COMPLETE LIST OF BELOW ITEMS AVAILABLE FROM THE FNAL STOCKROOM

(URGENT NOTE: Due to a redesign of the power bulkhead, users are urged NOT to use T&B PN54112 connectors for these cables, due to variations in the maximum widh of the connector tongue, which in many cases exceeds the maximum allowable width of the opening on the bulkhead for the connector.)

 AUXILIARY POWER BUSSES
For the remaining busses (16 cables typically), which can carry up to 60A, users are requested to use 6 AWG neoprene insulated stranded welding cable.  This cable is a stock item in the FNAL stockroom (1170-0810),  but can be ordered from outlets such as McMaster-Carr (PN 7940A21).   The crimp-on connectors for this size cable are manufactured by Thomas & Betts (PN 54105) and have a blue color code banding printed on them.  The lugs are available in the FNAL stockroom (1110-0260).   If needed, the user can special order a 90 degree version of this connector from T&B by ordering the following part number: 54105UB.

CABLE-TO-CABLE SHORT CIRCUIT PROTECTION
Users are encouraged to install a piece of heat shrink tubing over the crimped portion of the connector, extending at least 1-1/2" onto the insulation of the cable to reduce the possibility of shorting power cables together should they shift do to loosening of the power lug nuts on the subrack.  The heat shrink material needs to be slid onto the cable prior to crimping the connector onto the cable.  Heat shrink tubing is available in the FNAL stockroom in various sizes and color.  The Equipment Support Department has found that 1" shrink tubing, available from the FNAL stockroom (Clear, 1130-4580; Black, 1130-4600; Red, 1130-4620), works best with 3/0 AWG welding cable, while 3/8" tubing (Clear, 1130-4340; Black, 1130-4320; Red, 1130-4360; White, 1130-4380) works best with 6 AWG welding cable.

CONSTRUCTING POWER CABLES
The cable cutter, crimping tool and dies for the crimp-on connectors ARE NOT available from the FNAL stock room.  They can be ordered from T&B or their local retail vendor.  It is suggested that users use the following T&B Part Numbers when ordering this tooling.

2. Slide section of heat shrink tubing over insulation.  Use at least 2-1/2" for 4/0 cable, 1-1/2" for 6 AWG cable.

3. Strip back cable insulation an appropriate amount for the connector to be used. (7/8" for 4/0, 1/2" for 6 AWG).

 
 
 
 
 
 
 

4. Slide connector(s) onto stripped portion of cable until the cable end meets with cable stop/crimp inspection window.

5. Crimp the connector(s) onto the cable with the crimping tool, making sure cable is in line radially with the connector.  Line up crimper jaw faces between the color code banding on the connector.  The purple connectors need to be crimped at 2 points, the blue connectors at 1.

6. Slide shrink tubing up over the connector to the edge of cable stop/crimp inspection window.

7. Holding cable and connector in line, heat shrink tubing to snug fit around connector and cable. (See example here)

ATTACHING POWER CABLES TO POWER LUGS

Due to the design of the subracks, power cables are required to attach to the subrack from above.  This is opposite of the above graphic.  This allows full access to the transition modules.

The use of both the flat and compression washers, as described in the graphic above, is required.  The convex side of the compression washer must face away from the subrack.  Use of a standard lock or star washer will damage the brass nut.  The compression washer may need to be replaced if the cable is disconnected from the subrack.

When attaching power cables to the subrack power lugs, it is important not to over tighten the nuts and strip the lugs.  The maximum torque to be applied to the +5v and +3.3V lug nuts is 135 in-lbs (15.25 N-m).  These nuts require use of a 17mm socket.   Maximum torque for all other lug nuts is 45 in-lbs (5.08 N-m).  These nuts require use of a 10mm socket.  A label stating these torque limits is attached to the inside of the rear of the subrack and seen below. The FERMI Stockroom does not stock torque wrenches.  These are available from various outside sources, such as Harbor Freight Tools or W.W. Grainger, Inc.

ALTERNATE TORQUING PROCEDURE IF TORQUE WRENCH IS NOT AVAILABLE
Install washers as indicated in above diagram, but add an additional flat washer between the compression washer and the nut.  While tightening nut, watch space remaining between compression washer and outer flat washer.  Tighten until space between the two washers is eliminated.

POWER SUPPLY SENSE CABLE
This shielded cable connects from the 26 position "D" connector located in the middle of the subrack power bulkhead to the power sense connector on the power supply chassis.  The shielding is provided to reduce radiated electrical interference on the sense lines.  To achieve this, the shield must be connected only on the subrack end.  Connecting the shield to both the subrack and the power supply chassis will induce signals on the sense lines which will interfere with the quiet operation of the power supplies.

Current Capabilities and Torque Specifications

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