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18 Operation principle and hardware description
6-, 12- and 24-pulse supply units
￭
The supply units can be connected either to 6-pulse, 12-pulse or 24-pulse connection.
If 12-pulse or 24-pulse supply transformer is used, there can be a maximum of 4 diode
supply modules in one drive system. The figure illustrates the difference between
6-pulse and 12-pulse AC supply connections. The 6-pulse connection is standard.
The 12-pulse supply connection eliminates the fifth and seventh harmonics, which
remarkably reduces the harmonic distortion of the line current and the conducted
emissions. The 12-pulse connection requires a three-winding transformer, or two
separate transformers. There is a 30-degree phase shift between the two 6-pulse
supply lines.
1
1
Supply transformer
2
Switching equipment and fuses
3
Fuses for protecting input cabling
4
AC fuses for protecting supply unit against short circuit
5
Diode supply modules
6-pulse connection
3
1
2
12-pulse connection
2
3
5
4
5
4
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