Rockwell Automation 1395 Digital DC Drive FRN 5-10.10/9.30 - Manual (Page 45)

Chapter 3
Hardware Description
40 – 100 HP, 230VAC
75 – 200 HP, 460VAC
3-5
Field Bridge Components A general description of the components in the field bridge (Fig. 3.4) and
their operation is covered here:
Supply Voltage – In addition to being used for synchronization, the
three-phase voltage from fuses F4, F5 and F6 is sent to TB1 where two of
the three phases are routed to the input of the field supply power bridge
(labeled Field L1 and Field L3 on Figure 3.4).
Field Current Feedback – Current transformer FCT provides field
current feedback information to the feedback board at TB8 and 9. The
feedback board rectifies the single phase feedback and scales the DC
voltage using a burden resistor selected by the position of Jumper J1 on the
feedback board before being sent to the power stage interface. The DC
voltage representing field current feedback is passed directly through the
power stage interface and sent to the main control board.
Surge Suppression – Surge suppressor 3MOV protects the field power
bridge from high voltage line spikes and line surges on the incoming AC
line. 2MOV protects the motor field windings from line spikes on the
output of the field bridge.
Line Choke – Line Choke CH8 protects the field power bridge SCRs
from rapid rate of current changes.
SCR Modules – Field bridge SCRs are contained in modules made up of
two SCRs per package (PM7 and PM8).
Field Pulse Transformer and Snubber Board – The Field Pulse
Transformer Board provides the gate firing pulses and switching voltage
transient (dv/dt) protection for the field SCRs.
Bridge Output Connections – The output of the field bridge is connected
to TB2-1 and 2 which in turn is connected to the field leads of the motor.
The terminal labeled F+ on TB2 is connected to the F1 lead of the motor
and terminal F- to the F2 lead.