Vacuum-pump control system using programmable logic controllers on the TCP/IP network for the 2.5-GeV storage ring

A vacuum-pump control system has been developed using programmable-logic controllers (PLC) for the 2.5-GeV storage ring at the Photon Factory, High Energy Accelerator Research Organization (KEK). There are sixty-six Ti-getter vacuum pumps at the storage ring. Evacuation of gases in the storage ring is done by controlling the current in the titanium filaments in the vacuum pump (max 50 A). A PLC has a TCP/IP network port, 16-bit-digital output ports connected to sixteen solid-state relays (SSR) for current control. The PLC can simultaneously control up to sixteen pumps. These vacuum pumps are connected to SSRs which chop the AC current so as to control the current in the pumps. To operate the pumps, the pump current must have a trapezoidal-shaped current form. The PLC is configured so that the current in the pumps has a trapezoidal form associated with pre-heating, evacuation, and cooling-down phases of the pump. PLCs are connected to a personal computer (PC) through the network. The PC can automatically control the PLCs by sending a set of commands through the TCP/IP network. The commands specify the duration of the current form. Upon receiving a command from a PC running under WindowsNT through the network, the PLC generates pulse-trains through the digital output ports to trigger the SSRs in association with the operating phases. The design of the vacuum-pump control system is discussed.