Page 124 - Uninterruptible Power Supplies

Harmonic Distortion of the Supply
122 Chapter Four

Figure 4.2 Circuit diagram, operating sequence, and idealized currents of a three-phase
bridge rectifier.

It follows that a three-phase bridge will take harmonic currents of
the orders 5 and 7, 11 and 13, 17 and 19, etc. and if the pulse number
is increased to 12 by adding a second bridge with a phase displacement
of 30°, harmonic currents of the orders 5 and 7, 17 and 19, etc., will be
suppressed leaving only the orders 11 and 13, 23 and 25, etc. The
Fourier analysis indicates that the magnitudes of these harmonic cur-
rents are similarly based on a simple mathematical relationship.

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