Rockwell Automation SB3000 Configuration and Programming - Manual (Page 105)

SB3000 Pre-Charge Sequencing E-1
A
PPENDIX
E
SB3000 Pre-Charge Sequencing
The SB3000 Synchronous Rectifier System is shown in figure E.1 on the following
page.
The pre-charge is controlled via a pre-charge contactor, which is under the control of
the PMI Processor in the SB3000’s PMI rack. The contactor is mounted separately in
the power distribution cabinet. Any faults in contactor operation are reported in UDC
registers 202/1202 and 205/1205.
Pre-charge Sequencing During Normal Operation
When AC power is applied to the SB3000 Rectifier, back diodes in the IGBT power
devices will allow the capacitor bank to begin charging immediately through the fused
pre-charge resistors and line filter reactor.
Close Threshold
When control power is first turned on, the pre-charge contactor will be open. This will
allow the DC bus voltage to increase to near the peak of the AC line. The closing and
opening of the pre-charge contactor is a function of the measured DC bus voltage.
The close threshold is the peak of the configured AC line voltage minus 10 percent.
This threshold allows the rectifier to turn off with the AC line up to 10% low. The
contactor will stay open until the measured DC bus voltage reaches this threshold.
When the contactor closes, the PMI Processor will indicate this by turning on register
201/1201, bit 12 (CHG_FB@).
Close Threshold = Peak AC line voltage - 10%
Open Threshold
The open threshold is the peak of the configured AC line voltage minus 100 volts. The
contactor will open again if the measured DC bus voltage becomes less than this
level. If this occurs, register 201/1201, bit 12 will be turned off. The contactor will
remain open until bus voltage again reaches a steady state above the close threshold.
Open Threshold = Peak AC line voltage - 100V