CERN Accelerating science

Article
Title	PEP-II Large Power Supplies Rebuild Program at SLAC
Author(s)	de Lira, Antonio C ; Bellomo, Paul ; Lipari, James J ; da Silva Rafael, Fernando
Affiliation	(SLAC)
Publication	2005
In:	21st IEEE Particle Accelerator Conference, Knoxville, TN, USA, 16 - 20 May 2005, pp.3685
Subject category	Accelerators and Storage Rings
Abstract	At PEP-II, seven large power supplies (LGPS) are used to power quad magnets in the electron-positron collider region. The LGPS ratings range from 72kW to 270kW, and were installed in 1997. They are unipolar off-line switch mode supplies, with a 6 pulse bridge rectifying 480VAC, 3-phase input power to yield 650VDC unregulated. This unregulated 650VDC is then input into one (or two) IGBT H-bridges, which convert the DC into PWM 16 kHz square wave AC. This high frequency AC drives the primary side of a step-down transformer followed by rectifiers and low pass filters. Over the years, these LGPS have presented many problems mainly in their control circuits, making it difficult to troubleshoot and affecting the overall accelerator availability. A redesign/rebuilding program for these power supplies was established under the coordination of the Power Conversion Department at SLAC. During the 2004 accelerator summer shutdown all the control circuits in these supplies were redesigned and replaced. A new PWM control board, programmable logic controller, and touch panel were all installed to improve LGPS reliability, and to make troubleshooting easier. In this paper we present the details of this rebuilding program and results.