INTRODUCTION

The DECS-400 Digital Excitation Control System is a microprocessor-based controller that offers

excitation control, logic control, and optional power system stabilization in an integrated package. The

DECS-400 controls field excitation by providing an analog signal used to control the firing (output) of an

external power bridge. The DECS-400 monitors generator or motor parameters and acts to control, limit,

and protect the machine from operating outside its capability.

The optional, onboard power system stabilizer is an IEEE-defined PSS2A, dual-input, “integral of

accelerating power” stabilizer that provides supplementary damping for low-frequency, local mode and

power system oscillations.

Integral programmable logic provides excitation system control and annunciation based on DECS-400

contact inputs, operating mode status, excitation system parameters, and user-defined programming.

Setup and initial operation are facilitated by Basler Electric’s user-friendly BESTCOMS PC software that

incorporates a test mode, flexible oscillography, and a graphic display of PSS test results.

The DECS-400 is designed for use with Basler Electric’s Interface Firing Module (IFM) and SSE or SSE-N

power bridges. However, it will work equally well with any power bridge with a firing circuit that is

compatible with the control signal output of the DECS-400.