Modern DC Drive and Control System

The new bridge control system consists of one operator control desk and one main control panel. The desk is used in conjunction with the panel to issue commands in order to change traffic lights, operate traffic gates, engage the centerlock, and command North and South leaf motion. Systems Interface not only manufactured the new DC motor drive system, but
also designed it.

The DC motor drives consist of two leaf drive/control systems. One system controls the South
bridge leaf and the other system controls the North bridge leaf. The North and South leaf drive
systems are virtually identical. Each leaf drive cabinet houses two Siemens 75 HP DC four
quadrant (reversing/regenerative) digitally controlled SCR motor drives, isolation transformers,
tachometers, overspeed switches, limits interface, brake interface and logic/sequence controllers
to interface between the motor drives and the bridge control system. The leaf drive systems are
connected to the existing 65 HP Westinghouse series wound DC motors (two motors per leaf).

In addition, two separate Siemens 75 HP single quadrant
(nonregenerative) SCR drives have been integrated into each leaf drive system. These drives are used to separately excite the DC motor series fields.

The public will now benefit from the completion of this fully functional operation system. Systems Interface successfully integrated the project pieces together in the best way to serve the WSDOT and the public who own the bridge. March 31, 2000 marked its first successful test run. WSDOT personnel were on hand to witness the feat of engineering that brought this historic bridge into the 21st century.