Rockwell Automation 2364F Regenerative DC Bus Supply Unit (RGU) - Manual (Page 25)

Publication 2364F-5.01– October 2003
Overview 1-9
Diode Bridge Operation (RGU Not Enabled)
When the RGU is not enabled, the IGBTs are not modulating. In this
mode, current flows only through the free-wheeling diodes. These
diodes permit current flow in one direction, from anode to cathode.
When an AC voltage is applied to a diode, the output of that diode is a
pulsating DC voltage. This mode is identical to a 3-phase diode
bridge with line reactors.
Operating as a 3-phase diode bridge, the RGU provides an average
DC bus voltage that is approximately 1.35 times the rms line-to-line
voltage. At full load, this average DC bus voltage will decrease to
about 1.24 times the rms line-to-line voltage, due to the line reactors.
Refer to Figure 1.5 for an illustration of the 3-phase AC input voltage
and current waveforms when the RGU is not enabled.
Figure 1.5
3-Phase AC Line Voltage To Neutral and AC Line Current of a Diode Bridge
(RGU Not Enabled)
V
line
I
line