LCLS Magnet Meeting Minutes - 4/14/2006

From: "Luchini, Kristi" <luchini@slac.stanford.edu>
Subject: LCLS Magnet Meeting Minutes - 4/14/2006
Date: Mon, 17 Apr 2006 08:56:58 -0700
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LCLS Magnet Meeting
Date: Friday, April 14, 2006
Time: 10am
Location:  Palisades Conference Room bld 280B rm 
Attendees: Patrick Smith, Roger Carr, Bob Fuller,  
           Paul Bellomo, Kristi Luchini

Agenda: Magnet Interlocks - Klixons 

Minutes:

A standard SLAC method used for magnet interlocking does not exist. For example, SPEAR 3 currently uses Klixons and PLCs for magnet interlocking large intermediate and MCOR powered magnets. All of the SPEAR 3 magnets (including the correctors) are water-cooled. PEP II uses two different methods for interlocking magnets.

Method 1 - For large and intermediate power supplies that power a single magnet, the Klixon connects directly to the BitBus controller to turn off the power supply in the event of over-temperature.

Method 2 - For large series-connected magnet strings powered by the chopper power supplies in B685, the Klixons connected in a bridge arrangement connect to specially designed interlock chassis. The bridge networks identify the location of an overheated magnet.

Note that the PEP II MCOR12s only power air-cooled, non-interlocked corrector magnets.

LCLS has both water-cooled and air cooled magnets. There are three locations for magnet loads powered by MCORs. The first two locations are the LINAC and the Injector where the magnet currents are 18A maximum and typically run at 15A. The third location is the LTU, where typically the magnets of concern may run as much as 25A. The temperature that these magnets can go up to or the delta T, is 25deg C.

The Intermediate Ethernet PS controllers (EPSC) accept a Klixon input. LCLS uses the EPSCs for the following magnets:

Injector:	BX01-BX02, BXH1-4, BXS, S1 and S2
BC1:		BX11-BX14

MCORs power magnets that run at lower currents, 12A, or 30A. The MCORs not have a Klixon input. However, the MCOR power modules do have an output over-current limit. The over-current limit is not programmable. Therefore, it is possible that an MCOR will drive a magnet the maximum limit, 12A, or 30A depending on MCOR type used. These currents may drive the magnet beyond its maximum limit. LCLS will set software limits in the EPICS database for all controllable magnets to limit what an operator can set the magnet current.

Klixons will interlock water-cooled magnets against over-temperature. Software set-point limits in the EPICS database will protect air-cooled magnets.

The hazards that are of concern:
1) Air or water-cooled magnet overheating to the point of magnet destruction
2) Boiling water, which creates steam and burst hoses
3) No water, or no water flow, in the system to cool the water-cooled magnets

The list of water cooled magnets that will require Klixons are listed below:

December 1, 2006 Commissioning
--------------------------------
  Injector: BXS, BXG main, BX01-BX02, SOL1, SOL2, QB
  BC1:      BX11-14

2007 Commissioning
-------------------
  QG01, QG02, QG03
  QA01, QA02
  QE01, QE02, QE03, QE04

Trim coils will not require Klixons.

The magnets of concern listed above for the December 2006 commissioning, BXS, BXG main, BX01-BX02, SOL1, SOL2 and BX11-14, are powered from intermediate power supplies while the QB magnet is powered from an MCOR. All intermediate power supply controllers provide a klixon input while the MCOR system does not.  

The cables for the Injector intermediate ps in the injector have been scheduled to be pull in Phase I (April 2006). The injector intermediate cables for Klixons are scheduled to be pulled for Phase II (August 2006). The cables for Klixons related to those magnets powered by MCORs will be added to this Phase II cable pull.

Roger Carr will verify that the BXG main magnet is water-cooled.

LCL personnel will consider implementing temperature protection with a programmable logic controller (PLC) for water-cooled magnets, using database software limits as a secondary level of protection. LCLS will use software limits for all magnets.

The Klixon opening temperature is 175degF (80degC).

SOL3 will also need a Klixon during 2009 installation.

Water flow switches also need installation. Since flow switches are a maintenance headache, the recommendation is for one monitored main flow switch for all systems. The return line is the typical placement for this flow switch to indicate if water is not flowing due to a leak or other reason.

In summary, LCLS will pull cables from the magnet Klixons to the injector intermediate ps controllers (see above) during the Phase I installation in April 2006. LCLS will pull a cable to connect the QB magnet Klixon to a PLC, or other protective device, during the August 2006 Phase II installation.

LCLS purchased an inexpensive micro-PLC system, an IDEC Smart-Relay for the MCOR Ground Current Monitor System. It is possible to combine the MCOR Ground Current Monitor System with MCOR Klixon interlocking by use of an existing, unused Allen-Bradley PLC. We already posses existing EPICS software to implement PLC control. The PLC-based Klixon interlocking scheme could serve as a model for other LCLS subsystems, such as Vacuum and PPS. CPE can program the PLCs. SPEAR 3, PEPII, and the Damping Ring RF systems set precedents for using Allen-Bradley PLCs for interlocking. Several people at SLAC have experience using PLCs for interlocking.
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