[Halld-controls] More on Director's Review and Lehman Review recommendations for Hall D solenoid controls

[Elliott Wolin]

Hi,

Some comments on the recommendations (see my prevous email below), based 
on discussions with George and Paul Brindza, experience during the test, 
etc. 

Note that some of the recommendations aim at ensuring we can perform a 
fast dump when we need one, and others are there to ensure we do not do 
a fast dump when we don't want one (e.g. loss of power).  I'm not sure 
we are worried about the occasional fast dump under e.g. a loss of power 
scenario...the magnet seems quite robust and fast dumps apparently are 
no problem.  I suspect this concern was based experience on a different 
kind of magnet, one where fast dumps are truly fast (seconds instead of 
20 minutes), and you really do not want to fast dump if at all possible.

(I comment in order on the items from my earlier email, see copy below)

- George says forget the cold diodes, certain failure scenarios could 
lead to extremely unbalanced forces between the coils.

- We installed a fast DAQ in the coil test and we are improving it for 
the final system.

- We routinely check for shorts, ground faults, etc. as part of our 
installation and startup procedures.

- Paul says adding a second dump breaker may not require a new power 
supply, but it will involve major (heavy!) rewiring and an additional 
cabinet and large, high current switch.

- Adding more diodes to the existing power supply may be problematic 
since it's pretty full in there.  Currently there are three diodes and 
Paul says two could handle the dump current, and even one could but it 
might get damaged.  I'm not sure if additional diodes could reside in a 
new cabinet if we add a second dump breaker.

- If the Danfysik QD will work (i.e. if there is an acceptable 
inductance balance, Floyd will do the simulation this Fall) we could buy 
another one,  or build one using a different technology.  Concerning 
building one, the leading candidate is to use an FPGA-based system with 
A/D's on the front-end and a relay on the back end.  Cody thinks it can 
easily be fast enough and should meet safety requirements, and it's not 
particularly difficult to build.  Will our consulting magnet engineers 
approve an FPGA-based quench detector?

- Mark will look into whether we can build the ground fault detector 
using the dump resistor.

- We are looking into whether the big counting house UPS can power the 
Danfysik control boards and contactor circuits.  I believe it could, but 
are we worried about avoiding a fast dump when the power goes out? 

- Glenn formed a committee to perform the FMEA.

Comments, thoughts, suggestions, words of wisdom...?

Thanks,



Elliott Wolin wrote:

Hi,

To my knowledge below are all the relevant recommendations for the Hall 
D Controls group concerning the solenoid.  There are others related to 
refurbishment, commissioning, cryo systems, engineering safety and the 
new solenoid. 

We need to address all of the items below even if we do not implement 
all of them.  Note that sometimes it's simpler to do what they recommend 
than to argue why we shouldn't.  Also note that some of them are already 
done or partly done:

   * determine if cold diodes can increase quench detection
   * add fast DAQ system prior to testing first coil
   * add tests for internal shorts, shorts to ground and ground faults
     in coil and power supply to start-up sequence
   * add second dump circuit breaker
   * add additional quench circuit diodes
   * add second quench detector (connected to second dump breaker)
   * add center tap to dump resistor and monitor ground current in the PLC
   * add UPS on dump breakers to avoid fast discharges
   * perform Failure Modes and Effects Analysis (FMEA)

We will discuss these in the every-other Tues morning Solenoid Controls 
Redesign meeting, and on occasion in the alternating every-other Thurs 
morning full Controls meeting.

Your thoughts and interpretations will be appreciated.

Thanks,

-- 

				Sincerely,
					Elliott


================================================================================


Those raised in a morally relative or neutral environment will hold
		    no truths to be self-evident.
				   

Elliott Wolin
Staff Physicist, Jefferson Lab
12000 Jefferson Ave
Suite 8 MS 12A1
Newport News, VA 23606
757-269-7365

================================================================================


-- 

				Sincerely,
					Elliott
 

================================================================================


 Those raised in a morally relative or neutral environment will hold
		    no truths to be self-evident.
				   

Elliott Wolin
Staff Physicist, Jefferson Lab
12000 Jefferson Ave
Suite 8 MS 12A1
Newport News, VA 23606
757-269-7365

================================================================================