Rockwell Automation SA3000 High Power Modules - Manual (Page 57)

SA3000 Internal DC Bus Control B-1
A
PPENDIX
B
SA3000 Internal DC Bus Control
Each DC input High Power SA3000 Power Module contains a capacitor bank which
must be charged before the Power Module can produce current. Because the
capacitor bank acts like a DC bus, i.e., it supplies DC power to the inverter section of
the Power Module, the capacitor bank is referred to as an “internal” DC bus.
An external DC bus, which can be used to supply DC voltage to the Power Module, is
provided by the user. This external DC bus is not under the control of the SA3000
drive.
The internal DC bus in each Power Module consists of the capacitor bank and
discharge/voltage sharing resistors. In addition, an optional pre-charge contactor and
resistor may be part of this system. Note that if an optional disconnect switch is used,
the pre-charge option must also be used. See figure B.1 for a simplified internal DC
bus schematic.
If the pre-charge option is present, DC input power can be turned on either before or
at the same time that bus control is enabled. Because the pre-charge contactor is
initially open, bus charging actually begins as soon as power is turned on to the Power
Module, regardless of whether or not bus control has been enabled by the
programmer. In the absence of explicit control by the programmer, current to the bus is
limited by the pre-charge resistors. Note that if the pre-charge option is not present,
the external bus is responsible for controlling the charging of the inverter’s internal DC
bus capacitors.
Figure B.1 – Internal DC Bus Schematic
Discharge
and
Voltage
Sharing
Resistors
(+)
(–)
Pre-charge
Contactor
Pre-charge
Resistor
(Optional)
Internal DC Bus
DC Bus
Capacitors
To B & C
Power Modules
(If Used)
347
345
External
DC Bus
47(+)
45(–)
Disconnect
Switch
(Optional)
FPMA
Power
Devices
AC
Motor