Alternator control system for the Alcator C-MOD tokamak

The Alcator C-MOD tokamak can expend over 500 MJ in a single pulse. The primary power source for this experiment is the upgraded Alcator C alternator. Over the years the alternator has undergone several modifications to make it more suited for pulsed operation and in the near future the energy storage of this 40 year old alternator will be increased from 500 MJ to 2000 MJ with the addition of a 75-ton flywheel. After 25 years of utility service and 8 years of pulsed operation the alternator is still in good condition. However, in order to insure many more years of reliable service every effort must be made to reduce electrical, thermal and mechanical stresses. This means the alternator must be interlocked with the power supplies (7 in all) so that it can protect itself from excessive armature current should any one fail. It also necessitates monitoring many of the critical temperatures, pressures and safety backup systems so that either operator intervention or an orderly shut-down can prevent serious problems. This report will describe how the Alternator control system has been modernized with the addition of a Programmable Logic Controller (PLC) in conjunction with a networked, PC based Supervisory Control And Data Acquisition (SCADA) package. The report will discuss the design, commissioning and operational experiences of the new control system