Rockwell Automation SB3000 AC Power Modules - Manual (Page 15)

Power Module Description 2-3
2.2 Electrical Description
AC power to the SB3000 Power Module is supplied from an AC power distribution/
soft-charge cabinet through the AC input reactor.
The DC bus voltage is filtered by the electrolytic capacitors. Discharge resistors are
designed to discharge the capacitors down to 50V DC within 5 minutes after power is
removed from the input terminals. However, the user should wait ten minutes before
working on the unit. Be sure to look at the built-in DC Bus Voltage meter and then
measure the DC bus potential before touching any circuitry.
When AC power is applied to the SB3000 Power Module’s input terminals 181(L1),
182(L2) and 183(L3), the DC bus is charged through the IGBT emitter-collector diodes
to the level of the rectified AC line voltage. See figure 2.1 and figures 2.5 to 2.13.
Charging current is limited by the separately-mounted soft-charge resistors and the
impedance of the AC input line reactor. Upon reaching the programmed level of DC
bus voltage, the pre-charge resistors are bypassed by the pre-charge contactor, which
places full line voltage across the AC line to the SB3000 Power Module.
The SB3000 Power Module’s inner control loop is enabled when the application task
sets register 100/1100, bit 0, (VDC_RUN@). When this is done, the PMI Processor
checks the interlocks as described in Appendix D. If the interlock conditions are
satisfied, the DC bus voltage is ramped from the voltage produced by the diode
rectification of the AC line voltage to the voltage reference value provided by the
programmed outer control loop. The DC bus voltage is then regulated by the on-board
voltage regulator. The ramp rate is 100 volts per second. When the preset reference
voltage is reached, register 200/1200, bit 10, (VDC_ON@) is turned on to indicate that
the Power Module is operating.
!
ATTENTION: DC bus capacitors retain hazardous voltages after input
power has been disconnected. After disconnecting input power, wait ten
(10) minutes for the DC bus capacitors to discharge, then look at the
built-in DC bus voltage meter. When the voltage is down to approximately
zero (0) volts, open the cabinet doors and check the voltage across the
DC bus bars, 1247 A,B,C (+ bus) and 1145 A,B,C (- bus), with an external
voltmeter to ensure the DC bus capacitors are discharged before
touching any internal components. Failure to observe this precaution
could result in severe bodily injury or loss of life.
Figure 2.1 – DC Bus Voltage
Power
On
Vac ∗ 1.414
OVT_E0%
UVT_E0%
VDC_RUN
VDC_ON