 8.18 9.71 11.3 12.9
8 0 0 0 0 0 0 0 0 0 0
9 0.32 0.84 1.54 2.40 3.42 4.57 5.83 7.18 8.57 10.0
10 88.9 85.6 80.2 72.8 63.7 52.9 40.9 27.8 14.1 0
11 0.10 0.05 0.44 1.05 1.8 2.90 4.08 5.38 6.76 8.18
12 0 0 0 0 0 0 0 0 0 0
13 0.57 0.83 0.77 0.39 0.30 1.26 2.46 3.84 5.35 6.92
14 0 0 0 0 0 0 0 0 0 0
15 1.23 2.07 2.46 2.38 1.84 0.86 0.49 2.15 4.02 6.00

Table 13.19 Harmonk content of a quare modulated bi-dlnetional wave withfr/fs = 20
Harmonic R. M.S. voltage as percentage of d.c. supply
number
0.1 0.2 0.3 0.4 . 0.5 0.6 0.7 0.8 0.9 1.0
1 8.99 18.0 27.0 36.0 45.0 54.0 63.0 72.0 81.0 90.0
2 0 0 0 0 0 0 0 0 0 0
3 2.95 5.92 8.90 11.9 14.9 17.9 20.9 24.0 27.0 30.0
4 0 0 0 0 0 0 0 0 0 0
5 1.72 3.47 5.23 7.M 8.83 10.6 12.5 14.3 16.2 18.0
6 0 0 0 0 0 0 0 0 0 0
7 1.17 2.38 3.62 4.89 6.18 7.49 8.82 10.2 11.5 12.9
8 0 0 0 0 0 0 0 0 0 0
9 0.85 1.75 2.69 3.66 4.67 5.71 6.76 7.83 8.91 10.0
10 0 0 0 0 0 0 0 0 0 0
11 0.63 1.32 2.06 2.85 3.68 4.54 5.43 6.33 7.25 8.18
12 0 0 0 0 0 0 0 0 0 0
13 0.47 1.00 1.60 2.25 2.96 3.70 4.48 5.28 6.10 6.92
14 0 0 0 0 0 0 0 0 0 0
15 0.33 0.75 1.23 1.78 2.39 3.05 3.75 4.48 5.24 6.00

unidirectional switching and is due to the absence of any ‘zero’ periods in
the waveform. For maximum modulation the output reduces to a square
wave and the harmonic content is identical to comparable quasi-square and
unidirectional systems.
With bi-directional switching the odd harmonic content generally
increases as the operating frequency is raised, whilst the reverse was true
for unidirectional switching. However, the presence of the large-valued
even harmonics still makes it desirable to operate this system at an inverter
frequency of the order of twenty times the desired output frequency.