BYPASSING & ISOLATING
(continued)
3 --- 4
4. Open the lower enclosure door. Pull out both left and
right side rails then use the twohandles to roll out the
transfer switch. It can be safely inspected in this
position. The t ransfer switch can also be removed for
easi er maintenance operati ons. See Figure 3–13.
Hazardous voltage capable of causing
electrical shock, burns, or death;
do not touch any control circuit terminals.
right rail
left rail
handles
Figure 3–13.Transfer switch isolated
and pulled out for inspection.
See page 2–2 for maintenance handle use. A lift ing yoke
734408 is available to facilitate lifting by using an
overhead crane or similar equipment. See WARNING.
The Transfer Sw it ch weigh s 165–235 lbs.
dependi ng upon th e number of poles. Use lift i ng
devi ce 734408 or oth er devic e capable of lifti ng
this weight to avoid personal injury or equipment
damage. Two persons are recommended.
Contact Inspection
The main contacts are protected by arcing contacts.
The arcing contacts make first and break last to
avoid arcing at the main contacts. Contact condition
should be checked annually. Contacts should be
replaced when contact material becomes severely
worn. Discoloration is normal. Do not file contacts
because it wastes material. Instead use light emery
paper to clean up the contact surfaces.
If the contacts need to be replaced see page 2–2.
To prevent the possibility of fatal electrical
shocks and burns, bypass, isolate, and withdraw
the transfer switch before working on it.
The contact assemblies (two for each pole) are
located to the right of the operator mechanism.
1. Deenergi ze transfer switch (pages 3–1 thru 3–4)
Bypass, isolate, and withdraw transfer switch.
Use a voltmeter to verify that no electrical
power is present at the transfer switch terminals.
2. Use the maintenance handle (page 2–2).
Open the contacts that will be inspected by using
the detachable maintenance handle.
3. Removetheinterphasebarriers(Figure 3–14).
Use a blade screwdriver to loos en (ccw) four
round–head screws holding each barrier to the
arc chutes. Slide barrier up until keyholes clear
the round–head screws, then remove it.
loosen (ccw)
round–head screws
(do not remove)
interphase barrier
arc chutes
keyslots
loosen (ccw)
round–head screws
(no not remove)
keyslots
insulator nuts
Figure 3–14. Interphase barrier removal.
4. Remove the arc chutes.
Use a 5/8” nutdriver to remove (ccw) two long
insulator nuts. Then pull the arc chute outward
(off the long threaded rods). See Figure 3–14.
(20 Seiten)
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