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Magnet Power Supply Reliability at the Advanced Photon Source*
| Content Provider | Semantic Scholar |
|---|---|
| Author | Hillman, Anthony Carwardine, Josie Sprau, G. |
| Copyright Year | 2001 |
| Abstract | Operational goals for the Advanced Photon Source facility include 95% user availability and a mean time between unscheduled beam losses of 30 hours, with 5,000 user hours of scheduled beam per year. To meet these goals, operational goals for the magnet power supply system have been set at 99% availability, with a mean time between faults of 200 hours. The large number of power converters (1,400 in the storage ring alone), complexity of the overall systems, and limited machine shutdown time make meeting these goals particularly challenging. During fiscal year 2000, power supply system availability was close to 99%, but the mean time between faults was only 85 hours. Efforts are ongoing to incrementally improve power supply reliability and to meet the operational goals. This paper presents important power supply operational statistics and describes our approach to meeting the reliability goals. 1 OVERVIEW The Advanced Photon Source (APS) storage ring contains some 1,400 power supplies. Each multipole and corrector magnet is separately powered, with only the main dipole magnets on a common bus [1]. The separate power supplies provide increased flexibility for the storage ring, but place additional demands on power supply reliability. The APS reliability goals are 95% availability and 50 hours mean time to unscheduled beam loss, with 5,000 user hours scheduled per year. The present annual operating schedule provides for four user runs (typically 7 to 10 weeks long), and four machine shutdowns (typically 3 to 5 weeks long). There is one 48-hour period and one 8hour period of machine studies/intervention for every two weeks of user operation. Reliability goals for the magnet power supply systems are 99% availability, with a mean time between beam losses of 200 hours. Because a failure of any one magnet power supply can cause loss of stored beam, this goal translates to a required mean time between power-supplyrelated beam trips (MTBF) of better than 250,000 hours for each magnet power supply. In the past, the power supply systems have not consistently met these goals, and efforts are ongoing to improve reliability. *Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. Hillmana@aps.anl.gov If we average the power supply downtime since the start of calendar year 2000, we are very close to our target goal. The implementation of such improvements is particularly challenging because of the number of power supplies involved, and because of the potential to create new problems by simply disturbing the equipment. Statistical data on power supply reliability comes from two sources. First, detailed records are maintained by APS Operations Groups to keep track of reasons for lost fills and machine downtime. Second, the APS Power Supply Group maintains detailed information on equipment failures and repairs. Although machine availability and mean time to beam loss (fault rates) are both key performance indicators, most of the discussion in this paper concerns faults that have a direct effect on machine availability. Table 1 shows yearly power supply (PS) reliability statistics for fiscal year 1998 to 2001 with power supply downtime percentage of delivered beam time, MTBF, and mean time to repair/recovery (MTTR). For the past two years, downtime has been close to the goal of 1%, but MTBF has been significantly below our goal of 200 hours. More detailed run-by-run statistics are shown in Figures 1 and 2, together with trendlines that use a moving average of four runs. Again these data show that overall power supply downtime has been close to the goal of 1%, but the MTBF is below our stated goal. Table 1: Power Supply Overall Statistics PS Downtime (%) MTBF (Hours) MTTR (Hours) FY98 1.93% 118.95 2.47 FY99 1.37% 89.96 1.30 FY00 0.96% 86.36 0.88 FY01 1.04% 142.84 1.55 0-7803-7191-7/01/$10.00 ©2001 IEEE. 3657 Proceedings of the 2001 Particle Accelerator Conference, Chicago |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://accelconf.web.cern.ch/accelconf/p01/PAPERS/FPAH002.PDF |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
