Development of PLC based chiller control system for 3 MeV DC electron beam accelerator

A 3 MeV DC electron beam accelerator is under development at Electron beam center, Kharghar, Navi Mumbai. The accelerator has various sections, where heat is generated during operation due to factors contributed by efficiency. The areas that produce heat such as beam dump, HV oscillator, scan horn region etc need to be cooled. A 5TR chiller unit has been installed in a room in the vicinity of the accelerator. Standard chiller unit available in the market do not provide a remote control interface, instead they provide on panel local controllers for the operation of the system. A PLC based interlock has been developed to control all the chiller components such as Cooling tower fan, cooling tower pump, ON/OFF operation of compressor etc. All the components used in chiller unit are interfaced to PLC besides temperature sensor. All machine safety interlock have been introduced by using suitable hardware such as antifreeze coil used to trip compressor in case of control failure may make the ice of water being cooled. The operating point of the chiller has been set to provide water 22-24 degree C. The PLC has been programmed using ladder logic programming method. The system is fully automatic. The system can be operated by setting the set temperature say 22 degree C and temperature hysteresis say 2 degree C. Pressing start button operates different units of the system automatically. Its starts the compressor when the water temperature is 22+2 degree C and stops the compressor when temp reaches at 22 degree C. Any unexpected failure such as 3Phase sequence change/phase failure, over load relay trip, excess temp are indicated by a hooter sound along with fault display on the HMI. A touch screen panel has been provided for human machine interface. This development of control system for chiller sub-system of accelerator has helped us in bringing the chiller unit control from the control room using Ethernet link using Modbus TCP-IP. The implementation of PLC controlled chiller control has helped us in making seamless integration of chiller operation with the operation of high voltage systems. (author)