Rockwell Automation SD3100 DISTRIB PWR SYS SD3100 DC PWR MODULE - Manual (Page 21)

Mechanical/Electrical Description 2-7
• Gate Coupler Cards
Gate coupler cards amplify the gate signal pulses from the DC Power Technology
module to trigger the SCRs. In addition, these cards provide gate driver isolation
from the control circuits in the PMI rack.
• Main DC Contactor
The main DC contactor is used to isolate the DC motor armature and to interrupt
the DC current to the motor armature. Coil voltage to the contactor is controlled by
contacts from the pilot relay.
2.1.2.3 Field Power Module Components
The Field Power Module operates on single-phase AC, which must be taken from the
three-phase armature power bridge’s L1 and L3 input lines. The incoming AC must be
supplied to the Field Power Module through an isolation transformer.
The Field Power Module rectifier consists of 8 SCRs in two full-wave bridges,
connected in anti-parallel. Snubber protection is provided to permit operation on a
common bus with other Power Modules. A Hall effect device is used to monitor the DC
output current.
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2.2 Electrical Overview
SD3100 DC Power Modules convert fixed voltage and frequency three-phase AC
power to adjustable voltage DC power for motor armatures, fields, or other
applications that require controlled DC power. Power Module operation is
programmed and controlled in the UDC module in the AutoMax rack and the PMI
Processor in the drive’s internal PMI rack.
Incoming power is supplied from a three-phase AC line. A phasing transformer
provides AC line sequencing and zero-crossing information for each input phase to
determine when SCRs should be fired. The Power Module is capable of auto-phasing
under software control and can adapt to ABC or ACB phase rotation.
The non-regenerative Power Module rectifier consists of 6 SCRs, configured in a
full-wave power bridge. The regenerative Power Module rectifier consists of 12 SCRs
in two full-wave bridges, connected in anti-parallel. Snubber circuits provide dv/dt
protection for the SCRs in each bridge leg.
The firing angle for each SCR is determined by the current regulation algorithm
executing in the PMI Processor. SCR gating signals are provided by the DC Power
Technology module, under the control of the PMI Processor. The gating signals and
firing angles are synchronized with the AC line. The PMI Processor regulates the
current for the application by varying the point in the AC line cycle at which forward
SCR conduction begins. The PMI Processor receives the current reference from the
UDC module in the AutoMax rack. The UDC runs the application task that provides
overall control of the Power Module.
The three-phase SCR power bridge in a non-regenerative Power Module controls
forward rotation (motoring) only. Torque is in the same direction as rotation.