Basler Electric DIGITAL EXCITATION CONTROL SYSTEM DECS-300

requirements. Var/power factor controllers are available for operating the generator in parallel with a utility.

Another feature is the user selectable, 20 standard pre-programmed stability settings for exciter field

applications, 20 standard stability settings for main field applications, and one user programmable stability

setting. It has programmable output contacts for annunciating the various DECS-300 operating and

protection features. DECS-300 can be programmed to operate safely in the event of loss of sensing.

For critical applications where the failure of the excitation system keeps the generator from operating, a

redundant DECS-300 can be used to provide back-up excitation control. Redundant excitation systems

need to be properly designed to allow for proper removal of the failed system and also for the proper

enabling of the back-up system. Provisions also have to be made for the periodic checkout of the back-up

system to insure it is operational and can be put into service without warning. DECS-300 allows for

excitation system redundancy by providing automatic tracking and transfer between control modules. In a

single DECS-300 application, the DECS-300 can be selected to allow the inactive operating modes of the

DECS-300 to track the active operating mode. If the excitation system is normally operating on-line in the

automatic mode and a loss of sensing occurs, the unit could be changed to the manual mode of operation

where the loss of sensing has no impact on the exciters ability to provide proper levels of excitation. While

performing a routine maintenance checkout of the DECS-300 in back-up mode, the internal tracking feature

allows a transfer to an inactive mode that will result in no disturbance to the system. DECS-300 also

provides for tracking between DECS-300 units. The back up DECS-300 unit can be programmed to

designate any of the operating modes to track the primary DECS-300 operating mode.

DECS-300 is Modbus™ compatible via the RS-485 port. For more information about Modbus™, see

Section 7 in this manual. The front panel RS-232 communications port supports the BESTCOMS PC

software. BESTCOMS allows for user-friendly programming of setpoints and ranges, and allows for step

changes to facilitate proper stability programming. BESTCOMS provides easy start/stop control and

operator adjustment of the excitation system with real-time metering. The software catalog number is

BESTCOMS-DECS300-32. BESTCOMS is provided with the DECS-300 as part of the software/manual

package.