Rockwell Automation SA3100 AC Power Modules - Manual (Page 17)

Power Module Description 2-3
2.2 Electrical Description
On AC input Power Modules, three-phase input power is applied through terminals
R-L1, S-L2, and T-L3. A current transformer is used to sense ground faults. The AC
input voltage is converted into DC voltage by a three-phase full-wave rectifier bridge.
See Appendix B.
On small (B frame) common bus Power Modules, the negative DC bus is applied to
the R-L1 input (TB1-5). The positive DC bus is applied to the T-L3 input (TB1-7). See
figure 3.7 and Appendix C.
On C frame and larger common bus Power Modules, the DC bus is connected directly
to the DC+ and DC– terminals on terminal block TB1. See figures 3.8 to 3.10 and
Appendix C.
With power applied, the internal DC bus begins charging through the pre-charge
resistors. Once the DC bus capacitors are fully charged and all pre-charge criteria are
met, the pre-charge SCR is gated, bypassing the pre-charge resistors. Operation of
the various pre-charge circuits is described in Appendix E.
The DC bus voltage is filtered by the electrolytic capacitors and is fused by fast-blow
fuses. Discharge resistors on the DC bus capacitors will discharge the capacitors
down to 50 VDC within 1 minute after power is removed from the input terminals.
The rectified, filtered DC voltage is fed to the inverter which produces the
variable-voltage, variable-frequency output to the motor (terminals U, V, W). The
inverter IGBTs are switched by the gate driver circuit under the command of the AC
power control section of the PMI Regulator. Three Hall-effect devices (two on the
output and one on the DC bus) provide current feedback to the PMI Regulator. AC
output power inductors limit the magnitude of di/dt on the U, V, and W terminals.
Refer to Appendices B and C for schematic diagrams of the SA3100 Power Module.