Rockwell Automation SB3000 AC Power Modules - Manual (Page 73)

Theory of Operation C-9
C.3.5 Pre-charge Contactor Sequencing During the Bridge Test
When the bridge test is commanded in register 100/1100, bit 2, the SB3000’s
pre-charge contactor will close. After the results of the test have been displayed on the
GDI module(s), the pre-charge contactor will be opened.
C.3.6 Charge Faults
The PMI Processor will generate a Charge Fault (register 202/1202, bit 6) if:
• the pre-charge contactor is closed when it should be open.
• the pre-charge contactor opens without being commanded to open.
• the pre-charge contactor is commanded to open and it does not open within one
second.
C.4 Line Synchronization
The motoring operation of the SB3000 Power Module is analogous to the operation of
an SA3000 Power Module regenerating power from a large synchronous motor to the
DC bus. For the SB3000 Power Module, the AC line acts like a very large synchronous
motor operating at a fixed frequency/speed. Whether the SB3000 Power Module is
motoring (supplying power to the DC bus from the AC line) or regenerating (returning
power to the AC line from the DC bus) is determined by the voltage level of the DC bus
which the SB3000 Power Module is regulating. To operate, the SB3000 Power Module
must be synchronized, in frequency and phase, with the AC line. Line synchronization
specifications are provided in Appendix A.
Phase synchronization is maintained by the PMI and the Line Synchronization
module. The period of the AC line is used to determine the frequency to command and
the offset between the zero crossing of the AC line and the commanded zero crossing
is used to determine the angle offset.
The Line Synchronization module, located in the SB3000 control cabinet, is connected
to the +/- 24 and 15 volt power supplies. The AC line synchronization circuit monitors
the AC line feeding the SB3000 Power Module and outputs a pair of signals locked
in-phase with the AC line to the A-C Power Technology module in the PMI rack. The
AC line synchronization circuit also contains the Burden resistor for the Hall device
which monitors the DC bus current.
If the PMI detects AC input voltage to be less than 75% of the configured voltage or
greater than 125% of the configured voltage, it will latch the WRN_PWR@ warning bit
and disable the firing of the IGBTs. If power is restored within ten seconds, the PMI
will re-synchronize and resume operation. If power is not restored within ten seconds,
the PMI will latch the FLT_PWR@ fault bit and will not automatically restart.
If input voltage is out of tolerance, a bit is set in the UDC Module’s memory
(VDC_SB@) to indicate that the voltage loop is in standby. The master speed
reference task can then optionally begin to decelerate the inverter-driven load, using
the inertia in the driven load (motor and machine) to maintain the DC bus voltage until
power comes back or the machine is stopped. If any fault is detected while in standby,
VDC_SB@ is turned off, and the drive will not automatically restart.